FIG. 1. 
Cambridge, Mass. 
Arrangement for removing radiation-induced darken- 
ing of glasses by heating 
Glass Dosimetry 
By S. DAVISON, S. A. GOLDBLITH, and B. E. PROCTOR 
Department of Food Technology * 
Massachusetts Institute of Technology 
Here's a thorough study of silver-phosphate glass as a dosimeter: the effects of 
storage temperature, how postirradiation heat treatment stabilizes fading, the 
effect of freezing temperatures during irradiation, and other parameters 
PRODUCTION-LINE STERILIZATION 
of foods, drugs, and biological’ mate- 
rials by ionizing radiations grows in- 
creasingly probable as technical prob- 
lems are solved and the number of 
applications increases. It is a practi- 
cal and legal necessity to measure 
doses accurately in these radiation 
processes, but most of the existing 
dosimetric systems, which are based on 
ionization or calorimetric principles, 
do not easily lend themselves to rapid, 
routine, and accurate measurements. 
Investigations at the Naval Research 
Laboratory by Schulman and associ- 
ates (1, 2, 3, 12) and here at MIT (4, 
13) have indicated that the silver- 
activated phosphate glass, originally 
developed at NRL (4, 6, 7) to measure 
low personnel doses, has good poten- 
tialities for measuring high doses. In 
the measurement of high doses the 
optical absorption is used rather than 
the fluorescence properties used at the 
low doses. 
The use of glass as a dosimeter has 
several advantages that make it espe- 
cially attractive for use in this field. 
These include chemical inertness, ri- 
* This paper summarizes work done by 
the Department of Food Technology, Mass. 
Inst. of Technology, on A.E.C. Contract 
AT(30-1)-1164 (4, 13). 
gidity, insolubility, small size, and per- 
manence. A thorough investigation 
of those properties of silver-activated 
phosphate glass of importance in high- 
level dosimetry is reported here. 
Apparatus and Methods 
The glass used was Corning #9761. 
The composition is that originally speci- 
fied at NRL, namely, 50% Al(POs)s, 
25% Ba(POs)2, and 25% KPOs, with 
about 8% AgPO; added. 
Sources. The source of gamma ra- 
diation used was a multicurie Co* 
source (10) with a dose rate of ~1,400 
rep/min. The doses used were based 
upon experiments and calculations em- 
ploying physical dosimetric methods 
and the ferrous-ferric dosimeter (10). 
The specific yield of the ferrous-ferric 
o Refrig. storage 2-4°C 
@ 20°C storage 
6 8 igo Is! OU 2 
Time After End of Irradiation (hours) 
__ 100 
Ls 
se 90 
2s 
wo 
me SO Room-temp. storage 23-30°C 
iS 70 | ® 37°C storage 
25 Q 55°C storage 
e260 
a 
\ 2°34 6 84 2 34 
FIG. 2. 
glasses not given heat treatment 
if 
2 now oe 
oo OO 
Absorbanc 
Index (cm- 
OMS suOMISH20;y 2 
Minutes of Heat 
a4 
6 810 
Storage Time at Room Temperature (hours) 
Effect of storage temperature on irradiated silver-activated phosphate 
20 3040 60 80100 200 
FIG. 3. Effect of heating temperature on irradiated glasses stored at room 
temperatures 
