Ultra-clean underground counting facility for low-level environmental samples
An underground counting facility with cleanroom environment has been designed and constructed to improve detection of low-level radioisotopes in the environment. The 3.0 m x 4.3 m x 2.4 m counting chamber is placed 14.3 m below ground, has 10.2-cm thick walls of pre-WWII naval armor plate, and is further shielded by a minimum of 1.2 m of specular hematite. The total overburden of shielding is equivalent to 31.7 m of water. Careful selection of building materials and a special air filtering system maintain a cleanroom environment with minimum contamination potential. Background improvements are noted relative to an earlier ground-level counting chamber with 30.5-cm-thick walls of pre-WWII naval armor plate. The gamma background continuum is reduced by a factor of 3 to 4 in the region of 0 to 10 MeV. A minimum of 10.2 cm of low-background lead around the detector optimizes this factor at 4 to 6. Discrete gammas from airborne natural radon daughters are eliminated by controlling the air near the detectors. Detectors constructed with low-level materials will further realize the improvements in background. A constant background is required for long counts of low-level samples, and the underground detectors are well shielded against surface operations. Performance appraisals of facility detectors include a large dual NaI(Tl) coincidence system, three smaller NaI(Tl) detectors, an HPGe well detector, and gas proportional and geiger counters. Major electronics for the detectors are located at a ground level control center to eliminate any associated backgrounds. Because an individual sample may be counted several days, uninterruptable power is used. An IBM PC/XT computer processes spectra from multichannel analyzers using custom-developed software.
- Research Organization:
- Du Pont de Nemours (E.I.) and Co., Aiken, SC (USA). Savannah River Lab.
- DOE Contract Number:
- AC09-76SR00001
- OSTI ID:
- 7025959
- Report Number(s):
- DP-MS-85-157; CONF-8610174-1; ON: DE87002657
- Resource Relation:
- Conference: 5. symposium on environmental radiochemical analysis, Harwell, UK, 1 Oct 1986; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Design and Characterization of an Extremely-Sensitive, Large-Volume Gamma-Ray Spectrometer for Environmental Samples
Correlation of Scan and Sample Measurements Using Appropriate Sample Size
Related Subjects
RADIATION MONITORING
SAMPLE PREPARATION
UNDERGROUND FACILITIES
CONSTRUCTION
DESIGN
BIOLOGICAL MATERIALS
CONTAMINATION
LOW LEVEL COUNTERS
RADIOACTIVITY
RADIOISOTOPES
ISOTOPES
MATERIALS
MEASURING INSTRUMENTS
MONITORING
RADIATION DETECTORS
510300* - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (-1989)
510200 - Environment
Terrestrial- Chemicals Monitoring & Transport- (-1989)