Simulation of alpha continuous air monitor alarm response in the presence of plutonium

Conference · Sat Jul 01 00:00:00 EDT 1989

OSTI ID:6606372

Brown, R C ^[1]; Fleming, D M; Nichols, L L ^[2]

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1. Westinghouse Hanford Co., Richland, WA (USA)
2. Pacific Northwest Lab., Richland, WA (USA)

The presence of radon and thoron daughters causes interference in the plutonium channel of alpha continuous air monitors used to detect airborne plutonium. Single-channel alpha energy spectroscopy is used to minimize this effect, and additional compensation is provided by electronically subtracting a constant fraction of the count rate appearing in the higher energy radon window'' from the count rate appearing in the plutonium window. The standard deviation of the resulting net count rate is nonzero. The probability of falsely reporting the presence of plutonium when in fact none is present (Type I error) is influenced by this nonzero standard deviation and becomes unacceptably high if the alarm setpoint is too low. These conditions were used to simulate the response of an alpha continuous air monitors to radon interference using a Monte Carlo simulation. Radon and thoron daughter concentrations measured during a one-week period were used. These measurements indicated the diurnal variations of over two decades in radon and thoron daughter response as well as a longer in-growth of {sup 212}Pb and subsequent daughter transitions were present. The response of the logarithmic count rate meter was also simulated to preserve the normally observed fluctuations. The simulations include response of the alpha CAM with the observed radon and thoron daughter contributions with and without plutonium present. Information obtained included the following as a function of alarm setpoint: number of Type I alarms and the time required to provide a true alarm after initiation of simulated plutonium releases. 3 refs., 8 figs., 1 tab.

• Research Organization: Westinghouse Hanford Co., Richland, WA (USA)
• Sponsoring Organization: DOE/EH
• DOE Contract Number: AC06-87RL10930
• OSTI ID: 6606372
• Report Number(s): WHC-SA-0483; CONF-8907215--1; ON: DE90017727
• Country of Publication: United States
• Language: English

Related Subjects

440101 -- Radiation Instrumentation-- General Detectors or Monitors & Radiometric Instruments
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
54 ENVIRONMENTAL SCIENCES
540130* -- Environment
Atmospheric-- Radioactive Materials Monitoring & Transport-- (1990-)
ACTINIDE COMPOUNDS
AEROSOLS
AIR
AIR SAMPLERS
ALARM SYSTEMS
ALPHA DECAY RADIOISOTOPES
BACKGROUND RADIATION
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALIBRATION STANDARDS
COLLOIDS
COMPUTERIZED SIMULATION
CORRECTIONS
DAILY VARIATIONS
DAUGHTER PRODUCTS
DISPERSIONS
ECOLOGICAL CONCENTRATION
EQUIPMENT
EVALUATION
EVEN-EVEN NUCLEI
FLUIDS
GASES
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
INTERFERENCE
ISOTOPES
LEAD 212
LEAD ISOTOPES
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MONITORING
MONITORS
MONTE CARLO METHOD
NUCLEI
PLUTONIUM COMPOUNDS
RADIATION DETECTORS
RADIATION MONITORING
RADIATION MONITORS
RADIATIONS
RADIOACTIVE AEROSOLS
RADIOECOLOGICAL CONCENTRATION
RADIOISOTOPES
RADON 220
RADON ISOTOPES
SAMPLERS
SECONDS LIVING RADIOISOTOPES
SIMULATION
SOLS
STANDARDS
TRANSURANIUM COMPOUNDS
VARIATIONS