Measurement of environmental gamma-ray dose rate around the Nuclear Fuel Cycle Engineering Laboratories, JAEA

Mizutani, Toshiyuki; Onuma, Toshimitsu; Sugai, Masamitsu; Watanabe, Hiroki; Morisawa, Masato; Takeyasu, Masanori; Sumiya, Shuichi

doi:10.15669/pnst.1.380

Cited by 1 publication

(2 citation statements)

References 1 publication

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They are also much more effective in ascertaining causes of variation in gamma exposure rates, as they can measure gamma ray energy spectra. Japan and the Baltic-Nordic countries have chosen to use NaI(Tl) scintillation detectors to monitor gamma exposure rates for this reason [1,2]. China is also planning to use dosimeters equipped with NaI detectors for its radiation monitoring system that is currently being deployed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Gamma-ray Exposure Rate Monitoring by Energy Spectra of NaI(Tl) Scintillation detectors

Lee

2017

J Radiat Prot Res

View full text Add to dashboard Cite

Background: Nuclear facilities in South Korea have generally adopted pressurized ion chambers to measure ambient gamma ray exposure rates for monitoring the impact of radiation on the surrounding environment. The rates assessed with pressurized ion chambers do not distinguish between natural and man-made radiation, so a further step is needed to identify the cause of abnormal variation. In contrast, using NaI(Tl) scintillation detectors to detect gamma energy rates can allow an immediate assessment of the cause of variation through an analysis of the energy spectra. Against this backdrop, this study was conducted to propose a more effective way to monitor ambient gamma exposure rates. Materials and Methods:The following methods were used to analyze gamma energy spectra measured from January to November 2016 with NaI detectors installed at the Korea Atomic Energy Research Institute (KAERI) dormitory and Hanbat University. 1) Correlations of the variation of rates measured at the two locations were determined. 2) The dates, intervals, duration, and weather conditions were identified when rates increased by 5 nSv•h -1 or more. 3) Differences in the NaI spectra on normal days and days where rates spiked by 5 nSv•h -1 or more were studied. 4) An algorithm was derived for automatically calculating the net variation of the rates. Results and Discussion:The rates measured at KAERI and Hanbat University, located 12 kilometers apart, did not show a strong correlation (coefficient of determination = 0.577). Time gaps between spikes in the rates and rainfall were factors that affected the correlation. The weather conditions on days where rates went up by 5 nSv•h-1 or more featured rainfall, snowfall, or overcast, as well as an increase in peaks of the gamma rays emitted from the radon decay products of 214 Pb and 214 Bi in the spectrum. This study assumed that 214 Pb and 214 Bi exist at a radioactive equilibrium, since both have relatively short half-lives of under 30 minutes. Provided that this assumption is true and that the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from the radionuclides have proportional count rates, no man-made radiation should be present between the two energy levels. This study proved that this assumption was true by demonstrating a linear correlation between the count rates of these two gamma peaks. In conclusion, if the count rates of these two peaks detected in the gamma energy spectrum at a certain time maintain the ratio measured at a normal time, such variation can be confirmed to be caused by natural radiation. Conclusion:This study confirmed that both 214 Pb and 214 Bi have relatively short half-lives of under 30 minutes, thereby existing in a radioactive equilibrium in the atmosphere. If the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from these radionuclides have proportional count rates, no man-made radiation should exist between the two energy levels. JRPR rates in various regions. -The 1,764 keV peak count rates maintained a proportional ratio to the 352 ...

show abstract

Section: Introductionmentioning

confidence: 99%

“…The values measured by NaI(Tl) scintillation detectors have been reported to decrease when temperature rises, at the rate of -0.0068/°C. 1) In other words, if the peak value at 0°C is at channel 500, it will move to channel 432 at 20°C. Such fluctuation in the peak channels requires energy calibration for each measured spectrum.…”

Section: Introductionmentioning

confidence: 99%

Gamma-ray Exposure Rate Monitoring by Energy Spectra of NaI(Tl) Scintillation detectors

Lee

2017

J Radiat Prot Res

View full text Add to dashboard Cite

show abstract

Measurement of environmental gamma-ray dose rate around the Nuclear Fuel Cycle Engineering Laboratories, JAEA

Cited by 1 publication

References 1 publication

Gamma-ray Exposure Rate Monitoring by Energy Spectra of NaI(Tl) Scintillation detectors

Gamma-ray Exposure Rate Monitoring by Energy Spectra of NaI(Tl) Scintillation detectors

Contact Info

Product

Resources

About