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論文

In-situ detection of high-energy beta ray emitter $$^{90}$$Sr/$$^{90}$$Y inside the Fukushima Daiichi Nuclear Power Station Unit 3 reactor building using a liquid light guide Cherenkov counter

寺阪 祐太; 佐藤 優樹; 古田 禄大*; 久保 信*; 一場 雄太*

Nuclear Instruments and Methods in Physics Research A, 1070(2), p.170021_1 - 170021_9, 2025/01

https://doi.org/10.1016/j.nima.2024.170021
 被引用回数：0 パーセンタイル：0.00(Instruments & Instrumentation)

We have developed a method to directly detect $$^{90}$$Sr/$$^{90}$$Y under a high gamma ray background using a liquid light guide Cherenkov counter. Cherenkov radiation has the characteristic that the angle of radiation varies depending on the energy of the charged particles. Using this feature, we have developed a surface contamination detector capable of discriminating between 662 keV gamma rays from $$^{137}$$Cs and beta rays from $$^{90}$$Sr/$$^{90}$$Y through time-of-flight analysis of the Cherenkov radiation generated inside the liquid light guide. With this detector, we conducted a measurement test of $$^{90}$$Sr/$$^{90}$$Y inside the Fukushima Daiichi Nuclear Power Station Unit 3 reactor building and achieved the first in-situ detection of $$^{90}$$Sr/$$^{90}$$Y under a high gamma-ray background.

論文

A New application technique of a position-sensitive liquid light guide Cerenkov counter for the simultaneous position detection of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs radioactivity

寺阪 祐太; 瓜谷 章*

Nuclear Instruments and Methods in Physics Research A, 1049, p.168071_1 - 168071_7, 2023/04

https://doi.org/10.1016/j.nima.2023.168071
 被引用回数：2 パーセンタイル：59.55(Instruments & Instrumentation)

A new application of a position-sensitive liquid light guide Cerenkov counter for the simultaneous position detection of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs radioactivity in a gamma-ray-dominant environment is proposed. $$beta$$-emitting $$^{90}$$Sr/$$^{90}$$Y and $$gamma$$-emitting $$^{137}$$Cs radioactive point sources were measured using a position-sensitive liquid light guide based on the time-of-flight (TOF) method. We found a clear difference in the count rate ratio between the source position peak and reflection peak of the position histogram. Moreover, simultaneous measurements of the radioactive point sources were performed. The results suggest that the source position and activity of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs can be simultaneously determined based on the count rate ratio of the source position peak and the reflection peak.

口頭

Selective detection of $$^{90}$$Sr/$$^{90}$$Y under gamma-ray field using the liquid light guide Cerenkov counter

寺阪 祐太

no journal, , 

In this presentation, we will introduce a method for selectively detecting the $$^{90}$$Sr/$$^{90}$$Y distribution in a gamma-ray environment using a liquid light guide, which is an optical fiber with a liquid core material. This method applies the aforementioned time-of-flight analysis to the liquid light guide to determine the location of radioactive materials. Here, the Cerenkov radiation from $$^{90}$$Sr/$$^{90}$$Y is selectively detected by using the reflection at the light guide's end face, caused by the radiation energy dependence of the Cerenkov radiation angle. The Cerenkov radiation from $$^{90}$$Sr/$$^{90}$$Y is characterized by a larger emission angle and a smaller emission angle for the Cerenkov radiation from gamma-ray emitting nuclides. Therefore, the latter has a greater proportion of reflected components at the light guide's end face compared to the former. Utilizing this feature, the in-situ radioactivity distribution of $$^{90}$$Sr/$$^{90}$$Y can be detected.

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