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A simple and inexpensive chemical radiation dose indicator
International Journal of Applied Radiation and Isotopes,l970, Vol. 2 I, pp. 177478. Pergamon Press. Printed in Northern Irehnd
A Simple
and Radiation
Inexpensive Chemical Dose Indicator *
(Receiud30 October 1969) CHEMICALdosimeterst14) with suitable ranges and accuracy have found a limited acceptance in a wide area of irradiation services. However, in some particular instances of irradiation procedures a less sophisticated device such as a simple “go-no go” type dose indicator would suffice. A particular example for the need of such a device was presented to us in connection with the “Mediterranean Fruit Fly” eradication programme conducted by various countries on cooperation with the Joint Division of Atomic Energy in Food and Agriculture and the International Atomic Energy Agency. This and some similar eradication programmes of other insect
infested area. Sterilization of the fruit flies is achieved by irradiation with about 8000 rad. rt 15 per cent from a s%o y ray source. Serious consequences could entail if the dose application should be insufficient or if irradiation is accidentally omitted. Millions and millions of fertile flies would then be added to the already excessive insect pest population. Another example of the usefulness of such a device is visualized in radiation effect studies on plants where irradiation is carried out in so-called “Gammagardens”. Small dose indicators such as described below can easily be attached in light tight containers to plants or even inserted into the ground without fear of damage to or loss of expensive instruments. Though only a dose indicator it would nevertheless allow the investigators to obtain an immediately readable indication of the radiation status of the test objects. The low cost of the system makes it particularly attractive for developing countries involved in studies for increasing crop production.
TABLE 1
Preparation number
Proportions of stock solution of chIoral* hydrate solution (ml)
(1) (2) (3)
1 1 1
HsC
Indicator solution
Dose range (krad.)
visually distinguishable dose intervals (kt=U
2 1 0
o-02 0.02 0.02
O-2.5 O-15.0 O-30.0
0.3-0.5 25-5-O 10*0-15~0
Distilled
* Concentrated chloralhydrate solution 0.83 g/ml HsO. pests make use of the so-called “irradiation induced sterile male fly” technique. These insects are irradiated to the extent that their reproductive capabilities are extinct, after emerging from the pupae stage but are otherwise undistinguishable in viability and behaviour from their normal counterparts. After release they compete with normal males in the environment but their mating results only in non-viable offsprings and consequently this particular insect population gradually becomes extinct in the
For such purposes a dosimeter was developed which fulfilled the following requirements. (1) Instant and positive indication that irradiation within the required dose range has been applied to the insects or plants. (2) The dosimeter must be exposed simultaneously with the objects to the radiation. (3) The dosimeter system should be easy to handle by lay people. The system should he cheap and simple to produce in large quantities of the throw-away type. *This work was performed in the Dosimetry (4) The dosimeter system should have a reasonable Section and Dosimetry Laboratory of the International shelf and storage lift and should not be very sensitive Atomic Energy Agency, Vienna, Austria. to climatic influences. 177
L&m
178 Methods
to the editors
and Results
The described dose indicator device made use of the radiation induced cbangea in chloral hydrate solutions. Merck “Universal Indicator” colour changes were intended for indexing the dose received. For this purpose the following steps were followed: A stock solution of chloral hydrate was prepared with a concentration of 0.83 g per ml of triply distilled water resulting in a slightly acidic solution with a pH - 5.0-5.5. It was found preferable not to titrate to the neutral point since we found that the solution could be maintained much more stable over considerable periods of time. The indicator
at normal room temperatures of about 18-24% and in the dark. The solutions also do not appear to be overly sensitive to room light and even daylight. Ampoules with various concentrations of dose indicator solutions were exposed to daylight for various lengths of time. The results of this test are indicated in Table 2 Some preliminary tests with fast neutrons (mixed with 20-25 per cent gamma radiation) indicate that this dose indicator system might be applicable also in neutron fields. We have not yet investigated the complete mechanism of the chemical reactions which we believe are somewhat more complex than the simple chloral
TABLE 2 Preparation number
6oCo irradiation (krad.)
(2)
0 5 7.5 10 15 0
(3)
colour at this pH level was a fairly strong red if added in proportions of 0.02 volume parts per part of chloral hydrate solution. The response of the solutions to y irradiation was a gradually decreasing intensity of the red colour with increasing radiation dosages up to the point of leaving the solution entirely colourless at the maximum of its particular dose range. The various colour changes were easily detected when compared with the colour of the non-irradiated reference solution. Table 1 shows the sensitivity of the different preparations as well as the dose ranges which can be covered. The various solutions were test-irradiated in a AEC-“y-cell’ at a dose rate of 9134 rad./min & 5 per cent previously determined with the Fricke dosimeter system. Since this system was conceived originally only for one specific purpose and source type, no energy dependancy and radiation intensity effects were investigated until now. The stock solution as well as the various other diluted preparations were filled into thin-walled, thoroughly closed pharmaceutical (4 ml) ampoules and flame sealed. During a period of 4-8 weeks observable colour changes were not noticed in any ampoules if stored
Visually perceivable colour changes from red for daylight exposure of (40-170 hr) (12-35 hr) Slight fading Slight fading Slight fading Slight fading Slight fading Some slight and some complete discoloration
none none none none none none
hydrate to hydrochloric acid conversion. However, it appears that from the practical point of view most of the original aims of this project have been achieved, especially in view of the system’s simplicity, stability and extremely low cost. W. S. Moos J. NAGL J. HAIDER Dosimefry Section and Do&e&y Laboratory The InternationalAtomic Energy Agency Vienna, Austria References Chemical and calorimetric dosimetry. Proc. Symfi. on Selected Topics in Radiat. Dosimetry, pp. 315-377. IAEA (1960). HOLMN. W. and SEHESTEDK. Radiation Chemistry, Vol. 1, 9. 568. Advance in Chemistry Series No. 81, American Chemical Service, Washington (1968). CHADWICK K. H. Atompraxis 15, 181 (1969). Dvoa~xx I., ZEC U., ANIC A. and RANOOAJEC F. Proc. Symp. on Solid State and Chhcal Radiat. Dosimetry in Med. Biol., pp. 273-280. IAEA (1967).
A Simple
and Radiation
Inexpensive Chemical Dose Indicator *
(Receiud30 October 1969) CHEMICALdosimeterst14) with suitable ranges and accuracy have found a limited acceptance in a wide area of irradiation services. However, in some particular instances of irradiation procedures a less sophisticated device such as a simple “go-no go” type dose indicator would suffice. A particular example for the need of such a device was presented to us in connection with the “Mediterranean Fruit Fly” eradication programme conducted by various countries on cooperation with the Joint Division of Atomic Energy in Food and Agriculture and the International Atomic Energy Agency. This and some similar eradication programmes of other insect
infested area. Sterilization of the fruit flies is achieved by irradiation with about 8000 rad. rt 15 per cent from a s%o y ray source. Serious consequences could entail if the dose application should be insufficient or if irradiation is accidentally omitted. Millions and millions of fertile flies would then be added to the already excessive insect pest population. Another example of the usefulness of such a device is visualized in radiation effect studies on plants where irradiation is carried out in so-called “Gammagardens”. Small dose indicators such as described below can easily be attached in light tight containers to plants or even inserted into the ground without fear of damage to or loss of expensive instruments. Though only a dose indicator it would nevertheless allow the investigators to obtain an immediately readable indication of the radiation status of the test objects. The low cost of the system makes it particularly attractive for developing countries involved in studies for increasing crop production.
TABLE 1
Preparation number
Proportions of stock solution of chIoral* hydrate solution (ml)
(1) (2) (3)
1 1 1
HsC
Indicator solution
Dose range (krad.)
visually distinguishable dose intervals (kt=U
2 1 0
o-02 0.02 0.02
O-2.5 O-15.0 O-30.0
0.3-0.5 25-5-O 10*0-15~0
Distilled
* Concentrated chloralhydrate solution 0.83 g/ml HsO. pests make use of the so-called “irradiation induced sterile male fly” technique. These insects are irradiated to the extent that their reproductive capabilities are extinct, after emerging from the pupae stage but are otherwise undistinguishable in viability and behaviour from their normal counterparts. After release they compete with normal males in the environment but their mating results only in non-viable offsprings and consequently this particular insect population gradually becomes extinct in the
For such purposes a dosimeter was developed which fulfilled the following requirements. (1) Instant and positive indication that irradiation within the required dose range has been applied to the insects or plants. (2) The dosimeter must be exposed simultaneously with the objects to the radiation. (3) The dosimeter system should be easy to handle by lay people. The system should he cheap and simple to produce in large quantities of the throw-away type. *This work was performed in the Dosimetry (4) The dosimeter system should have a reasonable Section and Dosimetry Laboratory of the International shelf and storage lift and should not be very sensitive Atomic Energy Agency, Vienna, Austria. to climatic influences. 177
L&m
178 Methods
to the editors
and Results
The described dose indicator device made use of the radiation induced cbangea in chloral hydrate solutions. Merck “Universal Indicator” colour changes were intended for indexing the dose received. For this purpose the following steps were followed: A stock solution of chloral hydrate was prepared with a concentration of 0.83 g per ml of triply distilled water resulting in a slightly acidic solution with a pH - 5.0-5.5. It was found preferable not to titrate to the neutral point since we found that the solution could be maintained much more stable over considerable periods of time. The indicator
at normal room temperatures of about 18-24% and in the dark. The solutions also do not appear to be overly sensitive to room light and even daylight. Ampoules with various concentrations of dose indicator solutions were exposed to daylight for various lengths of time. The results of this test are indicated in Table 2 Some preliminary tests with fast neutrons (mixed with 20-25 per cent gamma radiation) indicate that this dose indicator system might be applicable also in neutron fields. We have not yet investigated the complete mechanism of the chemical reactions which we believe are somewhat more complex than the simple chloral
TABLE 2 Preparation number
6oCo irradiation (krad.)
(2)
0 5 7.5 10 15 0
(3)
colour at this pH level was a fairly strong red if added in proportions of 0.02 volume parts per part of chloral hydrate solution. The response of the solutions to y irradiation was a gradually decreasing intensity of the red colour with increasing radiation dosages up to the point of leaving the solution entirely colourless at the maximum of its particular dose range. The various colour changes were easily detected when compared with the colour of the non-irradiated reference solution. Table 1 shows the sensitivity of the different preparations as well as the dose ranges which can be covered. The various solutions were test-irradiated in a AEC-“y-cell’ at a dose rate of 9134 rad./min & 5 per cent previously determined with the Fricke dosimeter system. Since this system was conceived originally only for one specific purpose and source type, no energy dependancy and radiation intensity effects were investigated until now. The stock solution as well as the various other diluted preparations were filled into thin-walled, thoroughly closed pharmaceutical (4 ml) ampoules and flame sealed. During a period of 4-8 weeks observable colour changes were not noticed in any ampoules if stored
Visually perceivable colour changes from red for daylight exposure of (40-170 hr) (12-35 hr) Slight fading Slight fading Slight fading Slight fading Slight fading Some slight and some complete discoloration
none none none none none none
hydrate to hydrochloric acid conversion. However, it appears that from the practical point of view most of the original aims of this project have been achieved, especially in view of the system’s simplicity, stability and extremely low cost. W. S. Moos J. NAGL J. HAIDER Dosimefry Section and Do&e&y Laboratory The InternationalAtomic Energy Agency Vienna, Austria References Chemical and calorimetric dosimetry. Proc. Symfi. on Selected Topics in Radiat. Dosimetry, pp. 315-377. IAEA (1960). HOLMN. W. and SEHESTEDK. Radiation Chemistry, Vol. 1, 9. 568. Advance in Chemistry Series No. 81, American Chemical Service, Washington (1968). CHADWICK K. H. Atompraxis 15, 181 (1969). Dvoa~xx I., ZEC U., ANIC A. and RANOOAJEC F. Proc. Symp. on Solid State and Chhcal Radiat. Dosimetry in Med. Biol., pp. 273-280. IAEA (1967).