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Journal Articles

Current status of uranium measurements and their related techniques at JAEA Ningyo-toge

Ishimori, Yuu; Yokoyama, Kaoru*; Hayakawa, Tomoya; Hata, Haruhi; Sakoda, Akihiro; Naganuma, Masaki

Dekomisshoningu Giho, (55), p.36 - 44, 2017/03

This paper gives an outline of the current status of uranium measurements and their related techniques at the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. The JAWAS-N and the Q$$^2$$ system have been adopted to evaluate uranium contents in the wastes. About 10 g or more of uranium in a 200 $$ell$$ drum can be evaluated by these systems. The equivalent model developed to correct the evaluation results with Q$$^2$$ system is not available to less than dozens of grams of uranium in a 200 L drum. The paper illustrates the advantage of use of the improved equivalent model which evaluates uranium content from full energy peak of 1001 keV and its Compton spectrum in order to correct the inhomogeneous distribution of uranium in measuring objects. The use of model achieved the limit of uranium quantitative determination under one tenth of those of previous evaluation methods. To determine $$^{235}$$U, it was demonstrated that the shielding factor, $$X_{geometry}$$ for evaluation of 1001 keV $$gamma$$-ray is also possible to use for evaluation of 186 keV $$gamma$$-ray. The measurement systems adopting the model have been introduced to other nuclear operators in Japan. In addition, it is also examined to use for clearance. As a related technique, feasibility studies on machine learning algorithms have been performed to classify the waste drums depending on their $$gamma$$-ray spectrum.

Journal Articles

Verification of a quantitative method of uranium 238 in the radioactive waste using photon occurred by Compton effect

Yokoyama, Kaoru; Hata, Haruhi; Naganuma, Masaki; Ohara, Yoshiyuki; Ishimori, Yuu

Radioisotopes, 64(11), p.687 - 696, 2015/11

Authors developed the new analysis technique (hereinafter referred to as the equivalent model) which calculates the amount of uranium by correcting the influence of uneven distribution of the uranium. Two $$gamma$$ rays different in the shelter effect are used in the equivalent model. The $$gamma$$ rays (766 keV, 1001 keV ) released from $$^{rm 234m}$$Pa are used for uranium quantitative determination. The quantity error is decided by the $$gamma$$ ray with the small calculation rate. The way to get the high calculation rate is considered to reduce the quantity error. Many $$gamma$$ rays are scattered by the Compton effect in radioactive waste, and scattered photons occur. We applied the scattered photon with the big count rate to equivalent model. It was effective to apply the count rate of the scattered photon by the Compton effect to equivalent model.

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

Further study of measurement of performance of the NDA using Q2 system for uranium waste drum

Naganuma, Masaki; Ohara, Yoshiyuki; Miyamoto, Yasunori*; Murashita, Tatsuya*; Makita, Akinori*; Nohiro, Tetsuya*

JAEA-Technology 2014-012, 11 Pages, 2014/06

JAEA-Technology-2014-012.pdf:1.06MB

In Japan Atomic Energy Agency Ningyo-toge environmental engineering center, exploration for uranium and technical development of uranium refining, conversion and enrichment which are the front end of a nuclear fuel cycle have been performed since 1955. In 2002, we introduced Q2 low-level-waste drum measuring system which is a bulk measuring method of the passive $$gamma$$ ray. In 2007, OS2 analyzing operation system which was used in Q2, was replaced with windows system. This replacement improved the performance of the analysis of Q2. But quantified values of uranium obtained from win system did not correspond exactly to OS2 system. We considered whether the drum which was measured by OS2 system, was measured again by windows system. But it was difficult to measure these drum by win system. So in this study, we studied a calculation method for adjusting quantified values of uranium obtained by each system.

JAEA Reports

Measurement performance of the NDA using Q2 system for uranium waste drum

Ohara, Yoshiyuki; Naganuma, Masaki; Nohiro, Tetsuya*; Yoshida, Kimikazu*; Makita, Akinori*; Sakate, Mitsuo*; Irisawa, Takumi*; Murashita, Tatsuya*

JAEA-Technology 2012-048, 39 Pages, 2013/03

JAEA-Technology-2012-048.pdf:5.1MB

In Japan Atomic Energy Agency Ningyo-Toge Environmental Engineering Center, exploration for uranium and technical development of uranium refining, conversion and enrichment which are the front end of a nuclear fuel cycle have been performed since 1955. By these research and development, about 15000 radioactive waste (200 liter drum) has occurred by now. The analytical and measurement technique of the amount of uranium which are included in radioactive waste drum were very an inexperienced in those days. Therefore, measurement strict till 2002 was not able to be started. Such a situation as this, we introduced "Q2 low-level-waste drum measuring system" which is a bulk measuring method of the passive $$gamma$$ ray using a NaI scintillation detector in 2002. As a result, the total amount of uranium in a waste drum was estimated as about 20 tons.

Journal Articles

Method for removing radium from mine water

Naganuma, Masaki; Taki, Tomihiro

JAEA-Conf 2006-007, p.55 - 58, 2006/06

no abstracts in English

Oral presentation

Behavior of cesium in the soil by heating

Yokozawa, Takuma; Kobayashi, Hidekazu; Yamashita, Teruo; Nagai, Takayuki; Tokizawa, Takayuki; Naganuma, Masaki; Aoki, Katsumi

no journal, , 

no abstracts in English

Oral presentation

applied example MCNP5 on skyshine of nuclear facility

Zaima, Naoki; Naganuma, Masaki; Sakao, Ryota; Tokizawa, Takayuki

no journal, , 

In the field of safety analysis on nuclear fuel facility, conventional calculation code (QAD/G33 etc.) had been used. However some confines of codes had lead overestimation. At the chance of trial for shielding or skyshine calculation, Monte Carlo transport calculation code MCNP5 was applied. The comparison between both, error estimations, model designs, several artifices will be introduced.

Oral presentation

Applied example MCNP5 on ambient dose evaluation from nuclear facility

Zaima, Naoki; Naganuma, Masaki; Sakao, Ryota

no journal, , 

no abstracts in English

Oral presentation

A Proposal of an evaluation method in $$gamma$$ ray measurements for clearance of various decommissioning materials in forms

Ishimori, Yuu; Yokoyama, Kaoru*; Naganuma, Masaki

no journal, , 

Although the clearance of uranium was institutionalized for metals, its implementation has been actually limited only to metals with simple shapes because of problems of the measurement. The present study proposes an evaluation method in $$gamma$$ ray measurements for the clearance of various decommissioning materials in forms. The proposed method was based on the analysis technique, called "equivalent model" focusing on $$gamma$$ rays scattered by the Compton effect, developed in Ningyo-toge Environmental Engineering Center. This model was applied to the analysis of test results of simulated drums measured using a commercially-available $$gamma$$-ray measurement system. The analysis result indicated the validity of this application for the clearance level of 1Bq/g (total uranium). The presentation will describe the concept of a new evaluation method including an improvement of the measurement system.

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