DETAILED DESIGN OF A FIXED PAPER ALPHA AIR MONITOR WITH LESS THAN FIFTEEN MINUTES RESPONSE TIME
The primary health physics problem at the gaseous diffusion plants where iranium isotopes are separated is that of airborne alpha-emitting uranium dust. A recently developed instrument that provides a rapid alarm if the airborne uranium dust from a release reaches hazardous levels is discussed. Prior to its development a delay of approximately five hours was required to allow natural atmospheric radioactivity to decay before long-lived alpha emitters from uranium dust could be detected. This recently developed instrument functions on the principle that when airborne dust containing natural atmospheric radon daughters is collected, the activity will increase to a quasi-equilibrium value at which time the rate of deposition will be equal to the rate of decay. The uranium dust is then observed as a rapid change from equilibrium conditions. A unique feature of the instrument is the use of a special differentiating circuit to actuate an alarm when the rate of increase of radioactivity exceeds that which can be expected from the diurnal variations in atmospheric radioactivity levels. The development model of this instrument uses a vacuum pump to draw air through a filter paper disc which collects the entrained dust particles. The alpha radiation from the dust is detected with a scintillation detector. The electron circuitry consists of amplifiers and rate circuits which provide monitored outputs proportional to both the level of radioactivity and the rate of change in this level. One circuit utilizes a special very high capacity electrolytic capacitor which was subjected to extensive testing to determine that certain leakage requirements can be met. In addition, special attention was paid to the problem of not actuating the alarm on statistical fluctuations. Twelve transistors are used in'the circuit. This monitor features small size and simplicity, and economy in fabrication, operation, and maintenance not available in other known monitor designs. It provides an alarm within 15 minutes when uranium dust concentrations exceed 2 1 x 10/sup -10//sup >/ mu c/cm/sup 3/ (three and one-half times the maximum permissible concentration for a 40-hour per week exposure). Additionally, it can be used to measure the average weekly uranium dust concentration by the removal of the filter disc and the measurement of its radiation level after an appropriate decay period. (auth)
- Research Organization:
- Oak Ridge Gaseous Diffusion Plant, Tenn.
- NSA Number:
- NSA-15-015761
- OSTI ID:
- 4038842
- Report Number(s):
- TID-12435; NE/148
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ACCIDENTS
AIR
ALARM SYSTEMS
ALPHA PARTICLES
ALPHA SOURCES
AMPLIFIERS
ATMOSPHERE
CAPACITORS
CIRCUITS
DECAY
ECONOMICS
EFFICIENCY
ELECTRIC CONDENSERS
ELECTROLYTES
ELECTRONIC EQUIPMENT
FILTERS
GASES
INSTRUMENTS
LEAKS
MEASURED VALUES
MONITORING
PAPER
PARTICLE SOURCES
PLANNING
PUMPS
QUANTITY RATIO
RADIATION DOSES
RADIOACTIVITY
RADIOISOTOPES
RADON
SAFETY
SCINTILLATION COUNTERS
STATISTICS
TRANSISTORS
URANIUM
VACUUM