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Use and control of ionizing radiations
Use and c o n t r o l of ionizing r a d i a t i o n s M a r i a n n e D. Woolgar*
T h i s a r t i c l e s u m m a r i z e s the m a i n p r e c a u t i o n s and c o n t r o l s f o r the m o r e c o m m o n u s e s of ionizing r a d i a t i o n s . The m a i n a i m of t h e l e g a l r e q u i r e m e n t s and r e c o m m e n d a t i o n s of the Code of P r a c t i c e i s to e n s u r e t h a t p e r s o n s working with ionizing r a d i a t i o n s do not r e c e i v e a dose of r a d i a t i o n in e x c e s s of t h e m a x i m u m p e r m i s s i b l e doses. All u s e r s should be fully a w a r e of t h e s e r e q u i r e m e n t s a n d if n e c e s s a r y s e e k e x p e r t a d v i c e b e f o r e u n d e r t a k i n g work with ionizing r a d i a tions.
During r e c e n t y e a r s t h e r e h a s b e e n a r e m a r k a b l e i n c r e a s e in the u s e of r a d i o i s o t o p e s and x - r a y equipment, and ionizing r a d i a t i o n s a r e now a v a l u a b l e tool in i n d u s t r y a n d r e s e a r c h and a r e b e i n g u s e d to e x a m i n e and i m p r o v e t h e quality of a v a r i e t y of p r o d u c t s and to obtain new knowledge about the m e c h a n i s m of c h e m i c a l , e n g i n e e r i n g and biological p r o c e s s e s . It i s h o w e v e r e s s e n t i a l that all u s e r s should b e a w a r e of t h e p o t e n t i a l h a z a r d s to h e a l t h t h a t can a r i s e f r o m t h e i r u s e if p r o p e r p r e c a u t i o n s a r e not taken. It is i m p o r t a n t t h a t t h e r e s h o u l d b e effective s u p e r v i s i o n to c o u n t e r r i s k s in t h e i r u s e a n d t h a t a r r a n g e m e n t s b e m a d e to keep in step with national legislation and international recommendations. MAIN USES X - r a y s have b e e n used for x - r a d i o g r a p h y for many y e a r s . Today, x - r a y s and )~-rays f r o m such i s o t o p e s a s cobalt 60, c a e s i u m 137 and i r i d i u m 192 a r e p r o b a b l y a m o n g the m o s t c o m m o n l y u s e d ionizing r a d i a t i o n s in i n d u s t r y f o r x and 7 r a d i o g r a p h i c e x a m i n a t i o n s of m e t a l c a s t i n g s , welds and f a b r i c a t e d m e t a l c o m p o n e n t s . X - r a y s a r e a l s o u s e d in i n d u s t r y f o r t h e f l u o r o s c o p i c e x a m i n a t i o n of v a r i o u s m a n u factured articles for checking correct assembly or detecting f o r e i g n m a t t e r . X - r a y c r y s t a l l o g r a p h y equipment, f o r such p u r p o s e s a s the a n a l y s i s of c r y s t a l l i n e s u b s t a n c e s , i s used to a l e s s e r extent in f a c t o r i e s , but h a s a wide application in r e s e a r c h . It s h o u l d not b e f o r g o t t e n t h a t c e r t a i n a p p a r a t u s u s e d in both i n d u s t r y and r e s e a r c h a l s o e m i t s ionizing r a d i a tions, a s in the c a s e of e l e c t r o n m i c r o s c o p e s , high power t r a n s m i t t i n g a n d r e c t i f y i n g v a l v e s , i m a g e i n t e n s i f i e r s and c e r t a i n cathode r a y tubes. In addition to the u s e of r a d i o i s o t o p e s f o r ),-radiography, the r a d i a t i o n s f r o m v a r i o u s i s o t o p e s a r e e m p l o y e d in a v a r i e t y of i n s t r u m e n t s a n d m e a s u r i n g d e v i c e s , s u c h a s t h i c k n e s s gauges, l e v e l gauges, package m o n i t o r s , s t a t i c e l i m i n a t o r s and c h r o m a t o g r a p h s . T h i c k n e s s gauges, f o r e x a m p l e , a r e u s e d in I n d u s t r y f o r m e a s u r i n g and c o n t r o l l i n g the t h i c k n e s s of m a t e r i a l s such a s sheet metal, plastic and paper. L e v e l gauges s i m i l a r l y employ r a d i o i s o t o p e s for m e a s u r i n g and c o n t r o l l i n g t h e l e v e l of c o n t e n t s in e n c l o s e d v e s s e l s . On the o t h e r hand, s t a t i c e l i m i n a t o r s a r e u s e d to d i s c h a r g e un o wanted s t a t i c e l e c t r i c i t y which a r i s e s in i n d u s t r i a l p r o c e s s e s s u c h a s p a p e r m a k i n g and in the m a n u f a c t u r e of textiles. The r a d i o i s o t o p e s u s e d for the p u r p o s e s a l r e a d y i n d i c a t e d a r e in the f o r m of what a r e known a s s e a l e d s o u r c e s . T h e r e a r e a l s o i m p o r t a n t u s e s of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s f o r e x p e r i m e n t a l work in f a c t o r y p r o c e s s e s and in r e s e a r c h projects.
* A d v i s o r y and I n f o r m a t i o n Unit, D e p a r t m e n t of E m p l o y m e n t and P r o d u c t i v i t y , B a y n a r d s House, 1-13 Chepstow P l a c e , W e s t b o u r n e G r o v e , Londc~ W2, England
A long known u s e of u n s e a l e d r a d i o a c t i v e s o u r c e s in i n d u s t r y i s in t h e p r o c e s s of l u m i n i z i n g . T h e r e a r e a l s o a few f a c t o r i e s in which o r e s a r e p r o c e s s e d f r o m which r a d i o a c t i v e m a t e r i a l s a r e p r e p a r e d in s u i t a b l e f o r m s f o r u s e in i n d u s t r y , and p a r t i c u l a r l y v a r i o u s a s p e c t s of r e s e a r c h . T h e r e a r e d i f f e r e n t t y p e s of i o n i z i n g r a d i a t i o n s with d i f f e r ing p r o p e r t i e s ; the ones m o s t c o m m o n l y u s e d a r e x a n d g a m m a r a y s , a n d a l p h a and b e t a p a r t i c l e s . A n o t h e r type of i o n i z i n g r a d i a t i o n , n e u t r o n s , although u s e d in only a few i n d u s t r i a l p r o c e s s e s , i s e s s e n t i a l in n u c l e a r r e a c t o r s . Neut r o n s a r e a l s o p r o d u c e d t o g e t h e r with o t h e r t y p e s of r a d i a tion by high e n e r g y m a c h i n e s s u c h a s n e u t r o n g e n e r a t o r s , cyclotrons, linear accelerators,betatrons, synchrotrons or p r o t o n s y n c h r o t r o n s used, in the main, in r e s e a r c h e s t a b l i s h ments. HEALTH HAZARDS It h a s long b e e n r e c o g n i s e d t h a t ionizing r a d i a t i o n s c a n p r o duce h a r m f u l effects on the h u m a n body. Unlike many o t h e r hazardous substances, ionizing radiations give no immediate indication of their presence. The absorption of ionizing radiations by the body tissues produces no sensation and their harmful effects are normally delayed except in the case of very large doses. Ionizing radiations can be received by a person either from an external source outside the body or from radioactive material deposited internally within the body. Basically it is the radiation energy absorption by the atoms forming the body tissues and cells when they are ionized which can lead to effects on the skin, such as burns and radiological dermatitis, cataract formation in the-eyes and changes in the blood-forming organs with the possibility of leukaemia as a late effect. Furthermore there is the possibility of impaired fertility or sterility and there are possibi]/ties of excessive radiation producing deleterious genetic effects. It should not be overlooked that m a n y radioactive substances present toxicological as well as radiological hazards, particularly the longer-lived nuclides of uranium. It is important therefore that the hazard of chemical toxicity as w e U as that of radiotoxicity is taken into account when they are used.
CONTROL
OF RADIATION
HAZARDS
C u r r e n t l e g i s l a t i o n applying to p r e m i s e s s u b j e c t to the F a c t o r i e s A c t 1961 now i n c l u d e s two Codes of R e g u l a t i o n s . T h e I o n i s i n g R a d i a t i o n s (Sealed S o u r c e s ) R e g u l a t i o n s 1961 m a k e p r o v i s i o n s f o r the p r o t e c t i o n of w o r k e r s l i a b l e to be e x p o s e d to i o n i z i n g r a d i a t i o n s f r o m s e a l e d s o u r c e s of r a d i o a c t i v e s u b s t a n c e s and f r o m m a c h i n e s such a s x - r a y m a c h i n e s and p a r t i c l e a c c e l e r a t o r s . The Ionising R a d i a t i o n s ( U n s e a l e d R a d i o a c t i v e S u b s t a n c e s ) R e g u l a t i o n s 1968 w e r e m a d e i n May 1968, and they c o v e r t h e u s e of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s e i t h e r in the f o r m of solids, powder, liquid o r gas. n o n - d e s t r u c t i v e t e s t i n g August 1966
285
T h e s e r e g u l a t i o n s include r e q u i r e m e n t s a p p r o p r i a t e f o r the p r o c e s s of luminizing and when they b e c o m e law, the L u m i n i s i n g R e g u l a t i o n s 1947 will be revoked. The D e p a r t m e n t of E m p l o y m e n t and Productivity, in addition to its s t a t u t o r y i n t e r e s t u n d e r the F a c t o r i e s Act, i s involved in r a d i o l o g i c a l p r o t e c t i o n in n o n - i n d u s t r i a l e s t a b l i s h m e n t s , and a Code of P r a c t i c e f o r the p r o t e c t i o n of p e r s o n s e x p o s e d to ionizing r a d i a t i o n s in r e s e a r c h and teaching was i s s u e d in 1964 (originally i s s u e d by the M i n i s t r y of Labour). This Code a p p l i e s to a wide r a n g e of r e s e a r c h and t e a c h i n g in u n i v e r sities, medical schools, technical colleges, Government dep a r t m e n t s and i n d u s t r y g e n e r a l l y .
MAXIMUM
PERMISSIBLE
DOSES
The main purpose of the Regulations and Code of Practice is to ensure that persons working with ionizing radiations receive the smallest practicable dose and that no person receives a radiation dose in excess of the permitted levels of radiation. The m a x i m u m permissible doses specified in the Regulations and embodied in the Code of Practice are based on the recommendations of the International C o m m i s s i o n on Radiological Protection as endorsed by the Medical Research Council. In both Codes of Regulations and in the Code of Practice these doses only relate to ionizing radiations which originate in the factory or research establishment and do not take account of radiations used for diagnostic or therapeutic purposes. Briefly the m a x i m u m permissible dose permitted for persons engaged in work with ionizing radiations is an average of 5 r e m a year with not m o r e than 3rein in a calendar quarter. (The values of the doses to the critical organs and various parts of the body,based on the recommendations of I C B P 9 are set out in the Schedule in the recent Ionising Radiations (Unsealed Radioactive Substances) Regulations 1968. Appendix I on m a x i m u m permissible doses in the Code of Practice for the protection of persons exposed to Ionising Radiations in Research and Teaching is shortly to be amended. The revision of the Schedule in the Ionising Radiations (Sealed Sources) Regulations 1961 will follow later). F o r the p u r p o s e s of c o n t r o l of e x p o s u r e to ionizing r a d i a t i o n s in f a c t o r i e s , e m p l o y e e s a r e r e q u i r e d to b e d e s i g n a t e d a s ' c l a s s i f i e d w o r k e r s ' if they work on o p e r a t i o n s r e s u l t i n g in d o s e s which m i g h t e x c e e d 34 oths of the annual m a x i m u m p e r m i s s i b l e d o s e (i.e. 1 . 5 r e m ) . (The Code of P r a c t i c e u s e s the t e r m ' d e s i g n a t e d p e r s o n ' and o t h e r t e r m s for s i m i l a r c l a s s e s of p e r s o n a r e 'occupationally e x p o s e d p e r s o n ' and 'radiation worker'). Designation as ' c l a s s i f i e d w o r k e r s ' i s not r e q u i r e d if the working conditions and s y s t e m of c o n t r o l a r e such that a p e r s o n i s unlikely to r e c e i v e m o r e than 3hoths of the annual m a x i m u m p e r m i s s i b l e dose. By e x t r a p o l a t i o n of t h e s e s p e c i f i e d l i m i t s of 5 r e m and 1 . 5 r e i n , a s s u m i n g a 50 week y e a r and a 40 hour w e e k , t h e hourly d o s e r a t e s a r e 2.5 m i l l i r e m / h and 0.25 m i l l i r e m / h r e s p e c t i v e l y . The c o n c e p t of 'adequate s h i e l d i n g ' i s a b a s i c p r i n c i p l e in the R e g u l a t i o n s and in the Code of P r a c t i c e and i s b a s e d on t h e s e two l e v e l s . An 'adequately s h i e l d e d ' s o u r c e of ionizing r a d i a t i o n s m e a n s that it is p r o v i d e d with shielding o r a d e m a r c a t i n g b a r r i e r around it, in such a way that outside the shielding o r b a r r i e r , the r a d i a t i o n d o s e r a t e , a v e r a g e d o v e r any one minute, would not e x c e e d 0 . 7 5 m i l l i r e m / h or w h e r e only ' c l a s s i f i e d w o r k e r s ' a r e affected 2 . 5 m i l l i r e m / h
PRINCIPLES
3
D i s t a n c e f r o m the s o u r c e s
4
R e s t r i c t i o n of the p e r i o d of e x p o s u r e
One o r m o r e of t h e s e m e t h o d s should be u s e d to make s u r e that the d o s e s a r e kept below the m a x i m u m p e r m i s s i b l e l e v e l in any p a r t i c u l a r situation. The b e s t method of p r o t e c t i o n i s to a r r a n g e f o r the s o u r c e of ionizing r a d i a t i o n s to be 'adequately s h i e l d e d ' . E x c e p t i o n s a r e made for s e a l e d s o u r c e s of r a d i o a c t i v e m a t e r i a l and m a c h i n e s e m i t t i n g ic~izing r a d i a t i o n s with low radiation output w h e r e the h a z a r d is minimal.3,5
(a) X-radiography equipment X - r a d i o g r a p h y should be c a r r i e d out within a room o r walled e n c l o s u r e which p r o v i d e s 'adequate s h i e l d i n g ' . The shielding r e q u i r e m e n t s 6 for the w a l l s and d o o r s (and w h e r e n e c e s s a r y , a ceiling) will depend on the n a t u r e and s t r e n g t h of the s o u r c e u s e d and the r e q u i r e m e n t s of the work. The d o o r s of the x - r a d i o g r a p h y e n c l o s u r e should be i n t e r locked with the e l e c t r i c a l supply to the a p p a r a t u s in such a way that the x - r a y s cannot be g e n e r a t e d u n l e s s the d o o r s a r e c l o s e d and the a p p a r a t u s is d e - e n e r g i z e d if the door i s o p e n ed. S e v e r a l incidents have o c c u r r e d in i n d u s t r y owing to the f a i l u r e o r a b s e n c e of the i n t e r l o c k on the d o o r s of the e n c l o s u r e . It i s i m p o r t a n t t h e r e f o r e that the m e c h a n i c a l d e sign and method of o p e r a t i o n of i n t e r l o c k s 7 should be such that they cannot easily be b y p a s s e d o r r e n d e r e d inoperative. In o t h e r words, i n t e r l o c k s should 'fail s a f e ' ( F i g s 1 and 2). O t h e r r e q u i r e m e n t s a r e that the c o n t r o l panel should be outside the e n c l o s u r e , and, to avoid the r i s k of a p e r s o n b e ing a c c i d e n t a l l y shut i n s i d e the e n c l o s u r e , t h e r e should be a m e a n s of exit s o that he can leave without delay. It is also a d v i s a b l e to p r o v i d e m e a n s for switching off the a p p a r a t u s quickly inside the e n c l o s u r e in c a s e a p e r s o n is accidentally t r a p p e d inside.
_
Switch
I
I I
I
Y
,
a
OF PROTECTION
External radiation The b a s i c m e t h o d s of p r o t e c t i o n which can be u s e d to deal with e x t e r n a l r i s k s and which apply to the u s e of m a c h i n e s e m i t t i n g ionizing r a d i a t i o n s and s e a l e d s o u r c e s of r a d i o active s u b s t a n c e s a r e : 1
R e s t r i c t i o n of the s t r e n g t h of e v e r y s o u r c e
2
Shielding of s o u r c e s
286
n o n - d e s t r u c t i v e t e s t i n g August 1968
c
Fig. 1 Suitable arrangement f o r d o o r interlock. Mounting for positively interlocked switch for hinged door (based on an idea supplied by Pyrotenax Ltd)
W a r n i n g s i g n a l s should always be p r o v i d e d in the v i c i n i t y of x - r a y equipment s o that any one working in t h e a r e a i s a w a r e w h e t h e r o r not the equipment i s e n e r g i z e d . T h i s should b e by w a r n i n g l i g h t s o r audible s i g n a l s o r both, d e pending on c i r c u m s t a n c e s . The b e s t f o r m of w a r n i n g l i g h t i s an i n t e r n a l l y i l l u m i n a t e d sign with the w o r d s ' x - r a y s on' mounted at the e n t r a n c e of the e n c l o s u r e so that it can e a s i l y be s e e n f r o m any d i r e c t i o n . W h e n e v e r p o s s i b l e t h e s e w a r n ings should o p e r a t e a u t o m a t i c a l l y and be d e s i g n e d to fail s a f e . T h e r e may be i n s t a n c e s when it would be i m p r a c t i c a b l e or u n r e a s o n a b l e to c o n s t r u c t w a l l e d e n c l o s u r e s , a s for e x a m p l e when x - r a d i o g r a p h y e q u i p m e n t i s u s e d only v e r y o c c a s i o n a l l y , w h e r e l a r g e c a s t i n g s a r e difficult to m o v e , and when s i t e w o r k i s c o n c e r n e d . In such c i r c u m s t a n c e s d i s t a n c e p r o t e c tion would be r e q u i r e d (for p r e m i s e s u n d e r the F a c t o r i e s Act, s e e Regulation 33(1)(b) in Ref 3). The r a d i o g r a p h y equipment would need to be i s o l a t e d f r o m all o t h e r w o r k by m e a n s of a d e m a r c a t i n g b a r r i e r at s u c h a d i s t a n c e , and taking into account the t i m e in which the tube would be e n e r g i z e d , that 'adequate s h i e l d i n g ' would be p r o v i d e d for any p e r s o n outside the b a r r i e r . Suitable w a r n i n g n o t i c e s should b e a r r a n g e d at the b a r r i e r and the a r e a should be u n d e r s u p e r v i s i o n to e n s u r e no unauthorized e n t r y beyond the b a r r i e r .
(b) X-ray fluoroscopy equipment
(c) X-ray crystallography equipment P a r t i c u l a r c a r e is n e e d e d in the use of x - r a y c r y s t a l l o g r a p h y equipment b e c a u s e the v e r y high d o s e r a t e n e a r the t a r g e t a r e a can c a u s e injury in a v e r y s h o r t t i m e . The e q u i p m e n t should a l w a y s be o p e r a t e d so that it is ' a d e quately s h i e l d e d ' w h e n e v e r the tube i s e n e r g i z e d . To p r e v e n t f i n g e r s o r any o t h e r p a r t s of the body b e i n g ins e r t e d into the p r i m a r y b e a m each p o r t or a p e r t u r e of the x - r a y tube housing m u s t be p r o v i d e d with an automatic b e a m s h u t t e r s o a r r a n g e d that it can only be opened when the c o l l i mating s y s t e m is in p o s i t i o n . Since a p p r e c i a b l e s c a t t e r i n g of the useful x - r a y b e a m can occur, if it p a s s e s u n s h i e l d e d b e t w e e n the tube a p e r t u r e and the (first) c o l l i m a t o r of the a p p a r a t u s in u s e at the a p e r t u r e , t h i s p a r t of the useful b e a m should be c o m p l e t e l y e n c l o s e d to p r o v i d e adequate shielding ( s e e Regulation 37 in Ref 3). A l a b y r i n t h p a t t e r n , made of coupling, is usually the b e s t method. P r e c a u t i o n s m u s t a l s o b e taken to p r e v e n t e x p o s u r e , p a r t i c u l a r l y to f i n g e r s and hands and e y e s , during a l i g n m e n t . It should be e n s u r e d that all p e r s o n s in the vicinity a r e w a r ned that the equipment i s about to be e n e r g i z e d , and when it is energized.
(d) Sealed sources of radioactive substances
S i m i l a r p r e c a u t i o n s a r e r e q u i r e d when x - r a y s a r e u s e d for f l u o r o s c o p y . The e n c l o s u r e p r o v i d i n g 'adequate s h i e l d i n g ' is usually in the f o r m of a cabinet with i n t e r l o c k e d a c c e s s p a n e l s . The d e s i g n of the equipment should e n s u r e that the useful b e a m cannot fall o u t s i d e the s c r e e n and when r e a s o n ably p r a c t i c a b l e , the s c r e e n should be viewed i n d i r e c t l y o r by i m a g e i n t e n s i f i c a t i o n . It should be e m p h a s i z e d that all m a c h i n e s o r a p p a r a t u s e m i t t i n g ionizing r a d i a t i o n s should be thoroughly c h e c k e d a f t e r any a l t e r a t i o n o r t r a n s f e r to a n o t h e r s i t e . F o r e x a m p l e the o m i s s i o n to check that the viewing s c r e e n is in p o s i t i o n in x - r a y f l u o r e s c e n t equipment can and has r e s u l t e d in o v e r - e x p o s u r e of the o p e r a t o r .
When r a d i o a c t i v e s u b s t a n c e s in the f o r m of s e a l e d s o u r c e s a r e u s e d , the p r e c a u t i o n s a r e in many r e s p e c t s s i m i l a r to t h o s e r e q u i r e d for x - r a y equipment. The s a m e b a s i c p r i n c i p l e s of p r o t e c t i o n should be applied. The b e s t a r r a n g e m e n t for the p o w e r f u l g a m m a - e m i t t i n g s o u r c e s u s e d for g a m m a r a d i o g r a p h y is to p r o v i d e a s e p a r a t e r o o m , for which the amount of shielding and d i s t a n c e p r o t e c t i o n p r o v i d e d should c o n s t i t u t e 'adequate shielding.' F a c i l i t i e s for r e m o t e handling o r r e m o t e control of s e a l e d s o u r c e s of r a d i o a c t i v e m a t e r i a l should always be p r o v i d e d . All m a n i p u l a t i o n s should be c o m p l e t e d b e f o r e the s o u r c e is e x p o s e d . T r i a l r u n s , using a d u m m y s o u r c e , without exposing the s o u r c e o r e n e r g i z i n g the x - r a y machine a r e d e s i r a b l e for all r a d i o g r a p h i c w o r k . P e r s o n s a u t h o r i z e d to c a r r y out g a m m a r a d i o g r a p h y should 0rdy have a c c e s s to the a r e a f o r the m i n i m u m t i m e and only under conditions which e n s u r e they a r e adequately p r o t e c t e d . When a s e a l e d s o u r c e of r a d i o a c t i v e s u b s t a n c e s is u s e d in a static e l i m i n a t o r , t h i c k n e s s gauge o r s i m i l a r device, it m u s t not only b e 'adequately s h i e l d e d ; but be p r o v i d e d with a s u i table c o v e r plate o r s h u t t e r so that the useful b e a m i s a t t e nuated, so f a r a s i s r e a s o n a b l y p r a c t i c a b l e , when not in u s e .
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B e c a u s e of the p o s s i b i l i t i e s of d a m a g e to s e a l e d s o u r c e s t h e r e a r e r e q u i r e m e n t s a s to action to be taken In the event of leakage o r b r e a k a g e . They should be t e s t e d for leakage and consequent s u r f a c e contamination by a qualified e x p e r t , at l e a s t o n c e in e v e r y 26 m o n t h s , o r i m m e d i a t e l y if a leak is suspected.
Internal radiation
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Special h a z a r d s a r e a s s o c i a t e d with the u s e of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s b e c a u s e p r e c a u t i o n s have to be taken a g a i n s t the r i s k s of i n t e r n a l r a d i a t i o n a s w e l l a s e x t e r n a l radiation. The r e q u i r e m e n t s depend on the s t r e n g t h of the s o u r c e s involved, the r a d i o t o x i c i t y , c h e m i c a l toxicity and o t h e r c h e m i cal and p h y s i c a l p r o p e r t i e s a s well a s the nature of the o p e r a t i o n s . T h e r e a r e again l o w e r l i m i t s of activity below which the R e g u l a t i o n s and Code of P r a c t i c e do not apply. The b a s i c m e t h o d s of p r o t e c t i o n which n e e d to be taken to m i n i m i z e the d e p o s i t i o n within the body of r a d i o a c t i v e subr s t a n c e s , w h e t h e r by inhalation, ingestion o r o t h e r m e a n s are." 1
Fig. 2 Mounting f o r p o s i t i v e l y i n t e r l o c k e d switch f o r sliding door
The u s e of m a t e r i a l of m i n i m u m radtotoxicity
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P r o t e c t i o n against i n t e r n a l r a d i a t i o n i s b e s t a c h i e v e d by s e p a r a t i o n and containment of all o p e r a t i o n s with u n s e a l e d r a d i o a c t i v e s u b s t a n c e s . The a r e a s d e s i g n a t e d for such work should be c l e a r l y m a r k e d (see Regulation 2 in Ref 4 and p a r a g r a p h 9 . 2 . 1 in Ref 5).
When p r o t e c t i v e clothing is provided, suitable a c c o m m o d a t i o n for changing and s t o r a g e should be available. Special a r r a n g e m e n t s will need to be made for cleaning o r washing p r o t e c tive clothing c o n t a m i n a t e d above the m a x i m u m p e r m i s s i b l e l e v e l s for s u r f a c e contamination.4, 5
The m o s t effective way of providing c o n t a i n m e n t and l i m i t i n g the s p r e a d of contamination is to a r r a n g e for the w o r k to be c a r r i e d out in a total e n c l o s u r e . T h i s should be in the f o r m of a glove box for handling the m o s t toxic r a d i o a c t i v e m a t e r i a l s (i.e. C l a s s I in the c l a s s i f i c a t i o n of Radionuclides), a n d / o r r a d i o a c t i v e m a t e r i a l in p a r t i c u l a r f o r m . In o t h e r c a s e s an efficient fume cupboard may p r o v i d e a sufficient f o r m of e n c l o s u r e . Both total e n c l o s u r e s and fume c u p b o a r d s m u s t have m e c h a n i c a l exhaust e x t r a c t i o n to p r e v e n t the e s c a p e of a i r b o r n e r a d i o a c t i v e m a t e r i a l into the w o r k r o o m or laboratory.
E a s i l y a c c e s s i b l e washing f a c i l i t i e s should be p r o v i d e d and s t a n d a r d s a r e laid down a s to design and n u m b e r of w a s h b a s i n s a c c o r d i n g to the n u m b e r of p e r s o n s c o n c e r n e d . Hands should be w a s h e d and checked for contamination b e f o r e l e a v ing the a r e a .
(a) Design and equipment T h e r e a r e r e q u i r e m e n t s about the d e s i g n and type of equipm e n t that should be u s e d for e x p e r i m e n t a l work in f a c t o r y p r o c e s s e s , in p r o c e s s c o n t r o l l a b o r a t o r i e s o r in r e s e a r c h e s t a b l i s h m e n t s . F l o o r s , w a l l s , c e i l i n g s and b e n c h tops should have s m o o t h i m p e r v i o u s s u r f a c e s which can be e a s i l y c l e a n e d and d e c o n t a m i n a t e d . A trouble spot for contamination can b e found in gaps in floor c o v e r i n g s , so joints should be e f f e c t i v e ly s e a l e d , and ledges and i n a c c e s s i b l e p l a c e s liable to c o l l e c t dust should be e l i m i n a t e d a s f a r a s p o s s i b l e . The layout of equipment will v a r y a c c o r d i n g to c i r c u m s t a n c e s and only e s s e n t i a l f u r n i t u r e and fittings should be allowed. C a r e should be taken to e n s u r e e a s y a c c e s s to adequate m e a n s of e s c a p e in the event of f i r e or o t h e r e m e r g e n c y such a s s p i l l s o r e s c a p e of r a d i o a c t i v e m a t e r i a l s .
(b) Methods of work Methods of w o r k with u n s e a l e d r a d i o a c t i v e s u b s t a n c e s have to be such a s to avoid s p i l l s o r c r e a t i n g d u s t . A p p a r a t u s and equipment u s e d for t h i s work should not be u s e d for o t h e r p u r p o s e s u n l e s s it has b e e n checked f o r contamination. The mouth must not c o m e into contact with any apparatus; for example, p i p e t t e s must be o p e r a t e d by o t h e r m e a n s . B r u s h e s m u s t not be u s e d for the application of luminizing compounds, but if u s e d for the a p p l i c a t i o n o f o t h e r r a d i o a c t i v e s u b s t a n c e s the o p e r a t i o n m u s t only be c a r r i e d out in a total e n c l o s u r e . The s t a n d a r d of c l e a n l i n e s s m u s t be v e r y high in a r e a s u s e d for work with r a d i o a c t i v e s u b s t a n c e s and routine cleaning, by m e t h o d s which avoid s p r e a d of contamination, should be c a r r i e d out at frequent i n t e r v a l s to p r e v e n t r e s i d u a l c o n t a m i nation f r o m exceeding the p e r m i t t e d l e v e l s (see Schedule 2 in Ref 4 and Appendix 2 in Ref 5). M a t e r i a l s and equipment u s e d for cleaning should not be u s e d outside t h e s e a r e a s , o t h e r w i s e t h e r e is r i s k of s p r e a d of contamination.
(c) Personal hygiene T h e r e a r e s p e c i a l r e q u i r e m e n t s a s to p e r s o n a l hygiene to p r e v e n t ingestion, inhalation o r o t h e r a b s o r p t i o n of r a d i o a c tive m a t e r i a l . Eating, drinking, smoking, taking of snuff and the application of c o s m e t i c s m u s t obviously not take p l a c e in a r e a s subject to c o n t r o l . O r d i n a r y h a n d k e r c h i e v e s should not be used; p a p e r h a n d k e r c h t e v e s should b e p r o v i d e d and used, and a f t e r u s e should be d i s p o s e d of a s r a d i o a c t i v e w a s t e . T h e r e a r e a l s o r e q u i r e m e n t s for p r o t e c t i o n of cuts or b r e a k s in the skin which must b e c h e c k e d a s to d r e s s i n g s and c o v e r ings and if contamination i s p r e s e n t the f a c t s m u s t be r e p o r t e d a s soon a s p o s s i b l e for i n v e s t i g a t i o n and m e d i c a l s u r v e i l l a n c e if n e c e s s a r y .
Storage and t r a n s p o r t within p r e m i s e s Another i m p o r t a n t a s p e c t of p r o t e c t i o n is that a r r a n g e m e n t s must be made f o r all s o u r c e s , both s e a l e d and unsealed, to be s e c u r e l y s t o r e d when not in use. The s t o r e should be 'adequately s h i e l d e d ' and if r a d i o a c t i v e gas, dust or vapour i s liable to be p r e s e n t , the s t o r e will need to be efficiently ventilated by m e c h a n i c a l m e a n s . The s t o r e should be so c o n s t r u c t e d a s to m i n i m i z e the r i s k f r o m f i r e and should be in the c h a r g e of a r e s p o n s i b l e p e r s o n . The b a s i c p r i n c i p l e s of p r o t e c t i o n should be applied when r a d i o a c t i v e s u b s t a n c e s a r e t r a n s p o r t e d within the f a c t o r y or r e s e a r c h e s t a b l i s h m e n t . C o n t a i n e r s should p r o v i d e ' a d e quate s h i e l d i n g ' and c o n t a i n e r s used f o r u n s e a l e d r a d i o a c t i v e s u b s t a n c e s should be d e s i g n e d and c o n s t r u c t e d so a s to p r e vent the s p r e a d of contamination or d i s p e r s a l of g a s e o u s radioactive substances. U p - t o - d a t e r e c o r d s should be kept of all r a d i o a c t i v e subs t a n c e s and in the c a s e of u n s e a l e d s o u r c e s , w h e r e a p p r o p r i a t e , the date and m a n n e r of t h e i r subsequent d i s p o s a l . If the accounting s y s t e m s h o w s that a s o u r c e has b e e n lost or m i s l a i d , the p e r s o n in c h a r g e m u s t be notified without delay so that p r o m p t action can be taken for i t s r e c o v e r y . All p r o t e c t i v e c o n t a i n e r s u s e d for r a d i o a c t i v e s o u r c e s should be c l e a r l y l a b e l l e d by a distinguishing n u m b e r o r identifying m a r k to avoid e r r o r s and p o s s i b l e r i s k of e x c e s s i v e r a d i a tion when s o u r c e s a r e i s s u e d f r o m the s t o r e . Radiological and m e d i c a l s u p e r v i s i o n P e r s o n s who a r e d e s i g n a t e d a s ' c l a s s i f i e d w o r k e r s ' can only be p e r m i t t e d to work in conditions w h e r e they a r e likely to r e c e i v e m o r e than t h r e e t e n t h s of the annual m a x i m u m p e r m i s s i b l e d o s e s if they a r e subject to p e r s o n a l m o n i t o r i n g and m e d i c a l s u p e r v i s i o n . In c u r r e n t l e g i s l a t i o n and the Code of P r a c t i c e the method r e q u i r e d for p e r s o n a l m o n i t o r i n g is t h e w e a r i n g of a suitable photographic f i l m in an a p p r o p r i a t e holder o r o t h e r suitable d o s e m e t e r . The f i l m badge should be obtained f r o m an a p p r o v e d l a b o r a t o r y such a s the Radiological P r o t e c t i o n S e r v i c e * and they should be r e t u r n e d for examination a f t e r being w o r n . It will be a d v i s a b l e to a r r a n g e for b i o l o g i c a l m o n i t o r i n g (evaluation of a m o u n t s of r a d i o a c t i v e s u b s t a n c e s in the body by m e a s u r e m e n t of the a m o u n t s being e x c r e t e d or. o t h e r a p p r o p r i a t e m e a n s ) , w h e r e significant a m o u n t s of m o r e h a z a r d o u s m a t e r i a l s such a s plutonium, radium, s t r o n t i u m , polonium, c a e s i u m or r a d i o - i o d i n e a r e u s e d . Biological m o n i t o r i n g is the only f e a s i b l e m e t h o d f o r t e s t i n g for p e r s o n a l e x p o s u r e to the weak b e t a e m i t t e r s such a s t r i t i u m , c a r b o n 14 and sulphur 35. Radiation r e c o r d s a r e r e q u i r e d to be kept to p r o v i d e a c o n tinuous check on the extent of d o s e s r e c e i v e d . ' C l a s s i f i e d w o r k e r s ' should r e c e i v e p e r i o d i c m e d i c a l e x a m i nations so long a s they continue to be e n g a g e d in t h i s work. To p r e v e n t the e m p l o y m e n t of p e r s o n s not fit f o r t h i s work initial m e d i c a l e x a m i n a t i o n s a r e a l s o r e q u i r e d . R e c o r d s of t h e s e e x a m i n a t i o n s a r e e s s e n t i a l to enable the health of the p e r s o n s c o n c e r n e d to be kept under c o n s t a n t r e v i e w .
(d) Protective equipment Ideally, the f i r s t line of p r o t e c t i o n is to s a f e g u a r d the s o u r c e , but w h e r e u n s e a l e d r a d i o a c t i v e s u b s t a n c e s a r e u s e d , p r o t e c tive equipment is r e q u i r e d to p r e v e n t the p o s s i b i l i t y of c o n t a m i n a t i o n of skin, hair and p e r s o n a l clothing. F o r c e r t a i n o p e r a t i o n s , b r e a t h i n g a p p a r a t u s should be available, p a r t i c u l a r l y w h e r e t h e r e i s liable to be a h a z a r d f r o m g a s e o u s or a i r b o r n e r a d i o a c t i v e m a t e r i a l . T h e r e a r e r e q u i r e m e n t s for the b r e a t h i n g apparatus to be e x a m i n e d and t e s t e d .
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Monitoring of the working environment The e f f e c t i v e n e s s of p r o t e c t i v e m e a s u r e s must be a s s e s s e d by r e g u l a r m o n i t o r i n g of the working e n v i r o n m e n t , to check the l e v e l s of e x t e r n a l r a d i a t i o n and the amount of c o n t a m i n a tion on s u r f a c e s . A p p r o p r i a t e m o n i t o r i n g i n s t r u m e n t s m u s t
* Clifton Avenue,Belmont,Sutton,Surrey, England
t h e r e f o r e be p r o v i d e d and they should b e t e s t e d and calibrated when f i r s t t a k e n into u s e a n d r e - t e s t e d and r e - c a l i b r a t e d p e r i o d i c a l l y (at l e a s t once in e v e r y 14 m o n t h s in factory premises).
REFERENCES I n t e r n a t i o n a l C o m m i s s i o n on R a d i o l o g i c a l P r o t e c t i o n I C R P P u b l i c a t i o n 2. R e p o r t of C o m m i t t e e H on P e r m i s s i b l e Dose for I n t e r n a l Radiation, 1959. P e r g a m o n P r e s s
S u p e r v i s i o n a n d tr~inlru~ T h e p r i m a r y r e s p o n s i b i l i t y f o r o b s e r v a n c e of t h e l e g a l r e q u i r e m e n t s and r e c o m m e n d a t i o n s of t h e Code of P r a c t i c e r e s t s with the f a c t o r y o c c u p i e r o r t h e c o n t r o l l i n g a u t h o r i t y of t h e r e s e a r c h e s t a b l i s h m e n t . An a d m i n i s t r a t i v e o r g a n i z a tion should be s e t up to m a t c h the extent a n d c h a r a c t e r of these responsibilities. P e r s o n s a p p o i n t e d to e x e r c i s e s u p e r v i s i o n and to a s s i s t with the r e q u i r e m e n t s for r a d i o l o g i c a l s a f e t y should be c o m p e tent to d e a l w i t h the n a t u r e of the work a n d the r i s k s i n v o l v e d and e x e r c i s e s u r v e i l l a n c e of a l l e q u i p m e n t and p l a n t . All p e r s o n s l i a b l e to b e e x p o s e d to ionizing r a d i a t i o n s a r e r e q u i r e d to be i n s t r u c t e d about the h a z a r d s i n v o l v e d in t h e w o r k a n d about the p r e c a u t i o n s to b e o b s e r v e d . T h e extent of t h e i n s t r u c t i o n will depend on the n a t u r e of t h e w o r k and a p p r o p r i a t e c o u r s e s of i n s t r u c t i o n s a r r a n g e d w h e r e n e c e s s a r y .
ICRP P u b l i c a t i o n 9. R e c o m m e n d a t i o n s of the I n t e r n a t i o n a l C o m m i s s i o n on R a d i o l o g i c a l P r o t e c t i o n . Pergamon Press 3
T h e I o n i s i n g R a d i a t i o n s (Sealed S o u r c e s ) R e g u l a t i o n s 1961 (SI 1961 No 1470). H e r M a j e s t y ' s S t a t i o n e r y Office
4
T h e Ionising R a d i a t i o n s ( U n s e a l e d R a d i o a c t i v e Subs t a n c e s ) R e g u l a t i o n s 1968 (SI 1968 No 780). HMSO
5
Code of P r a c t i c e for the p r o t e c t i o n of p e r s o n s exposed to Ionising R a d i a t i o n s in R e s e a r c h a n d T e a c h i n g . HMSO 'A handbook of d a t a for r a d i o l o g i c a l p r o t e c t i o n ' , p r e p a r e d by a p a n e l of the R a d i o a c t i v e S u b s t a n c e s A d v i s o r y C o m m i t t e e (to b e p u b l i s h e d s h o r t l y )
ACKNOWLEDGEMENTS T h e a u t h o r w i s h e s to t h a n k H M Chief I n s p e c t o r of F a c t o r i e s , M r W. J . C. P l u m b e , b y w h o s e p e r m i s s i o n t h i s a r t i c l e i s published.
7
' E l e c t r i c a l l i m i t s w i t c h e s and t h e i r application', Safety, Health and W e l f a r e P a m p h l e t , New s e r i e s No 24. HMSO
n o n - d e s t r u c t i v e t e s t i n g August 1968
289
T h i s a r t i c l e s u m m a r i z e s the m a i n p r e c a u t i o n s and c o n t r o l s f o r the m o r e c o m m o n u s e s of ionizing r a d i a t i o n s . The m a i n a i m of t h e l e g a l r e q u i r e m e n t s and r e c o m m e n d a t i o n s of the Code of P r a c t i c e i s to e n s u r e t h a t p e r s o n s working with ionizing r a d i a t i o n s do not r e c e i v e a dose of r a d i a t i o n in e x c e s s of t h e m a x i m u m p e r m i s s i b l e doses. All u s e r s should be fully a w a r e of t h e s e r e q u i r e m e n t s a n d if n e c e s s a r y s e e k e x p e r t a d v i c e b e f o r e u n d e r t a k i n g work with ionizing r a d i a tions.
During r e c e n t y e a r s t h e r e h a s b e e n a r e m a r k a b l e i n c r e a s e in the u s e of r a d i o i s o t o p e s and x - r a y equipment, and ionizing r a d i a t i o n s a r e now a v a l u a b l e tool in i n d u s t r y a n d r e s e a r c h and a r e b e i n g u s e d to e x a m i n e and i m p r o v e t h e quality of a v a r i e t y of p r o d u c t s and to obtain new knowledge about the m e c h a n i s m of c h e m i c a l , e n g i n e e r i n g and biological p r o c e s s e s . It i s h o w e v e r e s s e n t i a l that all u s e r s should b e a w a r e of t h e p o t e n t i a l h a z a r d s to h e a l t h t h a t can a r i s e f r o m t h e i r u s e if p r o p e r p r e c a u t i o n s a r e not taken. It is i m p o r t a n t t h a t t h e r e s h o u l d b e effective s u p e r v i s i o n to c o u n t e r r i s k s in t h e i r u s e a n d t h a t a r r a n g e m e n t s b e m a d e to keep in step with national legislation and international recommendations. MAIN USES X - r a y s have b e e n used for x - r a d i o g r a p h y for many y e a r s . Today, x - r a y s and )~-rays f r o m such i s o t o p e s a s cobalt 60, c a e s i u m 137 and i r i d i u m 192 a r e p r o b a b l y a m o n g the m o s t c o m m o n l y u s e d ionizing r a d i a t i o n s in i n d u s t r y f o r x and 7 r a d i o g r a p h i c e x a m i n a t i o n s of m e t a l c a s t i n g s , welds and f a b r i c a t e d m e t a l c o m p o n e n t s . X - r a y s a r e a l s o u s e d in i n d u s t r y f o r t h e f l u o r o s c o p i c e x a m i n a t i o n of v a r i o u s m a n u factured articles for checking correct assembly or detecting f o r e i g n m a t t e r . X - r a y c r y s t a l l o g r a p h y equipment, f o r such p u r p o s e s a s the a n a l y s i s of c r y s t a l l i n e s u b s t a n c e s , i s used to a l e s s e r extent in f a c t o r i e s , but h a s a wide application in r e s e a r c h . It s h o u l d not b e f o r g o t t e n t h a t c e r t a i n a p p a r a t u s u s e d in both i n d u s t r y and r e s e a r c h a l s o e m i t s ionizing r a d i a tions, a s in the c a s e of e l e c t r o n m i c r o s c o p e s , high power t r a n s m i t t i n g a n d r e c t i f y i n g v a l v e s , i m a g e i n t e n s i f i e r s and c e r t a i n cathode r a y tubes. In addition to the u s e of r a d i o i s o t o p e s f o r ),-radiography, the r a d i a t i o n s f r o m v a r i o u s i s o t o p e s a r e e m p l o y e d in a v a r i e t y of i n s t r u m e n t s a n d m e a s u r i n g d e v i c e s , s u c h a s t h i c k n e s s gauges, l e v e l gauges, package m o n i t o r s , s t a t i c e l i m i n a t o r s and c h r o m a t o g r a p h s . T h i c k n e s s gauges, f o r e x a m p l e , a r e u s e d in I n d u s t r y f o r m e a s u r i n g and c o n t r o l l i n g the t h i c k n e s s of m a t e r i a l s such a s sheet metal, plastic and paper. L e v e l gauges s i m i l a r l y employ r a d i o i s o t o p e s for m e a s u r i n g and c o n t r o l l i n g t h e l e v e l of c o n t e n t s in e n c l o s e d v e s s e l s . On the o t h e r hand, s t a t i c e l i m i n a t o r s a r e u s e d to d i s c h a r g e un o wanted s t a t i c e l e c t r i c i t y which a r i s e s in i n d u s t r i a l p r o c e s s e s s u c h a s p a p e r m a k i n g and in the m a n u f a c t u r e of textiles. The r a d i o i s o t o p e s u s e d for the p u r p o s e s a l r e a d y i n d i c a t e d a r e in the f o r m of what a r e known a s s e a l e d s o u r c e s . T h e r e a r e a l s o i m p o r t a n t u s e s of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s f o r e x p e r i m e n t a l work in f a c t o r y p r o c e s s e s and in r e s e a r c h projects.
* A d v i s o r y and I n f o r m a t i o n Unit, D e p a r t m e n t of E m p l o y m e n t and P r o d u c t i v i t y , B a y n a r d s House, 1-13 Chepstow P l a c e , W e s t b o u r n e G r o v e , Londc~ W2, England
A long known u s e of u n s e a l e d r a d i o a c t i v e s o u r c e s in i n d u s t r y i s in t h e p r o c e s s of l u m i n i z i n g . T h e r e a r e a l s o a few f a c t o r i e s in which o r e s a r e p r o c e s s e d f r o m which r a d i o a c t i v e m a t e r i a l s a r e p r e p a r e d in s u i t a b l e f o r m s f o r u s e in i n d u s t r y , and p a r t i c u l a r l y v a r i o u s a s p e c t s of r e s e a r c h . T h e r e a r e d i f f e r e n t t y p e s of i o n i z i n g r a d i a t i o n s with d i f f e r ing p r o p e r t i e s ; the ones m o s t c o m m o n l y u s e d a r e x a n d g a m m a r a y s , a n d a l p h a and b e t a p a r t i c l e s . A n o t h e r type of i o n i z i n g r a d i a t i o n , n e u t r o n s , although u s e d in only a few i n d u s t r i a l p r o c e s s e s , i s e s s e n t i a l in n u c l e a r r e a c t o r s . Neut r o n s a r e a l s o p r o d u c e d t o g e t h e r with o t h e r t y p e s of r a d i a tion by high e n e r g y m a c h i n e s s u c h a s n e u t r o n g e n e r a t o r s , cyclotrons, linear accelerators,betatrons, synchrotrons or p r o t o n s y n c h r o t r o n s used, in the main, in r e s e a r c h e s t a b l i s h ments. HEALTH HAZARDS It h a s long b e e n r e c o g n i s e d t h a t ionizing r a d i a t i o n s c a n p r o duce h a r m f u l effects on the h u m a n body. Unlike many o t h e r hazardous substances, ionizing radiations give no immediate indication of their presence. The absorption of ionizing radiations by the body tissues produces no sensation and their harmful effects are normally delayed except in the case of very large doses. Ionizing radiations can be received by a person either from an external source outside the body or from radioactive material deposited internally within the body. Basically it is the radiation energy absorption by the atoms forming the body tissues and cells when they are ionized which can lead to effects on the skin, such as burns and radiological dermatitis, cataract formation in the-eyes and changes in the blood-forming organs with the possibility of leukaemia as a late effect. Furthermore there is the possibility of impaired fertility or sterility and there are possibi]/ties of excessive radiation producing deleterious genetic effects. It should not be overlooked that m a n y radioactive substances present toxicological as well as radiological hazards, particularly the longer-lived nuclides of uranium. It is important therefore that the hazard of chemical toxicity as w e U as that of radiotoxicity is taken into account when they are used.
CONTROL
OF RADIATION
HAZARDS
C u r r e n t l e g i s l a t i o n applying to p r e m i s e s s u b j e c t to the F a c t o r i e s A c t 1961 now i n c l u d e s two Codes of R e g u l a t i o n s . T h e I o n i s i n g R a d i a t i o n s (Sealed S o u r c e s ) R e g u l a t i o n s 1961 m a k e p r o v i s i o n s f o r the p r o t e c t i o n of w o r k e r s l i a b l e to be e x p o s e d to i o n i z i n g r a d i a t i o n s f r o m s e a l e d s o u r c e s of r a d i o a c t i v e s u b s t a n c e s and f r o m m a c h i n e s such a s x - r a y m a c h i n e s and p a r t i c l e a c c e l e r a t o r s . The Ionising R a d i a t i o n s ( U n s e a l e d R a d i o a c t i v e S u b s t a n c e s ) R e g u l a t i o n s 1968 w e r e m a d e i n May 1968, and they c o v e r t h e u s e of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s e i t h e r in the f o r m of solids, powder, liquid o r gas. n o n - d e s t r u c t i v e t e s t i n g August 1966
285
T h e s e r e g u l a t i o n s include r e q u i r e m e n t s a p p r o p r i a t e f o r the p r o c e s s of luminizing and when they b e c o m e law, the L u m i n i s i n g R e g u l a t i o n s 1947 will be revoked. The D e p a r t m e n t of E m p l o y m e n t and Productivity, in addition to its s t a t u t o r y i n t e r e s t u n d e r the F a c t o r i e s Act, i s involved in r a d i o l o g i c a l p r o t e c t i o n in n o n - i n d u s t r i a l e s t a b l i s h m e n t s , and a Code of P r a c t i c e f o r the p r o t e c t i o n of p e r s o n s e x p o s e d to ionizing r a d i a t i o n s in r e s e a r c h and teaching was i s s u e d in 1964 (originally i s s u e d by the M i n i s t r y of Labour). This Code a p p l i e s to a wide r a n g e of r e s e a r c h and t e a c h i n g in u n i v e r sities, medical schools, technical colleges, Government dep a r t m e n t s and i n d u s t r y g e n e r a l l y .
MAXIMUM
PERMISSIBLE
DOSES
The main purpose of the Regulations and Code of Practice is to ensure that persons working with ionizing radiations receive the smallest practicable dose and that no person receives a radiation dose in excess of the permitted levels of radiation. The m a x i m u m permissible doses specified in the Regulations and embodied in the Code of Practice are based on the recommendations of the International C o m m i s s i o n on Radiological Protection as endorsed by the Medical Research Council. In both Codes of Regulations and in the Code of Practice these doses only relate to ionizing radiations which originate in the factory or research establishment and do not take account of radiations used for diagnostic or therapeutic purposes. Briefly the m a x i m u m permissible dose permitted for persons engaged in work with ionizing radiations is an average of 5 r e m a year with not m o r e than 3rein in a calendar quarter. (The values of the doses to the critical organs and various parts of the body,based on the recommendations of I C B P 9 are set out in the Schedule in the recent Ionising Radiations (Unsealed Radioactive Substances) Regulations 1968. Appendix I on m a x i m u m permissible doses in the Code of Practice for the protection of persons exposed to Ionising Radiations in Research and Teaching is shortly to be amended. The revision of the Schedule in the Ionising Radiations (Sealed Sources) Regulations 1961 will follow later). F o r the p u r p o s e s of c o n t r o l of e x p o s u r e to ionizing r a d i a t i o n s in f a c t o r i e s , e m p l o y e e s a r e r e q u i r e d to b e d e s i g n a t e d a s ' c l a s s i f i e d w o r k e r s ' if they work on o p e r a t i o n s r e s u l t i n g in d o s e s which m i g h t e x c e e d 34 oths of the annual m a x i m u m p e r m i s s i b l e d o s e (i.e. 1 . 5 r e m ) . (The Code of P r a c t i c e u s e s the t e r m ' d e s i g n a t e d p e r s o n ' and o t h e r t e r m s for s i m i l a r c l a s s e s of p e r s o n a r e 'occupationally e x p o s e d p e r s o n ' and 'radiation worker'). Designation as ' c l a s s i f i e d w o r k e r s ' i s not r e q u i r e d if the working conditions and s y s t e m of c o n t r o l a r e such that a p e r s o n i s unlikely to r e c e i v e m o r e than 3hoths of the annual m a x i m u m p e r m i s s i b l e dose. By e x t r a p o l a t i o n of t h e s e s p e c i f i e d l i m i t s of 5 r e m and 1 . 5 r e i n , a s s u m i n g a 50 week y e a r and a 40 hour w e e k , t h e hourly d o s e r a t e s a r e 2.5 m i l l i r e m / h and 0.25 m i l l i r e m / h r e s p e c t i v e l y . The c o n c e p t of 'adequate s h i e l d i n g ' i s a b a s i c p r i n c i p l e in the R e g u l a t i o n s and in the Code of P r a c t i c e and i s b a s e d on t h e s e two l e v e l s . An 'adequately s h i e l d e d ' s o u r c e of ionizing r a d i a t i o n s m e a n s that it is p r o v i d e d with shielding o r a d e m a r c a t i n g b a r r i e r around it, in such a way that outside the shielding o r b a r r i e r , the r a d i a t i o n d o s e r a t e , a v e r a g e d o v e r any one minute, would not e x c e e d 0 . 7 5 m i l l i r e m / h or w h e r e only ' c l a s s i f i e d w o r k e r s ' a r e affected 2 . 5 m i l l i r e m / h
PRINCIPLES
3
D i s t a n c e f r o m the s o u r c e s
4
R e s t r i c t i o n of the p e r i o d of e x p o s u r e
One o r m o r e of t h e s e m e t h o d s should be u s e d to make s u r e that the d o s e s a r e kept below the m a x i m u m p e r m i s s i b l e l e v e l in any p a r t i c u l a r situation. The b e s t method of p r o t e c t i o n i s to a r r a n g e f o r the s o u r c e of ionizing r a d i a t i o n s to be 'adequately s h i e l d e d ' . E x c e p t i o n s a r e made for s e a l e d s o u r c e s of r a d i o a c t i v e m a t e r i a l and m a c h i n e s e m i t t i n g ic~izing r a d i a t i o n s with low radiation output w h e r e the h a z a r d is minimal.3,5
(a) X-radiography equipment X - r a d i o g r a p h y should be c a r r i e d out within a room o r walled e n c l o s u r e which p r o v i d e s 'adequate s h i e l d i n g ' . The shielding r e q u i r e m e n t s 6 for the w a l l s and d o o r s (and w h e r e n e c e s s a r y , a ceiling) will depend on the n a t u r e and s t r e n g t h of the s o u r c e u s e d and the r e q u i r e m e n t s of the work. The d o o r s of the x - r a d i o g r a p h y e n c l o s u r e should be i n t e r locked with the e l e c t r i c a l supply to the a p p a r a t u s in such a way that the x - r a y s cannot be g e n e r a t e d u n l e s s the d o o r s a r e c l o s e d and the a p p a r a t u s is d e - e n e r g i z e d if the door i s o p e n ed. S e v e r a l incidents have o c c u r r e d in i n d u s t r y owing to the f a i l u r e o r a b s e n c e of the i n t e r l o c k on the d o o r s of the e n c l o s u r e . It i s i m p o r t a n t t h e r e f o r e that the m e c h a n i c a l d e sign and method of o p e r a t i o n of i n t e r l o c k s 7 should be such that they cannot easily be b y p a s s e d o r r e n d e r e d inoperative. In o t h e r words, i n t e r l o c k s should 'fail s a f e ' ( F i g s 1 and 2). O t h e r r e q u i r e m e n t s a r e that the c o n t r o l panel should be outside the e n c l o s u r e , and, to avoid the r i s k of a p e r s o n b e ing a c c i d e n t a l l y shut i n s i d e the e n c l o s u r e , t h e r e should be a m e a n s of exit s o that he can leave without delay. It is also a d v i s a b l e to p r o v i d e m e a n s for switching off the a p p a r a t u s quickly inside the e n c l o s u r e in c a s e a p e r s o n is accidentally t r a p p e d inside.
_
Switch
I
I I
I
Y
,
a
OF PROTECTION
External radiation The b a s i c m e t h o d s of p r o t e c t i o n which can be u s e d to deal with e x t e r n a l r i s k s and which apply to the u s e of m a c h i n e s e m i t t i n g ionizing r a d i a t i o n s and s e a l e d s o u r c e s of r a d i o active s u b s t a n c e s a r e : 1
R e s t r i c t i o n of the s t r e n g t h of e v e r y s o u r c e
2
Shielding of s o u r c e s
286
n o n - d e s t r u c t i v e t e s t i n g August 1968
c
Fig. 1 Suitable arrangement f o r d o o r interlock. Mounting for positively interlocked switch for hinged door (based on an idea supplied by Pyrotenax Ltd)
W a r n i n g s i g n a l s should always be p r o v i d e d in the v i c i n i t y of x - r a y equipment s o that any one working in t h e a r e a i s a w a r e w h e t h e r o r not the equipment i s e n e r g i z e d . T h i s should b e by w a r n i n g l i g h t s o r audible s i g n a l s o r both, d e pending on c i r c u m s t a n c e s . The b e s t f o r m of w a r n i n g l i g h t i s an i n t e r n a l l y i l l u m i n a t e d sign with the w o r d s ' x - r a y s on' mounted at the e n t r a n c e of the e n c l o s u r e so that it can e a s i l y be s e e n f r o m any d i r e c t i o n . W h e n e v e r p o s s i b l e t h e s e w a r n ings should o p e r a t e a u t o m a t i c a l l y and be d e s i g n e d to fail s a f e . T h e r e may be i n s t a n c e s when it would be i m p r a c t i c a b l e or u n r e a s o n a b l e to c o n s t r u c t w a l l e d e n c l o s u r e s , a s for e x a m p l e when x - r a d i o g r a p h y e q u i p m e n t i s u s e d only v e r y o c c a s i o n a l l y , w h e r e l a r g e c a s t i n g s a r e difficult to m o v e , and when s i t e w o r k i s c o n c e r n e d . In such c i r c u m s t a n c e s d i s t a n c e p r o t e c tion would be r e q u i r e d (for p r e m i s e s u n d e r the F a c t o r i e s Act, s e e Regulation 33(1)(b) in Ref 3). The r a d i o g r a p h y equipment would need to be i s o l a t e d f r o m all o t h e r w o r k by m e a n s of a d e m a r c a t i n g b a r r i e r at s u c h a d i s t a n c e , and taking into account the t i m e in which the tube would be e n e r g i z e d , that 'adequate s h i e l d i n g ' would be p r o v i d e d for any p e r s o n outside the b a r r i e r . Suitable w a r n i n g n o t i c e s should b e a r r a n g e d at the b a r r i e r and the a r e a should be u n d e r s u p e r v i s i o n to e n s u r e no unauthorized e n t r y beyond the b a r r i e r .
(b) X-ray fluoroscopy equipment
(c) X-ray crystallography equipment P a r t i c u l a r c a r e is n e e d e d in the use of x - r a y c r y s t a l l o g r a p h y equipment b e c a u s e the v e r y high d o s e r a t e n e a r the t a r g e t a r e a can c a u s e injury in a v e r y s h o r t t i m e . The e q u i p m e n t should a l w a y s be o p e r a t e d so that it is ' a d e quately s h i e l d e d ' w h e n e v e r the tube i s e n e r g i z e d . To p r e v e n t f i n g e r s o r any o t h e r p a r t s of the body b e i n g ins e r t e d into the p r i m a r y b e a m each p o r t or a p e r t u r e of the x - r a y tube housing m u s t be p r o v i d e d with an automatic b e a m s h u t t e r s o a r r a n g e d that it can only be opened when the c o l l i mating s y s t e m is in p o s i t i o n . Since a p p r e c i a b l e s c a t t e r i n g of the useful x - r a y b e a m can occur, if it p a s s e s u n s h i e l d e d b e t w e e n the tube a p e r t u r e and the (first) c o l l i m a t o r of the a p p a r a t u s in u s e at the a p e r t u r e , t h i s p a r t of the useful b e a m should be c o m p l e t e l y e n c l o s e d to p r o v i d e adequate shielding ( s e e Regulation 37 in Ref 3). A l a b y r i n t h p a t t e r n , made of coupling, is usually the b e s t method. P r e c a u t i o n s m u s t a l s o b e taken to p r e v e n t e x p o s u r e , p a r t i c u l a r l y to f i n g e r s and hands and e y e s , during a l i g n m e n t . It should be e n s u r e d that all p e r s o n s in the vicinity a r e w a r ned that the equipment i s about to be e n e r g i z e d , and when it is energized.
(d) Sealed sources of radioactive substances
S i m i l a r p r e c a u t i o n s a r e r e q u i r e d when x - r a y s a r e u s e d for f l u o r o s c o p y . The e n c l o s u r e p r o v i d i n g 'adequate s h i e l d i n g ' is usually in the f o r m of a cabinet with i n t e r l o c k e d a c c e s s p a n e l s . The d e s i g n of the equipment should e n s u r e that the useful b e a m cannot fall o u t s i d e the s c r e e n and when r e a s o n ably p r a c t i c a b l e , the s c r e e n should be viewed i n d i r e c t l y o r by i m a g e i n t e n s i f i c a t i o n . It should be e m p h a s i z e d that all m a c h i n e s o r a p p a r a t u s e m i t t i n g ionizing r a d i a t i o n s should be thoroughly c h e c k e d a f t e r any a l t e r a t i o n o r t r a n s f e r to a n o t h e r s i t e . F o r e x a m p l e the o m i s s i o n to check that the viewing s c r e e n is in p o s i t i o n in x - r a y f l u o r e s c e n t equipment can and has r e s u l t e d in o v e r - e x p o s u r e of the o p e r a t o r .
When r a d i o a c t i v e s u b s t a n c e s in the f o r m of s e a l e d s o u r c e s a r e u s e d , the p r e c a u t i o n s a r e in many r e s p e c t s s i m i l a r to t h o s e r e q u i r e d for x - r a y equipment. The s a m e b a s i c p r i n c i p l e s of p r o t e c t i o n should be applied. The b e s t a r r a n g e m e n t for the p o w e r f u l g a m m a - e m i t t i n g s o u r c e s u s e d for g a m m a r a d i o g r a p h y is to p r o v i d e a s e p a r a t e r o o m , for which the amount of shielding and d i s t a n c e p r o t e c t i o n p r o v i d e d should c o n s t i t u t e 'adequate shielding.' F a c i l i t i e s for r e m o t e handling o r r e m o t e control of s e a l e d s o u r c e s of r a d i o a c t i v e m a t e r i a l should always be p r o v i d e d . All m a n i p u l a t i o n s should be c o m p l e t e d b e f o r e the s o u r c e is e x p o s e d . T r i a l r u n s , using a d u m m y s o u r c e , without exposing the s o u r c e o r e n e r g i z i n g the x - r a y machine a r e d e s i r a b l e for all r a d i o g r a p h i c w o r k . P e r s o n s a u t h o r i z e d to c a r r y out g a m m a r a d i o g r a p h y should 0rdy have a c c e s s to the a r e a f o r the m i n i m u m t i m e and only under conditions which e n s u r e they a r e adequately p r o t e c t e d . When a s e a l e d s o u r c e of r a d i o a c t i v e s u b s t a n c e s is u s e d in a static e l i m i n a t o r , t h i c k n e s s gauge o r s i m i l a r device, it m u s t not only b e 'adequately s h i e l d e d ; but be p r o v i d e d with a s u i table c o v e r plate o r s h u t t e r so that the useful b e a m i s a t t e nuated, so f a r a s i s r e a s o n a b l y p r a c t i c a b l e , when not in u s e .
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B e c a u s e of the p o s s i b i l i t i e s of d a m a g e to s e a l e d s o u r c e s t h e r e a r e r e q u i r e m e n t s a s to action to be taken In the event of leakage o r b r e a k a g e . They should be t e s t e d for leakage and consequent s u r f a c e contamination by a qualified e x p e r t , at l e a s t o n c e in e v e r y 26 m o n t h s , o r i m m e d i a t e l y if a leak is suspected.
Internal radiation
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Special h a z a r d s a r e a s s o c i a t e d with the u s e of u n s e a l e d r a d i o a c t i v e s u b s t a n c e s b e c a u s e p r e c a u t i o n s have to be taken a g a i n s t the r i s k s of i n t e r n a l r a d i a t i o n a s w e l l a s e x t e r n a l radiation. The r e q u i r e m e n t s depend on the s t r e n g t h of the s o u r c e s involved, the r a d i o t o x i c i t y , c h e m i c a l toxicity and o t h e r c h e m i cal and p h y s i c a l p r o p e r t i e s a s well a s the nature of the o p e r a t i o n s . T h e r e a r e again l o w e r l i m i t s of activity below which the R e g u l a t i o n s and Code of P r a c t i c e do not apply. The b a s i c m e t h o d s of p r o t e c t i o n which n e e d to be taken to m i n i m i z e the d e p o s i t i o n within the body of r a d i o a c t i v e subr s t a n c e s , w h e t h e r by inhalation, ingestion o r o t h e r m e a n s are." 1
Fig. 2 Mounting f o r p o s i t i v e l y i n t e r l o c k e d switch f o r sliding door
The u s e of m a t e r i a l of m i n i m u m radtotoxicity
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W h e r e n e c e s s a r y , u s e of p r o t e c t i v e equipment n o n - d e s t r u c t i v e t e s t i n g August 1968
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P r o t e c t i o n against i n t e r n a l r a d i a t i o n i s b e s t a c h i e v e d by s e p a r a t i o n and containment of all o p e r a t i o n s with u n s e a l e d r a d i o a c t i v e s u b s t a n c e s . The a r e a s d e s i g n a t e d for such work should be c l e a r l y m a r k e d (see Regulation 2 in Ref 4 and p a r a g r a p h 9 . 2 . 1 in Ref 5).
When p r o t e c t i v e clothing is provided, suitable a c c o m m o d a t i o n for changing and s t o r a g e should be available. Special a r r a n g e m e n t s will need to be made for cleaning o r washing p r o t e c tive clothing c o n t a m i n a t e d above the m a x i m u m p e r m i s s i b l e l e v e l s for s u r f a c e contamination.4, 5
The m o s t effective way of providing c o n t a i n m e n t and l i m i t i n g the s p r e a d of contamination is to a r r a n g e for the w o r k to be c a r r i e d out in a total e n c l o s u r e . T h i s should be in the f o r m of a glove box for handling the m o s t toxic r a d i o a c t i v e m a t e r i a l s (i.e. C l a s s I in the c l a s s i f i c a t i o n of Radionuclides), a n d / o r r a d i o a c t i v e m a t e r i a l in p a r t i c u l a r f o r m . In o t h e r c a s e s an efficient fume cupboard may p r o v i d e a sufficient f o r m of e n c l o s u r e . Both total e n c l o s u r e s and fume c u p b o a r d s m u s t have m e c h a n i c a l exhaust e x t r a c t i o n to p r e v e n t the e s c a p e of a i r b o r n e r a d i o a c t i v e m a t e r i a l into the w o r k r o o m or laboratory.
E a s i l y a c c e s s i b l e washing f a c i l i t i e s should be p r o v i d e d and s t a n d a r d s a r e laid down a s to design and n u m b e r of w a s h b a s i n s a c c o r d i n g to the n u m b e r of p e r s o n s c o n c e r n e d . Hands should be w a s h e d and checked for contamination b e f o r e l e a v ing the a r e a .
(a) Design and equipment T h e r e a r e r e q u i r e m e n t s about the d e s i g n and type of equipm e n t that should be u s e d for e x p e r i m e n t a l work in f a c t o r y p r o c e s s e s , in p r o c e s s c o n t r o l l a b o r a t o r i e s o r in r e s e a r c h e s t a b l i s h m e n t s . F l o o r s , w a l l s , c e i l i n g s and b e n c h tops should have s m o o t h i m p e r v i o u s s u r f a c e s which can be e a s i l y c l e a n e d and d e c o n t a m i n a t e d . A trouble spot for contamination can b e found in gaps in floor c o v e r i n g s , so joints should be e f f e c t i v e ly s e a l e d , and ledges and i n a c c e s s i b l e p l a c e s liable to c o l l e c t dust should be e l i m i n a t e d a s f a r a s p o s s i b l e . The layout of equipment will v a r y a c c o r d i n g to c i r c u m s t a n c e s and only e s s e n t i a l f u r n i t u r e and fittings should be allowed. C a r e should be taken to e n s u r e e a s y a c c e s s to adequate m e a n s of e s c a p e in the event of f i r e or o t h e r e m e r g e n c y such a s s p i l l s o r e s c a p e of r a d i o a c t i v e m a t e r i a l s .
(b) Methods of work Methods of w o r k with u n s e a l e d r a d i o a c t i v e s u b s t a n c e s have to be such a s to avoid s p i l l s o r c r e a t i n g d u s t . A p p a r a t u s and equipment u s e d for t h i s work should not be u s e d for o t h e r p u r p o s e s u n l e s s it has b e e n checked f o r contamination. The mouth must not c o m e into contact with any apparatus; for example, p i p e t t e s must be o p e r a t e d by o t h e r m e a n s . B r u s h e s m u s t not be u s e d for the application of luminizing compounds, but if u s e d for the a p p l i c a t i o n o f o t h e r r a d i o a c t i v e s u b s t a n c e s the o p e r a t i o n m u s t only be c a r r i e d out in a total e n c l o s u r e . The s t a n d a r d of c l e a n l i n e s s m u s t be v e r y high in a r e a s u s e d for work with r a d i o a c t i v e s u b s t a n c e s and routine cleaning, by m e t h o d s which avoid s p r e a d of contamination, should be c a r r i e d out at frequent i n t e r v a l s to p r e v e n t r e s i d u a l c o n t a m i nation f r o m exceeding the p e r m i t t e d l e v e l s (see Schedule 2 in Ref 4 and Appendix 2 in Ref 5). M a t e r i a l s and equipment u s e d for cleaning should not be u s e d outside t h e s e a r e a s , o t h e r w i s e t h e r e is r i s k of s p r e a d of contamination.
(c) Personal hygiene T h e r e a r e s p e c i a l r e q u i r e m e n t s a s to p e r s o n a l hygiene to p r e v e n t ingestion, inhalation o r o t h e r a b s o r p t i o n of r a d i o a c tive m a t e r i a l . Eating, drinking, smoking, taking of snuff and the application of c o s m e t i c s m u s t obviously not take p l a c e in a r e a s subject to c o n t r o l . O r d i n a r y h a n d k e r c h i e v e s should not be used; p a p e r h a n d k e r c h t e v e s should b e p r o v i d e d and used, and a f t e r u s e should be d i s p o s e d of a s r a d i o a c t i v e w a s t e . T h e r e a r e a l s o r e q u i r e m e n t s for p r o t e c t i o n of cuts or b r e a k s in the skin which must b e c h e c k e d a s to d r e s s i n g s and c o v e r ings and if contamination i s p r e s e n t the f a c t s m u s t be r e p o r t e d a s soon a s p o s s i b l e for i n v e s t i g a t i o n and m e d i c a l s u r v e i l l a n c e if n e c e s s a r y .
Storage and t r a n s p o r t within p r e m i s e s Another i m p o r t a n t a s p e c t of p r o t e c t i o n is that a r r a n g e m e n t s must be made f o r all s o u r c e s , both s e a l e d and unsealed, to be s e c u r e l y s t o r e d when not in use. The s t o r e should be 'adequately s h i e l d e d ' and if r a d i o a c t i v e gas, dust or vapour i s liable to be p r e s e n t , the s t o r e will need to be efficiently ventilated by m e c h a n i c a l m e a n s . The s t o r e should be so c o n s t r u c t e d a s to m i n i m i z e the r i s k f r o m f i r e and should be in the c h a r g e of a r e s p o n s i b l e p e r s o n . The b a s i c p r i n c i p l e s of p r o t e c t i o n should be applied when r a d i o a c t i v e s u b s t a n c e s a r e t r a n s p o r t e d within the f a c t o r y or r e s e a r c h e s t a b l i s h m e n t . C o n t a i n e r s should p r o v i d e ' a d e quate s h i e l d i n g ' and c o n t a i n e r s used f o r u n s e a l e d r a d i o a c t i v e s u b s t a n c e s should be d e s i g n e d and c o n s t r u c t e d so a s to p r e vent the s p r e a d of contamination or d i s p e r s a l of g a s e o u s radioactive substances. U p - t o - d a t e r e c o r d s should be kept of all r a d i o a c t i v e subs t a n c e s and in the c a s e of u n s e a l e d s o u r c e s , w h e r e a p p r o p r i a t e , the date and m a n n e r of t h e i r subsequent d i s p o s a l . If the accounting s y s t e m s h o w s that a s o u r c e has b e e n lost or m i s l a i d , the p e r s o n in c h a r g e m u s t be notified without delay so that p r o m p t action can be taken for i t s r e c o v e r y . All p r o t e c t i v e c o n t a i n e r s u s e d for r a d i o a c t i v e s o u r c e s should be c l e a r l y l a b e l l e d by a distinguishing n u m b e r o r identifying m a r k to avoid e r r o r s and p o s s i b l e r i s k of e x c e s s i v e r a d i a tion when s o u r c e s a r e i s s u e d f r o m the s t o r e . Radiological and m e d i c a l s u p e r v i s i o n P e r s o n s who a r e d e s i g n a t e d a s ' c l a s s i f i e d w o r k e r s ' can only be p e r m i t t e d to work in conditions w h e r e they a r e likely to r e c e i v e m o r e than t h r e e t e n t h s of the annual m a x i m u m p e r m i s s i b l e d o s e s if they a r e subject to p e r s o n a l m o n i t o r i n g and m e d i c a l s u p e r v i s i o n . In c u r r e n t l e g i s l a t i o n and the Code of P r a c t i c e the method r e q u i r e d for p e r s o n a l m o n i t o r i n g is t h e w e a r i n g of a suitable photographic f i l m in an a p p r o p r i a t e holder o r o t h e r suitable d o s e m e t e r . The f i l m badge should be obtained f r o m an a p p r o v e d l a b o r a t o r y such a s the Radiological P r o t e c t i o n S e r v i c e * and they should be r e t u r n e d for examination a f t e r being w o r n . It will be a d v i s a b l e to a r r a n g e for b i o l o g i c a l m o n i t o r i n g (evaluation of a m o u n t s of r a d i o a c t i v e s u b s t a n c e s in the body by m e a s u r e m e n t of the a m o u n t s being e x c r e t e d or. o t h e r a p p r o p r i a t e m e a n s ) , w h e r e significant a m o u n t s of m o r e h a z a r d o u s m a t e r i a l s such a s plutonium, radium, s t r o n t i u m , polonium, c a e s i u m or r a d i o - i o d i n e a r e u s e d . Biological m o n i t o r i n g is the only f e a s i b l e m e t h o d f o r t e s t i n g for p e r s o n a l e x p o s u r e to the weak b e t a e m i t t e r s such a s t r i t i u m , c a r b o n 14 and sulphur 35. Radiation r e c o r d s a r e r e q u i r e d to be kept to p r o v i d e a c o n tinuous check on the extent of d o s e s r e c e i v e d . ' C l a s s i f i e d w o r k e r s ' should r e c e i v e p e r i o d i c m e d i c a l e x a m i nations so long a s they continue to be e n g a g e d in t h i s work. To p r e v e n t the e m p l o y m e n t of p e r s o n s not fit f o r t h i s work initial m e d i c a l e x a m i n a t i o n s a r e a l s o r e q u i r e d . R e c o r d s of t h e s e e x a m i n a t i o n s a r e e s s e n t i a l to enable the health of the p e r s o n s c o n c e r n e d to be kept under c o n s t a n t r e v i e w .
(d) Protective equipment Ideally, the f i r s t line of p r o t e c t i o n is to s a f e g u a r d the s o u r c e , but w h e r e u n s e a l e d r a d i o a c t i v e s u b s t a n c e s a r e u s e d , p r o t e c tive equipment is r e q u i r e d to p r e v e n t the p o s s i b i l i t y of c o n t a m i n a t i o n of skin, hair and p e r s o n a l clothing. F o r c e r t a i n o p e r a t i o n s , b r e a t h i n g a p p a r a t u s should be available, p a r t i c u l a r l y w h e r e t h e r e i s liable to be a h a z a r d f r o m g a s e o u s or a i r b o r n e r a d i o a c t i v e m a t e r i a l . T h e r e a r e r e q u i r e m e n t s for the b r e a t h i n g apparatus to be e x a m i n e d and t e s t e d .
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non-destructivetesting August 1968
Monitoring of the working environment The e f f e c t i v e n e s s of p r o t e c t i v e m e a s u r e s must be a s s e s s e d by r e g u l a r m o n i t o r i n g of the working e n v i r o n m e n t , to check the l e v e l s of e x t e r n a l r a d i a t i o n and the amount of c o n t a m i n a tion on s u r f a c e s . A p p r o p r i a t e m o n i t o r i n g i n s t r u m e n t s m u s t
* Clifton Avenue,Belmont,Sutton,Surrey, England
t h e r e f o r e be p r o v i d e d and they should b e t e s t e d and calibrated when f i r s t t a k e n into u s e a n d r e - t e s t e d and r e - c a l i b r a t e d p e r i o d i c a l l y (at l e a s t once in e v e r y 14 m o n t h s in factory premises).
REFERENCES I n t e r n a t i o n a l C o m m i s s i o n on R a d i o l o g i c a l P r o t e c t i o n I C R P P u b l i c a t i o n 2. R e p o r t of C o m m i t t e e H on P e r m i s s i b l e Dose for I n t e r n a l Radiation, 1959. P e r g a m o n P r e s s
S u p e r v i s i o n a n d tr~inlru~ T h e p r i m a r y r e s p o n s i b i l i t y f o r o b s e r v a n c e of t h e l e g a l r e q u i r e m e n t s and r e c o m m e n d a t i o n s of t h e Code of P r a c t i c e r e s t s with the f a c t o r y o c c u p i e r o r t h e c o n t r o l l i n g a u t h o r i t y of t h e r e s e a r c h e s t a b l i s h m e n t . An a d m i n i s t r a t i v e o r g a n i z a tion should be s e t up to m a t c h the extent a n d c h a r a c t e r of these responsibilities. P e r s o n s a p p o i n t e d to e x e r c i s e s u p e r v i s i o n and to a s s i s t with the r e q u i r e m e n t s for r a d i o l o g i c a l s a f e t y should be c o m p e tent to d e a l w i t h the n a t u r e of the work a n d the r i s k s i n v o l v e d and e x e r c i s e s u r v e i l l a n c e of a l l e q u i p m e n t and p l a n t . All p e r s o n s l i a b l e to b e e x p o s e d to ionizing r a d i a t i o n s a r e r e q u i r e d to be i n s t r u c t e d about the h a z a r d s i n v o l v e d in t h e w o r k a n d about the p r e c a u t i o n s to b e o b s e r v e d . T h e extent of t h e i n s t r u c t i o n will depend on the n a t u r e of t h e w o r k and a p p r o p r i a t e c o u r s e s of i n s t r u c t i o n s a r r a n g e d w h e r e n e c e s s a r y .
ICRP P u b l i c a t i o n 9. R e c o m m e n d a t i o n s of the I n t e r n a t i o n a l C o m m i s s i o n on R a d i o l o g i c a l P r o t e c t i o n . Pergamon Press 3
T h e I o n i s i n g R a d i a t i o n s (Sealed S o u r c e s ) R e g u l a t i o n s 1961 (SI 1961 No 1470). H e r M a j e s t y ' s S t a t i o n e r y Office
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T h e Ionising R a d i a t i o n s ( U n s e a l e d R a d i o a c t i v e Subs t a n c e s ) R e g u l a t i o n s 1968 (SI 1968 No 780). HMSO
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Code of P r a c t i c e for the p r o t e c t i o n of p e r s o n s exposed to Ionising R a d i a t i o n s in R e s e a r c h a n d T e a c h i n g . HMSO 'A handbook of d a t a for r a d i o l o g i c a l p r o t e c t i o n ' , p r e p a r e d by a p a n e l of the R a d i o a c t i v e S u b s t a n c e s A d v i s o r y C o m m i t t e e (to b e p u b l i s h e d s h o r t l y )
ACKNOWLEDGEMENTS T h e a u t h o r w i s h e s to t h a n k H M Chief I n s p e c t o r of F a c t o r i e s , M r W. J . C. P l u m b e , b y w h o s e p e r m i s s i o n t h i s a r t i c l e i s published.
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' E l e c t r i c a l l i m i t s w i t c h e s and t h e i r application', Safety, Health and W e l f a r e P a m p h l e t , New s e r i e s No 24. HMSO
n o n - d e s t r u c t i v e t e s t i n g August 1968
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