Real-time {sup 90}Sr Counter
- Graduate School of Science, Chiba University, Chiba, (Japan)
Radioisotopes have been emitted around Japan due to a nuclear accident at the Fukushima Daiichi nuclear power station in March 2011. A problem is the contaminated water including the atomic nucleus which relatively has a long half- life time and soluble such as {sup 90}Sr, {sup 137}Cs. Internal exposures by {sup 90}Sr are more dangerous than {sup 137}Cs's because Sr has effective half-life time of 18 years and property of accumulation in a born. We have developed real-time {sup 90}Sr counter which is sensitive beta-ray of maximum kinematic energy of 2.28 MeV from {sup 90}Sr and insensitive of beta-ray of maximum kinematic energy of 1.17 MeV and gamma-ray from {sup 90}Sr by Cherenkov detection. This counter composes of Cerenkov counter, trigger scintillation counter and veto counter. Silica aerogel for Cherenkov counter can obtain refractive index between 1.017 and 1.049 easily. And wavelength shifting fiber (WLSF) is used as a light guide for extending effective area and producing lower cost. A mechanism of the identification of {sup 90}Sr is explained in following. In case of {sup 90}Sr, when the trigger counter reacts on the beta-ray from {sup 90}Sr, aerogel emits the Cherenkov light and WLSF reacts and read the Cherenkov light. On the other hand, in case of {sup 137}Cs, the trigger counter reacts on the beta-ray, aerogel stops the beta- ray and Cherenkov light is not emitted. Therefore, aerogel has a function as a radiator and shielding material. the gamma-ray is not reacted on the lower density detector. Cosmic rays would be also reacted by the veto counter. A prototype counter whose the effective area is 30 cm x 10 cm was obtained (2.0±1.2){sup 3} of mis-identification as {sup 137}Cs/{sup 90}Sr. Detection limit in the surface contamination inspection depends on measurement time and effective area mainly. The sensitivity of wide range, 10{sup -2} - 10{sup 4} Bq/cm{sup 2}, is obtained by adjustment of detection level in circuit of this counter. A lower radioactive sample (< 10{sup -2} Bq/cm{sup 2}) allows be detected significantly by heating treatment to evaporate water shielding the beta-rays. (authors)
- Research Organization:
- Institute of Electrical and Electronics Engineers - IEEE, 3 Park Avenue, 17th Floor, New York, N.Y. 10016-5997 (United States)
- OSTI ID:
- 22531274
- Report Number(s):
- ANIMMA-2015-IO-222; TRN: US16V0307102215
- Resource Relation:
- Conference: ANIMMA 2015: 4. International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, Lisboa (Portugal), 20-24 Apr 2015; Other Information: Country of input: France; 7 Refs.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BIOLOGICAL HALF-LIFE
BUILDUP
CESIUM 137
CHERENKOV COUNTERS
FUKUSHIMA DAIICHI NUCLEAR POWER STATION
GAMMA RADIATION
HALF-LIFE
MEV RANGE
OPTICAL FIBERS
RADIATION ACCIDENTS
RADIATORS
REACTOR ACCIDENTS
REFRACTIVE INDEX
SCINTILLATION COUNTERS
SENSITIVITY
SHIELDING MATERIALS
STRONTIUM 90
SURFACE CONTAMINATION
VISIBLE RADIATION
WATER