Composition, decontamination of radioactive gas mixtures

VACUUM Classified A b s t r a c t s

IV --

Special

4o ~

0

Subsidiary

GASES

AND

Subjects

VAPOURS

--

--

IV

Abstract No. and References

4°

A Graphical Approach to Vacuum Engineering See A b s t r a c t No. : 137/I

38/IV

Specific Gravity of Gases United States, Six m e t h o d s of m e a s u r i n g t h e specific g r a v i t y of a g a s are described. Tile first t w o give direct r e a d i n g s , are basic m e t h o d s a n d require t h e u s e of v a c u u m e q u i p m e n t . T h e r e m a i n i n g four n e e d calibration. (1) The Direct-Weighing method is a l a b o r a t o r y m e t h o d . T h e w e i g h t of a globe filled w i t h air is c o m p a r e d w i t h t h e w e i g h t of t h e s a m e globe filled w i t h t h e g a s u n d e r t e s t a t t h e s a m e p r e s s u r e a n d t e m p e r a t u r e . T h e a p p a r a t u s c o n s i s t s of t w o globes of e q u a l size, o n e of w h i c h is p e r m a n e n t l y e v a c u a t e d a n d acts as t h e c o u n t e r b a l a n c e to tile other, t h e weighing, globe. F i r s t t h e w e i g h i n g globe is e v a c u a t e d , its o w n w e i g h t is d e t e r m i n e d a n d t h e b a l a n c e b e t w e e n t h e t w o globes is a d j u s t e d accordingly. T h e n , t h e w e i g h i n g globe is filled w i t h t h e g a s to be t e s t e d at a p r e s s u r e as n e a r as possible to a t m o s p h e r i c pressure. W h e n t e m p e r a t u r e e q u i l i b r i u m h a s b e e n reached, t h e globe is weighed a n d t h e t o t a l w e i g h t of t h e s a m p l e a n d t h e globe is recorded. T h i s is followed b y w e i g h i n g t h e globe a f t e r filling it w i t h air b y t h e s a m e procedure. A s k e t c h is s h o w n of t h e filling a r r a n g e m e n t . T h e specific g r a v i t y c a n t h e n be c a l c u l a t e d from: (Wgas X Pair × Tgas)/(Wair X Pgas X Taft) (2) The Gas Balance method is b a s e d o n A r c h i m e d e s ' principle, i.e. t h e w e i g h t of a g i v e n v o l u m e of a s u b s t a n c e i m m e r s e d in a liquid or g a s is e q u a l to t h e w e i g h t of t h e liquid or g a s displaced. Specific g r a v i t y in t h i s case is i n d i c a t e d b y r e c o r d i n g b u o y a n c y . T h r e e v a r i e t i e s of t h e m e t h o d are discussed: (a) T h e E d w a r d s Balance, (b) t h e Ac-IVIe S u s p e n s i o n - T y p e B a l a n c e a n d (c) t h e A n u b i s D i r e c t - R e a d i n g Balance. I n t h e case of t h e first a float is a t t a c h e d to a b a l a n c e b e a m enclosed in a n a i r - t i g h t c h a m b e r . T h e c h a m b e r is e v a c u a t e d , p u r e air is a d m i t t e d at a p r e s s u r e sufficient to m o v e t h e float i n d i c a t o r to t h e n u l l - b a l a n c i n g position. T h e n , t h e c h a m b e r is e v a c u a t e d a g a i h a n d t h e g a s to be t e s t e d is a d m i t t e d u p to a p r e s s u r e to m o v e t h e i n d i c a t o r to t h e m a r k e d b a l a n c i n g position. T h e r e s p e c t i v e p r e s s u r e recordings, a n d m a n o m e t e r a n d b a r o m e t e r r e a d i n g s facilitate t h e c a l c u l a t i o n of t h e specific g r a v i t y of t h e gas. T h e A t - M e b a l a n c e h a s a different s u s p e n s i o n s y s t e m a n d r e q u i r e s larger s a m p l e s for m e a s u r e m e n t . T h e A.nubis i n s t r u m e n t facilitates t h e r e a d i n g of t h e specific g r a v i t y directly f r o m t h e scale. (3) The Effusion method is b a s e d on t h e p h e n o m e n o n t h a t t h e r a t e of flow of a g a s t h r o u g h a n orifice of g i v e n d i m e n s i o n s d e p e n d s on its specific g r a v i t y . A t y p i c a l a p p a r a t u s o p e r a t i n g according to t h i s m e t h o d is t h e Schilling's Bottle. D e t a i l s of its o p e r a t i o n are given. (4) The Viscous-Drag method is r e p r e s e n t e d b y a d e s c r i p t i o n of t h e R a n a r e x G r a v i t o m e t e r . T h e i n s t r u m e n t h a s t w o c h a m b e r s , a gas c h a m b e r a n d a n air c h a m b e r . E a c h c h a m b e r is f i t t e d w i t h a m o t o r - d r i v e n fan, m o v i n g a t c o n s t a n t speed, a n d a freely r o t a t i n g i m p u l s e wheel. T h e air a n d g a s a d m i t t e d to t h e r e s p e c t i v e c h a m b e r s receive a r o t a t i n g m o t i o n b y t h e f a n a n d e x e r t a t o r q u e o n t h e i m p u l s e w h e e l in e a c h c h a m b e r . A s t h e f a n s r o t a t e in opposite directions t h e t o r q u e e x e r t e d on t h e i m p u l s e wheels oppose e a c h other. T h e s h a f t s of t h e i m p u l s e wheels are l i n k e d m e c h a n i c a l l y a n d t h e differential of t h e t w o t o r q u e s is i n d i c a t e d b y a pointer. T h e i n s t r u m e n t is suitable for c o n t i n u o u s recording a n d r e q u i r e s 6 ft. a p.h. of a p p r o x i m a t e l y a t m o s p h e r i c p r e s s u r e g a s for its operation. (5) The Kinetic-PressureIncrease method is r e p r e s e n t e d b y a d e s c r i p t i o n of t h e Metric G r a v i t o m e t e r a n d (6) the Air-Column-Weighing method b y a d e s c r i p t i o n of t h e A n u b i s D i r e c t - W e i g h t T y p e of G r a v i t o m e t e r . Sommaire : Six m d t h o d e s de m e s u r e de la gravitd spdcifique des gaz s e n t d6crites.

39/IV

Article by B. J. Willard I~struments 27~ June 1954 9,15-949

0 Ionisation and Excitation of Mercury Vapour by Positive Ion Impact

40/IV

See AbstractNo. : 156/I

Composition, Decontamination of Radioactive Gas Mixtures United States. I n t h e o p e r a t i o n of a ' W a t e r - B o i l e r ' r e a c t o r t h e u r a n y i - n i t r a t e solution in n a t u r a l w a t e r is radiolyrically d e c o m p o s e d r e s u l t i n g in t h e liberation of h y d r o g e n , o x y g e n , n i t r o g e n a n d fission p r o d t m t s w h i c h m i x w i t h t h e air f l u s h e d t h r o u g h t h e s y s t e m to keep t h e r a d i o a c t i v e gas a w a y f r o m t h e p r e s s u r e g a u g e lines. I n a r e c o m b i n a t i o n s y s t e m h y d r o g e n a n d o x y g e n is c o n v e r t e d into w a t e r w h i c h is r e t u r n e d to t h e solution in t h e reactor. A d e s c r i p t i o n is g i v e n of a m i c r o - v o l u m e t r i c s y s t e m facilitating t h e a n a l y s i s of t h e 'off-gas' m i x t u r e . T h i s gas m i x t u r e is h i g h l y r a d i o a c t i v e b e c a u s e of t h e presence of p r o d u c t s of t h e i o d i n e - b r o m i n e d e c a y c h a i n s u c h as x e n o n a n d k r y p t o n . Iodine, for i n s t a n c e , c o n s t i t u t e s a serious h e a l t h h a z a r d a n d t h e r e f o r e t h e l i m i t of 8 - d a y p a l p e r m i s s i b l e in b r e a t h a b l e air h a s b e e n set a t 3 × l0 -9 m c / 1 . T h u s o n l y v e r y s m a l l s a m p l e s c a n be used. T h e a l l - g l a s s a p p a r a t u s u s e d for t h e a n a l y s i s is s h o w n in a n illustration. M e r c u r y cut-offs are e m p l o y e d t h r o u g h o u t , i n s t e a d of m e c h a n i c a l valves. A m e r c u r y diffusion p u m p is u s e d for e v a c u a t i o n . T h e g a s s a m p l e to be a n a l y s e d is supplied in closed t u b e s w h i c h are sealed to t h e s t o r a g e b u l b of t h e s y s t e m . A 2 0 0 - m l . a u t o m a t i c a l l y controlled Toepler p u m p is e m p l o y e d for direct t r a n s m i s s i o n of t h e s a m p l e to t h e 5 0 - m l . m e a s u r i n g bulb, or, a l t e r n a t i v e l y , for circulation of t h e s a m p l e over t h e r e a g e n t s used for t h e r e m o v a l of its i n d i v i d u a l c o m p o n e n t s . T h e d e t e r m i n a t i o n proceeds in tile following order: C a r b o n dioxide p l u s m o i s t u r e b y freezing w i t h liquid n i t r o g e n , m o i s t u r e a f t e r s e p a r a t i o n f r o m c a r b o n dioxide b y f r a c t i o n a l s u b l i m a t i o n , h y d r o g e n b y c o m b u s t i o n w i t h o x y g e n , o x y g e n b y o x i d a t i o n of h o t copper, n i t r o g e n b y r e a c t i o n w i t h h o t u r a n i u m t u r n i n g s a n d i n e r t g a s e s b y difference. D e t a i l s of t h e p r o c e d u r e are given. I t follows a description of t h e m e t h o d e m p l o y e d

July, I954

Vacuum Vol. I V No. 3

41/IV

390

VACUUM

Classified A b s t r a c t s

IV ~

Special

Subsidiary Contd.

for the collection of the gas s a m p l e s to be analysed. collected is given in the table r e p r o d u c e d below.

Subjects ~

IV

Abstract No. ana References

An indication of the radioactivity of t h e sample w h e n

Radioactive Gases from Fission with Half-Lives Greater than One Minute Br 8. Br 8s

35 h 2.4 h

Br*' Br 86

33 m 3 m

O

2.8 h 2.6 m

I x*o

1.4 m

XoT M

12 d

I~*,

108 y

I~

2.0 d

Xe tas Xe ~.5

5.27 d 13 m

Xe t*~ X& *~

9.2 h 3.9 m

Xe ~8.

17 m

Kr ~3 Kr ~

1.9 h 4.4 h

I '~*

2.4 h

I ~aa

22 h

Kr 8~

9.4 y 78 m

I TM I ~85 •

Kr s7

O

Kr .8 Kr 8.

54 m 6.7 h

The t o t a l i n t e n s i t y at the time of collection exceeded 1 c . / m l . N.T.P. The collection s y s t e m contained a 1-1itre receptacle w h e r e the gas w a s left to decay for 2 days before it w a s transferred to the analytical system. I t s a c t i v i t y was t h e n reduced to 20 m r . / m l . All valves in the collection s y s t e m were remote-controlled and pressure m e a s u r e m e n t s were t a k e n f r o m a distance of 2 metres. The whole of the collection s y s t e m w a s shielded w i t h 8 - i n c h lead. The results of a typical analysis are given in t a b u l a r form. Finally three m e t h o d s for the f u r t h e r d e c o n t a m i n a t i o n of the gas (after use in the analysis) are described. The first provides for a slight delay and a large dilution b y air in a stack. The second relies on the use of delay t a n k s where the gas m i x t u r e is left to decay for a considerable time. Numerical values are s h o w n in graphs. The t h i r d m e t h o d consists of passing the radioactive gas s t r e a m over activated charcoal which a b s o r b s the radioactive c o m p o n e n t s . 100 kg. of charcoal per m o n t h would be a d e q u a t e to effect d e c o n t a m i n a t i o n of the gas s t r e a m evolved from a w a t e r boiler operated at a m a x i m u m p o w e r of 30 k W for 6 h o u r s every day. Sommaire : On discute les m6thodes & a n a l y s e des gaz radioactifs liber6s p a r la decomposition de nitrate d ' u r a n y l qui se fair dans une chaudi6re de r6acteur.

Determination of Oxygen in C e r t a i n G a s e s United States. P r e s e n t - d a y studies of corrosion of m e t a l s b y liquids necessitate the p r e p a r a t i o n and analysis of inert gas b l a n k e t s free, or nearly free, of oxygen. M i c r o - a m o u n t s of o x y g e n m a y be determined in the inert gases, hydrogen, nitrogen, and c a r b o n dioxide by a modification of t h e Winkler m e t h o d , in which the o x y g e n is a b s o r b e d in m a n g a n o u s h y d r o x i d e ; an equivalent a m o u n t of iodine is liberated, t h e n extracted into o-xylene and determined colorimetrically. The analysis takes place at low pressures, from 350 to 760 m m . Hg, w h e r e b y a small v o l u m e of gas (250 to 500 millilitres) can be analysed. A reproducibility of 0.7 p a r t s per million or b e t t e r w a s o b t a i n e d over a range of 0 to 25 p a r t s per million of o x y g e n (microlitres per litre). The m e t h o d can be e x t e n d e d to 150 p a r t s per million of oxygen b y e x t r a c t i n g into larger q u a n t i t i e s of o-xylene. I m p r o v e d m e t h o d s of r e m o v i n g dissolved o x y g e n from analytical reagents result in a constant, b u t low, b l a n k which p e r m i t s the degree of precision obtained. (Nuclear Science Abstracts) Sommaire : On d o n n e des d6tails sur la d6termination de micro-quantit6s d'oxyg~ne dans des gaz inertes, hydrog6ne, azote et oxyde de carhone, p a r la m6thode modifi6e de Winkler.

D e t e r m i n a t i o n of L o w C o n c e n t r a t i o n s of O x y g e n in H y d r o g e n

Article by H. M. Busey 1"~ucleonies 12, May 1954 9-13

42/IV

Report by L. Silverman and W. Bradshaw A E C . Rep. No. NAA-SR-892 April 1954

43/IV

Canada. I n order to facilitate the s t u d y of poisoning of an i r o n - s y n t h e t i c a m m o n i a c a t a l y s t b y o x y g e n an analytical m e t h o d w a s r e q u i r e d for the d e t e r m i n a t i o n of o x y g e n c o n t e n t r a n g i n g from 1 to 100 p.p.m. The m e t h o d developed for t h e p u r p o s e is based on t h a t b y B a m f o r d & Baldwin which facilitates d e t e r m i n a t i o n s d o w n to 0.01% oxygen. The new m e t h o d h a s a lower limit of 0.00005% equal 0.5 p.p.m. :t: 10% in the case of a 1.3 litre sample of hydrogen. Essentially t h e e x p e r i m e n t a l e q u i p m e n t consists of a m e r c u r y p i s t o n p u m p which circulates the gas over a p l a t i n u m catalyst; t h e w a t e r v a p o u r formed in the process is passed into a liquidnitrogen t r a p for condensation. The v o l u m e of the condensate is m e a s u r e d at 10 ram. H g pressure in a M c L e o d t y p e gauge. All calibration d a t a and results are given in litre-micron units. 1.3 litres of h y d r o g e n at atmospheric pressure is 1,000,000 l i t r e - m i c r o n and an o x y g e n c o n t e n t of 1 p.p.m, equals 2 litre-micron of w a t e r v a p o u r . Measured at 10 ram. H g this value is represented b y 2 ml. of condensate. T w o different w a t e r v a p o u r gauges were available, one of 5,500 l i t r e - m i c r o n capacity and the o t h e r of 150 l i t r e - m i c r o n capacity. Details of the p l a n t are given in illustrations. The m o s t critical feature of the m e t h o d is the a m o u n t of w a t e r v a p o u r recovered from the gas for m e a s u r e m e n t . I t varies b y the a m o u n t a b s o r b e d by, or desorbed from, the walls (glass) of the e q u i p m e n t . Thus, the t e m p e r a t u r e of the e q u i p m e n t m u s t be k e p t c o n s t a n t during the e x p e r i m e n t w i t h i n 1 or 2 degrees. This necessitates the provision of a cooling jacket for the catalyst. I n addition, all operational times such as circulation, e v a c u a t i o n a n d distillation of w a t e r v a p o u r m u s t be standardised. A full description is given of the p r e c a u t i o n s t a k e n to ensure accurate results. Calibration w a s carried out b y adding k n o w n a m o u n t s of o x y g e n to dry, o x y g e n - f r e e hydrogen. The loss due to a d s o r p t i o n of w a t e r v a p o u r during m e a s u r e m e n t depends on the degree of p r e - a d s o r p t i o n of w a t e r v a p o u r in the gauge. The a m o u n t of p r e - a d s o r b e d w a t e r

J u l y , 1954

Vacuum VoL I V N o ,3

391