Improved data analysis techniques for calculating more accurate radon and thoron exhalation rates from building interior solid walls

Sakoda, Akihiro; Ishimori, Yuu; Jin, Q.*; Iimoto, Takeshi*

Applied Radiation and Isotopes, 207, p.111180_1 - 111180_8, 2024/05

https://doi.org/10.1016/j.apradiso.2024.111180

The impacts of mathematical models and associated parameters on radon (Rn) and thoron (Rn) exhalation rates based on in-situ testing at building interior solid walls were demonstrated to improve data analysis techniques.The results showed that the heterogeneity of their activity concentrations within the measurement system was more significant for thoron than radon. The diurnal variation in indoor radon should be considered for better data quality. In conclusion, a model should be appropriately made and selected under the purposes and accuracy requirements of the exhalation test.

Dosimetry of radon progeny deposited on skin in air and thermal water

Sakoda, Akihiro; Ishimori, Yuu; Kanzaki, Norie; Tanaka, Hiroshi; Kataoka, Takahiro*; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Journal of Radiation Research (Internet), 62(4), p.634 - 644, 2021/07

https://doi.org/10.1093/jrr/rrab030

It is held that the skin dose from radon progeny is not negligibly small and that introducing cancer is a possible consequence under normal circumstances, while there are a number of uncertainties in terms of related parameters such as activity concentrations in air, target cells in skin, skin covering materials, and deposition velocities. Meanwhile, an interesting proposal emerged in that skin exposure to natural radon-rich thermal water as part of balneotherapy can produce an immune response to induce beneficial health effects. The goal of the present study was to obtain generic dose coefficients with a focus on the radon progeny deposited on the skin in air or water in relation to risk or therapeutic assessments. We thus first estimated the skin deposition velocities of radon progeny in the two media based on data from the latest human studies. Using the optimized velocities, skin dosimetry was then performed under different assumptions regarding alpha-emitting source position and target cell (i.e., basal cells or Langerhans cells). Furthermore, the impact of the radon progeny deposition on effective doses from all exposure pathways relating to "radon exposure" was assessed using various possible scenarios. It was found that in both exposure media, effective doses from radon progeny inhalation are one to four orders of magnitude higher than those from the other pathways. In addition, absorbed doses on the skin can be the highest among all pathways when the radon activity concentrations in water are two or more orders of magnitude higher than those in air.

Comparison of antioxidative effects between radon and thoron inhalation in mouse organs

Kobashi, Yusuke*; Kataoka, Takahiro*; Kanzaki, Norie; Ishida, Tsuyoshi*; Sakoda, Akihiro; Tanaka, Hiroshi; Ishimori, Yuu; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Radiation and Environmental Biophysics, 59(3), p.473 - 482, 2020/08

https://doi.org/10.1007/s00411-020-00843-0

Radon therapy has been traditionally performed globally for oxidative stress-related diseases. Many researchers have studied the beneficial effects of radon exposure in living organisms. However, the effects of thoron, a radioisotope of radon, have not been fully examined. In this study, we aimed to compare the biological effects of radon and thoron inhalation on mouse organs with a focus on oxidative stress. Male BALB/c mice were randomly divided into 15 groups: sham inhalation, radon inhalation at a dose of 500 Bq/m or 2000 Bq/m, and thoron inhalation at a dose of 500 Bq/m or 2000 Bq/m were carried out. Immediately after inhalation, mouse tissues were excised for biochemical assays. The results showed a significant increase in superoxide dismutase and total glutathione, and a significant decrease in lipid peroxide following thoron inhalation under several conditions. Additionally, similar effects were observed for different doses and inhalation times between radon and thoron. Our results suggest that thoron inhalation also exerts antioxidative effects against oxidative stress in organs. However, the inhalation conditions should be carefully analyzed because of the differences in physical characteristics between radon and thoron.

Research of the tasks on risk communication enforcement in fiscal year 2016 (Contract research)

Tanaka, Masaru*; Kawara, Osami*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Kawase, Keiichi; Tokizawa, Takayuki; Miyagawa, Hiroshi*; Ishimori, Yuu

JAEA-Research 2018-001, 98 Pages, 2018/06

JAEA-Research-2018-001.pdf:2.49MB

In the 2016 fiscal year, communication cases on general waste disposal facility construction plans in recent years were surveyed. Results suggested as follows: (1) Existing long-term relationships or agreements in local area promote local accepting. (2) An operator needs to consider alternative plans and explain reasons for the decision making to local stakeholders. (3) Even after first announcement of a new plan, an operator needs to review the plan depending on local concerns. (4) Announcement of a new plan will activate communications on local development including the site redevelopment.

Comparative effects of radon inhalation according to mouse strain and cisplatin dose in a cisplatin-induced renal damage model

Sasaoka, Kaori*; Kataoka, Takahiro*; Kanzaki, Norie; Kobashi, Yusuke*; Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori*

Pakistan Journal of Zoology, 50(3), p.1157 - 1170, 2018/06

https://doi.org/10.17582/journal.pjz/2018.50.3.1157.1170

Cisplatin (CDDP) is widely used for treating solid cancers; however, it induces nephrotoxicity caused by oxidative stress. Here, we investigated whether radon inhalation has different effects against CDDP induced renal injury in two mouse strains differing in radiosensitivity, and determined the appropriate dose of CDDP combined with radon inhalation for highly radiosensitive mice. CDDP was administered at 20 mg/kg weight to C57BL/6J and BALB/c mice after radon inhalation at 1000 Bq/m and 2000 Bq/m for 24 h. Radon inhalation had a slight positive effect against CDDP toxicity in C57BL/6J mice with respect to improved hair condition, whereas radon inhalation exacerbated CDDP-induced toxicity in BALB/c mice. When BALB/c mice were treated with a lower dose of CDDP (15 mg/kg) after 1000 Bq/m radon inhalation, the creatinine level was reduced and the superoxide dismutase content was increased. The supportive effect of radon inhalation shows its good potential as a candidate treatment to alleviate CDDP-induced renal damage.

The Annual report on the environmental monitoring around the Ningyo-toge 2016; Okayama

Ono, Takayuki; Kawasaki, Satoru; Ishimori, Yuu; Ando, Masaki

JAEA-Review 2017-043, 39 Pages, 2018/03

JAEA-Review-2017-043.pdf:1.92MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency (JAEA Ningyo-toge) performs the environmental monitoring around the Ningyo-toge and the waste rock sites according to the agreements with local governments, Okayama and Tottori prefectures. Environmental monitoring of plutonium has been also performed around the Ningyo-toge regarding the practical application study on the reprocessed uranium conversion, which was carried out from 1994 to 1999 at the Ningyo-toge. Each prefectural committee on the environmental monitoring evaluates the monitoring data annually. This report summarized the results of the environmental monitoring in Okayama prefecture in the fiscal year 2016. The results show that the levels of the radiation doses and the radioactive concentrations in the environment were within natural variations, and the committee concluded that the environmental impacts from the sites were negligible. Therefore, the site of the JAEA Ningyo-toge has been well operated, and the waste rock sites have been well maintained.

Mechanisms and modeling approaches of radon emanation for natural materials

Sakoda, Akihiro; Ishimori, Yuu

Hoken Butsuri, 52(4), p.296 - 306, 2017/12

https://doi.org/10.5453/jhps.52.296

Radon emanation means the escape of radon atoms from solid grains into pore space; it is the very first process that may lead to radon exposure in the environment. Experimental and numerical studies of radon emanation have been diligently carried out since its recognition as a carcinogen. Our previous review of the measured data showed a wide range of radon emanation fractions from natural substances, and then we discussed the effects of environmental factors such as pore water. The present paper provides an overview of the approaches and progress of radon emanation modeling that may be useful for the interpretation of measured data. Recoil and/or diffusion of radon in solid following alpha decay of radium, which underlies the mechanisms of radon emanation, have been incorporated into numerical models. In the calculation based on recoil-based emanation, radium distribution and pore size were the most important parameters, which govern the magnitudes of radon ejections from the birth grain and of radon embedding into another solid surface, respectively. The solid diffusion appeared significant only at a temperature higher than a few hundred degrees Celsius. A model is now desired to be developed that incorporates the transport process of radon atoms that are still settled in solid after alpha recoil, considering radiation damage and its resulting inner path network.

Protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice

Etani, Reo*; Kataoka, Takahiro*; Kanzaki, Norie*; Sakoda, Akihiro; Tanaka, Hiroshi; Ishimori, Yuu; Mitsunobu, Fumihiro*; Taguchi, Takehito*; Yamaoka, Kiyonori*

Journal of Radiation Research, 58(5), p.614 - 625, 2017/05

https://doi.org/10.1093/jrr/rrx021

Radon therapy using radon (Rn) gas is classified into two types of treatment: inhalation of radon gas and drinking water containing radon. Although short- or long-term intake of spa water is effective in increasing gastric mucosal blood flow, and spa water therapy is useful for treating chronic gastritis and gastric ulcer, the underlying mechanisms for and precise effects of radon protection against mucosal injury are unclear. In the present study, we examined the protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice. Mice inhaled radon at a concentration of 2000 Be/m for 24 h or were provided with hot spring water for 2 weeks. The activity density of Rn ranged from 663 Bq/l (start point of supplying) to 100 Bq/l (end point of supplying).Mice were then orally administered ethanol at three concentrations. The ulcer index (UI), an indicator of mucosal injury, increased in response to the administration of ethanol; however, treatment with either radon inhalation or hot spring water inhibited the elevation in the UI due to ethanol. Although no significant differences in antioxidative enzymes were observed between the radon-treated groups and the non-treated control groups, lipid peroxide levels were significantly lower in the stomachs of mice pre-treated with radon or hot spring water. These results suggest that hot spring water drinking and radon inhalation inhibit ethanol-induced gastric mucosal injury.

Current status of decommissioning activities at Ningyo-toge Environmental Engineering Center

Ishimori, Yuu

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

This paper illustrates the current status of decommissioning activities at four facilities in the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. (1) The Test milling facility was dismantled from 1999 to 2002. The dismantled materials are stored, and surveyed to determine the quantities of contaminants in the Dismantled materials storage facility. (2) Major equipment at the Refining and conversion facility was dismantled and removed from 2008 to 2013. About 530 t of dismantled materials were generated. Measures of other materials and equipment are taken for easier area managements. (3) A part of centrifuges in the Enrichment engineering facility was decontaminated with 5% of dilute sulfuric acid, and some of them were reused after clearance. Major equipment except centrifuges at the facility has been dismantled and removed since 2014. Dismantling activity will end in 2022. So far, about 270 t of dismantled materials were generated. (4) Centrifuges in the Uranium enrichment demonstration plant have been flushed by gas since 2002 before dismantling. Decontamination efficiencies for DOP-1 and for DOP-2 were about 91% and 99%, respectively. Further plans for dismantling of centrifuges are under review. (5) Related techniques such as measurements are also explained.

Enforcement management system for decommissioning project in Ningyo-toge Environmental Engineering Center; Results of activities in fiscal year 2015

Ema, Akira; Ishimori, Yuu

JAEA-Review 2016-034, 84 Pages, 2017/03

JAEA-Review-2016-034.pdf:8.96MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency has managed the decommissioning projects since 2013. In 2015, Enforcement Management System (EMS) was established to enforce the project management systematically. The project management based on EMS was started in 2015. This report summarized the state of management activities in FY 2015.