Long-Term Monitoring of Tritium Concentration in Environmental Water Samples Collected at Tono Area, Japan

Iwata

Kato

et al. 2019

IJERPH

Self Cite

The deuterium plasma experiment was started using the Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS) in March 2017 to investigate high-temperature plasma physics and the hydrogen isotope effects towards the realization of fusion energy. In order to clarify any experimental impacts on precipitation, precipitation has been collected at the NIFS site since November 2013 as a means to assess the relationship between isotope composition and chemical species in precipitation containing tritium. The tritium concentration ranged from 0.10 to 0.61 Bq L−1 and was high in spring and low in summer. The stable isotope composition and the chemical species were unchanged before and after the deuterium plasma experiment. Additionally, the tritium concentration after starting the deuterium plasma experiment was within three sigma of the average tritium concentration before the deuterium plasma experiment. These results suggested that there was no impact by tritium on the environment surrounding the fusion test facility.

Section: Introductionmentioning

confidence: 99%

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

Iwata

Kato

et al. 2019

IJERPH

Self Cite

“…As for the environmental assessment, the distribution of environmental radiation at the NIFS site [2], including tritium concentration in environmental water samples (river water, pond water, well water, tap water, and rainwater) collected at the Tono area [3], free water tritium and organically bound tritium in pine needle samples collected at the NIFS site and nearby [4,5] and tritium concentrations of HTO, HT, and CH 3 T in the atmosphere [4,6], are monitored prior to running the deuterium plasma ex- periment. However, from the viewpoint of radiation management in the control area, the following instruments for the management and control of tritium have been prepared: a portable-type tritium recovery apparatus, an expiratory water-trapping apparatus for internal tritium exposure measurement, a room gas monitor using an ionization chamber, an EDS for the LHD exhaust gas [7,8], a largevolume ionization chamber and active tritium samplers in the stack [9], etc.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of Tritium Concentration by Simplified Active Sampler in a Fusion Test Facility

Plasma and Fusion Research

Yamamoto

Iwata

2018

Self Cite

From the viewpoints of radiation management and public acceptance, the monitoring of tritium concentration in the stack is one of the key issues for the deuterium plasma experiment in the Large Helical Device (LHD). Since 2012, an active tritium sampler was employed in the stack to monitor the background levels of tritium and discriminate between its chemical forms. However, the operation procedure became complicated, so we developed a simplified active tritium sampler to reduce the work after sampling. In this sampler system, there was no discrimination between tritium chemical forms, instead, all tritium chemical forms were collected in one process. To verify the performance of the simplified active tritium sampler, tritium concentration data was compared with the existing tritium active sampler and environmental tritium data at the NIFS site. The results revealed a correlation between these tritium data. Therefore, the simplified active tritium sampler was applied in the stack with a primary monitoring system for the deuterium plasma experiment in the LHD.

“…KEY WORDS: soil, pine needle, 137 Cs, 7 Be, 40 K, radioactivity, environmental monitoring, Toki, Gifu Prefecture.…”

mentioning

confidence: 99%

“…limits in7 Be,54 Mn,59 Fe,58 Co,60 Co,134 Cs,137 Cs and 40 K.Detection limits of pine needles [Bq/kg] 5.70-19.5 0.63-1.15 1.50-2.46 0.67-1.30 0.87-1.41 0.74-1.29 0.63-1.74 8.83-18.0 Detection limits of soil [Bq/kg] 2.78-13.3 0.37-1.25 0.83-3.64 0.35-1.42 0.42-1.20 0.34-0.97 0.38-2.46 4.08-10.7…”

mentioning

confidence: 99%

核融合科学研究所における松葉及び土壌中の環境放射性物質のモニタリング

Nakada

Kato

et al. 2021

Jpn. J. Health Phys.

Self Cite

NIFS), the environmental radioactivity in soil and pine needles were measured from 2014 to 2019 as a part of the monitoring activities for deuterium plasma experiments using Large Helical Device (LHD). Among the monitoring nuclides of 54 Mn, 59 Fe, 58 Co, 60 Co, 134 Cs, 137 Cs, 7 Be and 40 K, the nuclides of 137 Cs, 7 Be and 40 K were detected by a HPGe detector. The concentration of 40 K in soil ranged from 530 Bq/kg to 1,068 Bq/kg, which was the same level at the Tono area reported by Hosoda et al. In addition, the concentration of 40 K in pine needles ranged from 125 Bq/kg to 300 Bq/kg and a peak was observed in summer. The maximum concentrations of 7 Be on soil and pine needles were 69.4 Bq/ kg and 31.9 Bq/kg, respectively. The concentration of 7 Be on pine needles became low in summer. Although the concentration of 137 Cs on pine needles was not almost detectable, that on soil ranged from 0.56 Bq/kg to 3.69 Bq/kg. The concentrations of these nuclides remain the same level after starting the deuterium plasma experiment in LHD.