Personnel monitors utilizing tissue equivalent proportional counters
In the United States, the Department of Energy has established a program to improve neutron dosimetry at facilities where a significant number of workers are exposed to fast neutrons from handling isotopic neutron sources. One facet of this program is the development of small, lightweight personnel monitors to determine dose equivalent as the workers are exposed. These instruments use small cylindrical tissue equivalent proportional counters to detect neutrons, and a microprocessor to determine absorbed dose and dose equivalent. A ''Pocket REM Meter'' has been developed containing three cylindrical tissue equivalent proportional counters 1.9-cm in diameter and 13-cm long. The instrument utilizes hybrid circuitry and a 256 channel analog to digital converter to supply signals to a CMOS microprocessor, which calculates absorbed dose and dose equivalent for neutrons and displays the results on a liquid crystal display. The instrument weighs 630 grams, is 15-cm by 7.6 cm by 20-cm in size, and operates 40 hours on a 9-volt battery. Independent measurements verified that the ''Pocket REM Meter'' is accurate within 20% for determining neutron dose equivalent when exposed to unmoderated or slightly moderated Cf-252 sources, which have been calibrated by the US National Bureau of Standards. A ''Total Dose Meter'' is being developed to measure absorbed dose and determine dose equivalent from mixed radiation fields of neutrons and gamma rays. Using a single tissue equivalent proportional counter with two amplifiers operated at different gains, it is possible to measure the wide range of event sizes from mixed fields and determine absorbed dose. Using empirical algorithms derived from exposures to monoenergetic neutrons, it is possible to determine quality factors within about 7% for neutrons with energies btween 200 keV and 7.5 MeV.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5326328
- Report Number(s):
- PNL-SA-12460; CONF-8409161-7; ON: DE86014859
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ACCURACY
ALGORITHMS
MATHEMATICAL LOGIC
MEASURING INSTRUMENTS
MONITORING
PERSONNEL MONITORING
PROPORTIONAL COUNTERS
QUALITY FACTOR
RADIATION DETECTORS
RADIATION MONITORING
TISSUE-EQUIVALENT DETECTORS