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Journal Articles

Frontline of R&D for decommissioning and waste disposal, 1; R&D for processing and disposal of low-level radioactive waste and closure of uranium mine

Tsuji, Tomoyuki; Sugitsue, Noritake; Sato, Fuminori; Matsushima, Ryotatsu; Kataoka, Shoji; Okada, Shota; Sasaki, Toshiki; Inoue, Junya

Nippon Genshiryoku Gakkai-Shi, 62(11), p.658 - 663, 2020/11

no abstracts in English

Journal Articles

Study on decontamination of steel surface contaminated with uranium hexafluoride by acidic electrolytic water

Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*; Sugitsue, Noritake

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 8 Pages, 2019/05

Clearance of contaminated metal is important for recycling and volume reduction of radioactive waste. Among applicable decontamination technologies, immersion method with ultrasonic cleaning is considered to be effective for metal materials having various shapes. in this study is to demonstrate decontamination of carbon steel contaminated by uranium hexafluoride to the target level for clearance (less than 0.04 Bq/cm$$^{2}$$), and minimize secondary waste. In this test, acidic electrolytic water, dilute hydrochloric acid, dilute sulfuric acid and ozone water with various pH and redox potential were used as decontamination solutions to be tested. We found that acidic electrolytic water is effective solution for decontamination of carbon steel contaminated by uranium hexafluoride. It could be decontaminate less than target level for clearance, and reduced secondary waste relatively.

JAEA Reports

Uranium and environmental research platform; Social gathering of uranium and environmental research

Nakayama, Takuya; Yagi, Naoto; Sato, Kazuhiko; Hinoda, Shingo; Nakagiri, Toshio; Morimoto, Yasuyuki; Umezawa, Katsuhiro; Sugitsue, Noritake

JAEA-Review 2018-005, 163 Pages, 2018/03

JAEA-Review-2018-005.pdf:72.95MB

The Ningyo-toge Environmental Engineering Center of JAEA has been working together with local communities for more than 60 years. Through our R&D projects on from uranium exploration to uranium enrichment as a part of the nuclear fuel cycle (i.e., front-end), we have accumulated experiences in the fields of management of uranium related technology. Taking advantage of such our potential, we will start new R&D program on "Research on Uranium and the Environment." In December 2016 we announced our new concept of the "Uranium and Environmental Research Platform" as a framework aimed at contributing to regional and international society through R&D programs (environmental research and uranium waste engineering research) that are needed to steadily carry out decommissioning of uranium handling facilities.

Journal Articles

Application of support vector machine to rapid classification of uranium waste drums using low-resolution $$gamma$$-ray spectra

Hata, Haruhi; Yokoyama, Kaoru; Ishimori, Yuu; Ohara, Yoshiyuki; Tanaka, Yoshio; Sugitsue, Noritake

Applied Radiation and Isotopes, 104, p.143 - 146, 2015/10

 Times Cited Count:4 Percentile:54.36(Chemistry, Inorganic & Nuclear)

We investigated the feasibility of using support vector machine (SVM), a computer learning method, to classify uranium waste drums as natural uranium or reprocessed uranium based on their origins. The method was trained using 12 training datasets were used and tested on 955 datasets of $$gamma$$-ray spectra obtained with NaI(Tl) scintillation detectors. The results showed that only 4 out of 955 test datasets were different from the original labels-one of them was mislabeled and the other three were misclassified by SVM. These findings suggest that SVM is an effective method to classify a large quantity of data within a short period of time. Consequently, SVM is a feasible method for supporting the scaling factor method and as a supplemental tool to check original labels.

Journal Articles

Verification of uranium 238 quantity calculated using waste assay systems

Yokoyama, Kaoru; Hata, Haruhi; Ohara, Yoshiyuki; Naganuma, Masaki; Sugitsue, Noritake

Radioisotopes, 63(12), p.559 - 566, 2014/12

The amount of $$^{238}$$U in uranium-contaminated waste drums generated in the decommissioning of nuclear facilities is evaluated using $$gamma$$ ray measurement. We used the $$gamma$$-ray measurement system made from CANBERRA: Qualitative and Quantitative (Q$$^{2}$$) Low Level Waste Assay Systems and measured the waste drum. This equipment assumes uniform distribution of the uranium radiation source. But, homogeneity is not checked with a real waste drum. Authors developed the new analysis technique which calculates the amount of uranium by correcting the influence of uneven distribution of the uranium radiation source. As a result of evaluating using the new analysis technique, the error which the radiation source uneven distribution in a drum gives to $$^{238}$$U quantitative value of this equipment has been evaluated.

JAEA Reports

Evaluation formulas of manpower needs for dismantling of equipments in uranium refining and conversion plant

Izumo, Sari; Usui, Hideo; Kubota, Shintaro; Tachibana, Mitsuo; Kawagoshi, Hiroshi; Takahashi, Nobuo; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

JAEA-Technology 2014-021, 79 Pages, 2014/07

JAEA-Technology-2014-021.pdf:22.8MB

Japan Atomic Energy Agency has developed PROject management data evaluation code for DIsmantling Activities (PRODIA) to make an efficient decommissioning for nuclear facilities. PRODIA is a source code which provides estimated value such as manpower needs, costs, etc., for dismantling by evaluation formulas according to the type of nuclear facility. Evaluation formulas of manpower needs for dismantling of equipments about reprocessed uranium conversion in Uranium Refining and Conversion Plant are developed in this report. In the result, 7 formulas for prepare process, 24 formulas for dismantling process and 8 formulas for clean-up process are derived. It is confirmed that an unified evaluation formula can be used instead of 8 formulas about dismantling process of steel equipment for uranium conversion process, and 3 types of simplified formula can be used for preparation process and clean-up process respectively.

Journal Articles

Technique for recovering uranium from sludge-like uranium-bearing wastes using hydrochloric acid

Ohashi, Yusuke; Nomura, Mitsuo; Tsunashima, Yasumichi; Ando, Shion; Sugitsue, Noritake; Ikeda, Yasuhisa*; Tanaka, Yoshio

Journal of Nuclear Science and Technology, 51(2), p.251 - 265, 2014/02

 Times Cited Count:4 Percentile:59.64(Nuclear Science & Technology)

Sludge-like uranium-bearing wastes generated from uranium refining and conversion R&D facilities are stored at the Ningyo-toge Environmental Engineering Center. We have proposed an aqueous process for recovering uranium from spent filter aid and CaF$${_2}$$ precipitate using hydrochloric acid. The distributions of the dissolved species in the sample solutions at different pH levels were calculated using the chemical equilibrium modeling system. Calculated results of fluorine contents of recovered uranium were compared with the experimental results. The fluorine content in the recovered uranium decreased as the aluminum concentration of the solution increased. On the other hand, uranium of spent filter aid was recovered selectively. The size of the particles of recovered uranium tends to decrease with increasing pH in the precipitation treatments. Also, the uranium concentration of the precipitate generated by the neutralization of the barren solution falls below 1 Bq/g.

Journal Articles

Quantitative test for radioactivity of uranium filled in waste drums using Q$$^{2}$$ low level waste assay systems

Yokoyama, Kaoru; Hata, Haruhi; Ohara, Yoshiyuki; Sugitsue, Noritake

Radioisotopes, 62(11), p.833 - 840, 2013/11

We have proposed a new theory on passive $$gamma$$ assay for $$^{238}$$U determination of uranium-contaminated waste drums. According to this theory, regardless of the inhomogeneity of waste matrix density or uranium source distribution, we can accurately determine the amount of $$^{238}$$U contained in drums nondestructively using count rates of rays of two energies (1001 keV and 766 keV) emitted from $$^{238}$$U progeny nuclide $$^{rm 234m}$$Pa. This technique is aimed final at introducing into the existing $$gamma$$ ray measuring device. In this paper, we have verified the theory using the existing $$gamma$$ ray measuring device by tests under various simulated waste drums conditions. We used the $$gamma$$-ray measurement system made from CANBERRA: Qualitative and Quantitative (Q$$^{2}$$) Low Level Waste Assay Systems. The application validity of this evaluation technique was shown.

Journal Articles

Existing status of uranium refining and conversion plant decommissioning project

Sugitsue, Noritake; Morimoto, Yasuyuki; Tokuyasu, Takashi; Tanaka, Yoshio

Nippon Genshiryoku Gakkai Wabun Rombunshi, 12(3), p.242 - 256, 2013/09

This technical report showed the situation of the dismantling of the main equipment in the radiation controlled area of a uranium refining and conversion plant. And, the dismantling which we did is the work of the beginning of a uranium refining and conversion plant decommissioning project. We started dismantling in April 2008, and finished dismantling of the main equipment in a radiation controlled area in 29 September 2011. The dismantling waste and equipment was stored in the 200 little drum. All the contamination equipment can be sealed and kept in this stage. The radioactivity inventory of a uranium refining and conversion plant does not change in this stage. However, the risk of contamination by aged deterioration of this facility became remarkable small. Moreover, we were able to get many information and experience about dismantling.

Journal Articles

Development of evaluation models of manpower needs for dismantling the dry conversion process-related equipment in Uranium Refining and Conversion Plant (URCP)

Izumo, Sari; Usui, Hideo; Tachibana, Mitsuo; Morimoto, Yasuyuki; Takahashi, Nobuo; Tokuyasu, Takashi; Tanaka, Yoshio; Sugitsue, Noritake

Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 9 Pages, 2013/09

 Times Cited Count:0 Percentile:100

Journal Articles

Analysis of dismantling activities of rotary kiln for benchmark tests

Tachibana, Mitsuo; Izumo, Sari; Sugitsue, Noritake; Park, S.-K.*

DYNATOM (Internet), 2013(4), p.31 - 35, 2013/04

JAEA has the Uranium Refining & Conversion Plant. KAERI has the Uranium Conversion Plant. These CFs have been under decommissioning after their missions completed. Each organization has been developing decommissioning engineering systems to develop effective decommissioning plans and to implement dismantling activities effectively. Therefore, benchmark tests were started in order to verify mutual decommissioning engineering systems. Each organization compared mutual decommissioning engineering system, and compared specification and dismantling procedure of the rotary kiln and management data for dismantling the rotary kiln. Management data for dismantling the rotary kiln in KAERI was calculated by using DENESYS of JAEA. This report describes results of comparisons of dismantling activities of the rotary kiln in JAEA and KAERI, and calculated results by JAEA.

Journal Articles

Separation technology of uranium using inorganic acid for sludge

Ohashi, Yusuke; Tsunashima, Yasumichi; Tanaka, Yoshio; Sugitsue, Noritake

Proceedings of 5th International Conference and Exhibition on Decommissioning Challenges; Industrial Reality and Prospects (CD-ROM), 10 Pages, 2013/04

Technologies for uranium refining and conversion for production of UF$$_{6}$$ had been developed in Ningyo-Toge environmental engineering center. As a result, a significant sludge like uranium bearing waste and adsorbent was generated. These wastes total 1500 tons. They are dissolved using hydrochloric acid and dissolved uranium is recovered as uranium peroxide. Impurities in uranium peroxide and uranium content were compared with the requirement defined by ASTM. Consequently, highly pure uranium which met the requirement was recovered at low pH. The uranium remaining in the solution was removed using chelating resin in order to decrease uranium radioactivity of the neutralized precipitate that is generated later in the process. It is confirmed that aluminum in the neutralized precipitate is recovered selectively using sodium hydroxide.

Journal Articles

Verification tests on nondestructive assay for $$^{238}$$U content in uranium-contaminated waste drums using $$gamma$$ method

Yokoyama, Kaoru; Sugitsue, Noritake; Muroi, Masayuki*; Suzuki, Yasuo*

Radioisotopes, 62(1), p.1 - 17, 2013/01

Radioactive waste generated from nuclear fuel facilities must have the acceptance criterion of disposal. Although the $$gamma$$ ray measurement technique is expected as the measurement technique, the correction for the influences of the heterogeneous waste distribution was needed. Therefore, the computational technique using the $$gamma$$ ray of two energies emitted from $$^{238}$$U progeny nuclide ($$^{rm 234m}$$Pa) was developed, and verified the validity with simulated waste. As a result, the relative error was less than 20%, and detection limit was 1.2 Bq/g.

Journal Articles

Chemical decontamination using IF$$_7$$ gas

Hata, Haruhi; Yokoyama, Kaoru; Sugitsue, Noritake

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 7 Pages, 2012/07

The uranium enrichment facilities, located at Ningyo-toge in Japan, are contaminated by uranium fluorides. There is the risk of exposing the HF gas when the equipments will be dismantled. Therefore, we performed the systematic chemical decontamination by using IF$$_7$$ gas. This paper reports the actual results of the decontamination by using IF$$_7$$ gas. The result shows that the decontamination factor is approximately 100 or more. In addition, we performed the simulation of the reactions with IF$$_7$$ gas and uranium fluorides.

Journal Articles

Analysis of dismantling activities of rotary kiln for benchmark tests

Tachibana, Mitsuo; Izumo, Sari; Sugitsue, Noritake; Park, S.-K.*

Proceedings of American Nuclear Society Embedded Topical on Decommissioning, Decontamination and Reutilization and Technology Expo (DD&R 2012) (DVD-ROM), p.107 - 110, 2012/06

JAEA has the Uranium Refining & Conversion Plant. KAERI has the Uranium Conversion Plant. These facilities have been under decommissioning after their missions completed. Each organization has been developing decommissioning engineering systems to develop effective decommissioning plans and to implement dismantling activities effectively. Therefore, benchmark tests were started in order to verify mutual decommissioning engineering systems. This report describes results of comparisons of dismantling activities of the rotary kiln in JAEA and KAERI, and calculated results by JAEA.

Journal Articles

Study on evaluation of project management data for decommissioning of uranium refining and conversion plant

Usui, Hideo; Izumo, Sari; Shibahara, Yuji; Morimoto, Yasuyuki; Tokuyasu, Takashi; Takahashi, Nobuo; Tanaka, Yoshio; Sugitsue, Noritake; Tachibana, Mitsuo

Proceedings of International Waste Management Symposia 2012 (WM 2012) (CD-ROM), 13 Pages, 2012/02

Dismantling of dry conversion facility in the uranium refining and conversion plant at Ningyo-toge began in 2008. During dismantling activities, project management data have been collected. Establishment of the calculation formula for dismantling of each kind of equipment makes it possible to evaluate manpower for dismantling the whole facility. However, it is not easy to prepare calculation formula for all kinds of equipment in the facility. Therefore, a simpler evaluation method was considered to calculate manpower based on facility characteristics. The results showed promise for evaluating dismantling manpower with respect to each chemical process. To create an effective dismantling plan, it is necessary to carefully consider use of a GH preliminarily. Thus, an evaluation method of project management data such as manpower and secondary waste generation was considered. The results showed promise for evaluating project management data of GH by using established calculation formula.

JAEA Reports

Study on efficiency of dry decontamination technique by numerical method, 3 (Joint research)

Hyakutake, Toru*; Muto, Akinori*; Sasakura, Mariko*; Minowa, Hirotsugu*; Suzuki, Kazuhiko*; Yokoyama, Kaoru; Takahashi, Nobuo; Hata, Haruhi; Sugitsue, Noritake

JAEA-Research 2011-035, 53 Pages, 2012/01

JAEA-Research-2011-035.pdf:3.13MB

System decontamination has been generally carried out with the aim of reducing the amount of radioactive waste generated and minimizing exposure to radiation released from nuclear fuel facilities. At the Ningyo-Toge Environmental Engineering Center, metal surfaces that are contaminated by uranium are dry decontaminated by using iodine heptafluoride (IF$$_{7}$$) as a system decontaminator. Only a few studies have been carried out on the decontamination efficiency, mechanism, level, etc. of dry decontamination techniques that use a decontamination gas. Therefore, the generalization of dry decontamination techniques is required. In the present study, the efficiency of a dry decontamination technique was assessed by a numerical method using decontamination data obtained at the Ningyo-Toge Environmental Engineering Center. A concrete analytical content is a depositing of uranium hexafluoride.

Journal Articles

$$gamma$$ ray measuring method for a simple determination of radioactivity of uranium in waste drums

Yokoyama, Kaoru; Sugitsue, Noritake

Radioisotopes, 60(10), p.409 - 416, 2011/10

For determining radioactive of waste drums using passive $$gamma$$ ray, we showed a new analysis method deriving the linear relation between radiation source distribution and $$gamma$$ ray count rate under the homogeneous waste density. On the other hand, there were problem applying the linear relation to the case of inhomogeneous waste density. We proposed to measure the $$gamma$$ ray count rate at the positions on spherical surface surrounding the waste drum. Intending to create the approximative homogeneous waste density state, we proposed to calculate the geometric mean of measurements. As a result, we showed a relation under the inhomogeneous waste density. The relation is represented by $$frac{1}{(ln(k/bar{R}))^{2}}$$ and $$bar{n}$$, where "$$bar{R}$$" is the geometric mean of two $$gamma$$ ray (766 keV and 1001 keV) count rates ratios. "${it k}$" is the ratio of emission rates of the two $$gamma$$ rays. "$$bar{n}$$" are the geometric mean of $$gamma$$ ray (1001 keV) count rates.

JAEA Reports

Preliminary test for elution of uranium waste; Concept and application for elution test

Hata, Haruhi; Yokoyama, Kaoru; Tsunashima, Yasumichi; Ohashi, Yusuke; Koga, Osamu; Sugitsue, Noritake

JAEA-Research 2011-022, 35 Pages, 2011/09

JAEA-Research-2011-022.pdf:2.92MB

For disposal of Very low-level radioactive Waste (VLLW) from nuclear related facilities, one of important factors for safety assessment is the characteristics of elution. As for VLLW from the nuclear power plant, concrete pit and trench disposals have been performed and the evaluation methods for the characteristics have been established. On the other hand, as for the uranium waste, the concept on how to test the elution characteristics is not shown yet. Based on these circumstances, preliminary tests have been conducted to study elution characteristics of uranium waste. The results show that the important factors for the uranium elution are how uranium exists in waste. In addition, the elution characteristics also depend on the precipitation amount on the disposal site. Therefore, to assess the elution rate from uranium waste, these factors must be considered.

Journal Articles

Systematic chemical decontamination using IF$$_7$$ gas

Hata, Haruhi; Yokoyama, Kaoru; Sugitsue, Noritake

Proceedings of 14th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2011) (CD-ROM), p.105 - 110, 2011/09

IF$$_7$$ treatment technique belongs to the system decontamination technology. It has the high performance decontamination technique for the plant that deposits the uranium intermediate fluoride, for example, UF$$_4$$, UF$$_5$$, U$$_2$$F$$_9$$, and U$$_{4}$$F$$_{17}$$, which exist in the uranium enrichment plant by the Gas Centrifuge. The characteristics of IF$$_7$$ treatment, the secondary waste is just an IF$$_5$$ and little adsorbent. In addition, this IF$$_5$$ is possible to reuse as a materials for makings new IF$$_7$$ gas. According to that IF$$_7$$ treatment is the simple method using chemical reaction, we hardly need to care about secondary reaction with the exception of the reaction with IF$$_7$$ gas and the uranium intermediate fluoride. This is very important feature when applying to a large-scale plant.

107 (Records 1-20 displayed on this page)