Effort for management of radioactive waste with unknown quality and amount

Koma, Yoshikazu; Niibori, Yuichi*

Nihon Kikai Gakkai-Shi, 122(1211), p.21 - 23, 2019/10

https://doi.org/10.1299/jsmemag.122.1211_21

International Topical Workshop on Fukushima Decommissioning Research was held in March 2019 by the Japan Society of Mechanical Engineers and the Atomic Energy Society of Japan. Result of track for waste management technologies among 5 tracks is outlined.

Impact assessment of the forest fires on Oarai Research and Development Center Waste Treatment Facility

Shimomura, Yusuke; Hanari, Akira*; Sato, Isamu*; Kitamura, Ryoichi

JAEA-Technology 2015-062, 47 Pages, 2016/03

JAEA-Technology-2015-062.pdf:1.85MB

In response to new standards for regulating waste management facilities, it was carried out impact assessment of forest fires on the waste management facilities existed in Oarai Research and Development Center of Japan Atomic Energy Agency. At first, a fire spread scenario of forest fires was assumed. The intensity of forest fires was evaluated from field surveys, forest fire evaluation models and so on. As models of forest fire intensity evaluation, Rothermel Model and Canadian Forest Fire Behavior Prediction (FBP) System were used. Impact assessment of radiant heat to the facilities was carried out, and temperature change of outer walls for the assumed forest fires was estimated. The outer wall temperature of facilities was estimated around 160C at the maximum, it was revealed that it doesn't reach allowable temperature limit. Consequently, it doesn't influence the strength of concrete. In addition, a probability of fire breach was estimated to be about 20%. This report illustrates an example of evaluation of forest fires for the new regulatory standards through impact assessment of the forest fires on the waste management facilities.

A Consideration of retrievability in geologic disposal of radioactive wastes

Sasaki, Noriaki

JNC TN8420 2001-006, 56 Pages, 2001/12

JNC-TN8420-2001-006.pdf:0.9MB

Geologic disposal cannot be implemented based only on the consensus of the engaged technical community, and needs the wide social agreement and confidence for it. This is now a common understanding in many countries. Under this kind of recognition, the concept of retrievability in geologic disposal of radioadive wastes has been rapidly interested inrecent years and has being discussed in several European countries. For example, EC has cooperated the concerted action on the retrievability of long-lived radioactive waste with the joining of nine countries, and the expert group on disposal concepts for radioactive waste (EKRA) set up by the Swiss government has presented its findings on the new concept of the long-lived radioactive waste management considering the retrievability. The OECD/NEA has also discussed on this issue and published the documents. There are some countries where the legislation requires the retrievability. This paper briefly summarizes the important findings and recommendations on the concept of retrievability, as the results of review of some interesting documents from European countries, for the purpose of reflecting to the research and development of geologic disposal in Japan.

Annual report on the effluent control of Tokai Works FY 2001

Shinohara, Kunihiko; Takeishi, Minoru; ; ; Mizutani, Tomoko

JNC TN8440 2001-019, 141 Pages, 2001/11

JNC-TN8440-2001-019.pdf:12.69MB

This report was written about the effluent control in JNC Tokai Works from 1 April 2000 to 31 March 2001. In this period, the quantities and concentrations of retroactivities in liquid waste from Tokai Works were under the discharge limits of "Safety Regulations for the Tokai Reprocessing Plant", "Safety Regulations for the Tokai Reprocessing Plant" and regulations of government.

The calculation and estimation of wastes generated by decommissioning of nuclear facilities

; ; ; Takeda, Seiichiro

JNC TN8420 2001-008, 134 Pages, 2001/07

JNC-TN8420-2001-008.pdf:4.4MB

This investigation was conducted as a part of planning the low-level radioactive waste management program (LLW management program). The aim of this investigation was contributed to compile the radioactive waste database of JNC's LLW management program. All nuclear facilities of the Tokai works and Ningyo-toge Environmental Engineering Center were investigated in this work. The wastes generated by the decomissioning of each nuclear facility were classified into radioactive waste and others (exempt waste and non-radioactive waste), and the amount of the wastes was estimated. The estimated amounts of radioactive wastes generated by decomissioning of the nuclear facilities are as follows. (1)Tokai works. The amount of waste generated by decommissioning of nuclear facilities of the Tokai works is about 1,079,100 ton. The amount of radioactive waste is about 15,400 ton. The amount of exempt waste and non-radioactive waste is about 1,063,700 ton. (2)Ningyo-toge Environmental Engineering Center. The amount of waste generated by decommissioning of nuclear facilities of Ningyo-toge Environmental Engineering Center is about 112,500 ton. The amount of radioactive waste is about 7,800 ton. The amount of exempt waste and non-radioactive waste is about 104,700 ton.

Discussion of uncertainties associated with parameters of biosphere model for safety assessment of geologieal disposal through sensitivity analysis

Kato, Tomoko; ; Suzuki, Yuji*;

JNC TN8400 2001-014, 212 Pages, 2001/03

JNC-TN8400-2001-014.pdf:19.25MB

Reference Biospheres are regarded as tools which can be used for making reasonable estimates of radiological impacts for the purposes of safety assessment of geological disposal. Moreover, those are available for reducing the uncertainties based on future human environments and lifestyles. On the other hand, it is recognised that the parameter values have some uncertainties derived from experimental or sampling errors. It is possible to estimate the impacts of these uncertainties throughout the model by sensitivity analysis. Thus for this study, to evaluate the impact of the variation of migration conditions and exposure pathways, we changed some of migration and exposure parameters in turn, which were used in the compartment model where the geosphere-biosphere interface is a river in a plain.

Measures of closing report of outside waste storage pits separate volume part II; Data collections about measurement of contamination and measurement after decontamination in outside waste storage pits

; Sukegawa, Yasuhiro*; Suzuki, Satoshi*; Yoshida, Michihiro; ; *; Miyo, Hiroaki

JNC TN8440 2000-022, 180 Pages, 2000/10

JNC-TN8440-2000-022.pdf:12.16MB

At outside waste strage pits, containers for strage of wastes corroded and were flooded, and it was confirmed on August 26, 1997. Confirmation of contamination of the pits outskirts, installation of sheets to prevent rainwater from flowing into the pits, drawing stay water were executed, promptly. Design and authorization works of the work house and waste treatment devices to take out wastes of the pits were executed too. After construction of the work house, taking out wastes of the pits started, and finished on April 10, 1998. Investigations of the inflow point of rainwater and leak of stay water were executed next. The results were reported to Science and Technology Agency (STA), adjoining authorities on December 21, 1998. After decontamination of the pits inner walls to background level of the radioactivity which included general concrete, control area was removed, and the pits were closed by concrete. Measures of closing of the pits were prepared from the middle of August, 1999, and dismantlement of unnecessary instruments started. Decontamination of the pits started from the beginning of September, 1999. The above works finished on June 30, 2000. After decontamination of the pits, STA, adjoining authorities confirmed the dircumstances. Work pouring concrete into the pits was executed three times (three levels), and finished on August 31, 2000. In addition to above, the amount of concrete poured into the pits was about 1,200 m. These data compiled the inspection of contamination in measures of closing of the pits.

None

Otagaki, Takao*; *

JNC TJ8420 2000-016, 427 Pages, 2000/03

JNC-TJ8420-2000-016.pdf:18.18MB

no abstracts in English

Physico-chemical studies on the disposal of miscellaneous radioactive waste through A single-step process (III)

Iwase, Masanori*

JNC TJ8400 2000-063, 78 Pages, 2000/03

JNC-TJ8400-2000-063.pdf:1.93MB

This study is aimed at controlling oxidation reaction of molten metal by ash in incineration systems, and at positively utilizing the oxidation reaction for decontamination of slag. In this year, in order to investigate physico-chemical properties of mixed fused salt containing alkali sulfates, with special focus on the behaviour of oxygen anion in the melts, Cu / Cu redox equilibrium experiments were carried out. Among the effect of various parameters on Cu / Cu ratio in binary and ternary alkali sulfate melts, the effect of partial pressures of oxygen and SO was mainly investigated in the study. Variation in Cu / Cu ratio were presented as the function of partial pressures of oxygen and SO, respectively. Possible thermodynamic interpretation were made on the experimental results. In addition, the dissolution of CrO in mixed alkali sulfates were also investigated as a first step to elucidate the mechanism of hot corrosion. With this investigation, an important finding was obtained that the solubility of CrO for melts with same average ionic radius, in other words, oxygen ion activity, were essentially identical under constant temperature and atmosphere.

Research on engineering procedure and models on buffer materials

Amemiya, Kiyoshi*; TRAN DUC PHI OAN*; Yamashita, Ryo*

JNC TJ8400 2000-056, 487 Pages, 2000/02

JNC-TJ8400-2000-056.pdf:16.24MB

JNC presented the 2 progressive reports on HLW disposal system. The documents impressed the importance of developing the engineering procedures and the model evaluating the thermo-hydro-mechanical phenomena in waste disposal system. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. In order to assess the full-scale system performance, the Japanese experiences of buffer mass experiments were compared with the Prototype Repository Project of SKB in Sweden. Father more, the thermo-hydro-mechanical (THM) code named TRAMES was validated at the international co-research programs of DECOVALEX II.