Ishigami, Tsutomu; Shimada, Taro; Seki, Masaya; Mukai, Masayuki
JAEA-Data/Code 2015-019, 122 Pages, 2015/12
In ensuring compliance with the criterion of site release as the final stage of termination of decommissioning of nuclear facilities, it is supposed to confirm the radioactivity concentration obtained by measurement in the site is less than or equal to the concentration corresponding to the criterion. It is needed to estimate the distribution and mean of radioactivity concentration in the evaluation unit using a number of measured data. It is further needed to compare the estimated result with the concentration corresponding to the criterion of site release and to decide if the evaluation unit should comply with the criterion. The estimated result exhibits uncertainty depending on the number of measurement points, which results in a certain probability of the occurrence of decision error according to the uncertainty. It is important to decide the number of measurement points required by revealing a relationship of the error probability to the number of measurement points for site security. We have developed the ESRAD2 (Estimation of Spatial RadioActivity Distribution program version 2), which is an extended version of the existing ESRAD, for estimating the mean of radioactivity concentration and calculating the number of measurement points required according to the error probability. This report describes a method for ensuring compliance with the criterion of site release, structure and functions, input file format, output examples, execution method of ESRAD2, and sample run with ESRAD2.
Ishigami, Tsutomu; Shimada, Taro
Journal of Nuclear Science and Technology, 52(9), p.1186 - 1204, 2015/09
In the field of decommissioning of nuclear facilities, a reliable method for ensuring compliance with the criterion of site release is an important technical issue to be resolved in Japan. Considering that kriging can consider the spatial correlation of radioactivity concentrations, we propose a method of applying kriging to ensure compliance with the site release criterion. Estimated radioactivity concentrations exhibit uncertainty, which results in a certain probability of the occurrence of decision errors regarding site release. We describe a method for calculating the uncertainty and establish a minimum number of measurement points required. We applied the proposed method and a conventional statistical method to two sample cases. It was observed that the proposed method appropriately estimated the mean radioactivity concentration and led to an efficient measurement requiring fewer measurement points relative to the conventional method when spatial correlation existed.
Ishigami, Tsutomu; Shimada, Taro
JAEA-Research 2013-048, 40 Pages, 2014/03
In the field of safety regulation system for nuclear facilities after the permanent shutdown of their operations, a verification method of site release in confirmation of decommissioning completion which is a final stage of decommissioning and its specific procedure are important technical issues. On the assumption that decision-making on site release would be made based on measurement results of radioactive concentrations of soils at tens of points, we studied a calculation method of the number of measurement points and a procedure of decision-making for site release. We derived an equation to calculate the number of measurement points that gives the minimum expected cost of site release verification in ensuring safety of the public, taking into account probabilities of decision errors, scenarios of decision-making to site release, and cost of verification. We also developed a specific procedure of decision-making for site release based on the way of scenarios of decision-making.
Ishigami, Tsutomu; Sukegawa, Takenori*; Mukai, Masayuki
JAEA-Technology 2013-027, 124 Pages, 2013/10
In order to safely and efficiently implement decommissioning of nuclear installations, it is important to beforehand predict decommissioning project management data (PMD) and to develop a decommissioning plan based on the predicted results. The PMD prediction is made with PMD evaluation equations including model parameters such as unit work activity coefficients. Although model parameter values developed so far include uncertainties, little evaluation of the uncertainties and resulted uncertainties in predicted PMD has been made. However information on the uncertainties is valuable in flexibly studying and developing a decommissioning plan. We therefore studied and evaluated uncertainties in model parameters by analyzing the JPDR decommissioning experience data. This report describes an evaluation method of the model parameter uncertainties and their evaluated results.
Shibahara, Yuji; Ishigami, Tsutomu; Morishita, Yoshitsugu; Yanagihara, Satoshi*; Arita, Yuji*
JAEA-Technology 2012-038, 72 Pages, 2013/01
To implement a decommissioning project reasonably, it is necessary and important to beforehand evaluate project management data as well as to select an optimum dismantling scenario among various scenarios postulated. Little study on the subject of selecting an optimum scenario has been carried out, and it is one of the most important subjects in terms of decision making. In FY 2009, Japan Atomic Energy Agency and University of Fukui launched the joint research of a decision making method which is important to determine a decommissioning plan. The purpose of this research is to construct a methodology for selecting an optimum dismantling scenario among various scenarios postulated based on calculated results of project management data for FUGEN. Project management data for several dismantling scenarios postulated at FUGEN were evaluated based on actual dismantling work for feedwater heater at FUGEN, and an optimum scenario was discussed using the AHP, one of Multi-Criteria Decision Analysis Method. This report describes the results of the joint research in FY 2010.
Ishigami, Tsutomu; Mukai, Masayuki; Sukegawa, Takenori; Matsubara, Takeshi*
JAEA-Data/Code 2012-023, 83 Pages, 2012/11
Verification for site release is one of procedures to confirm termination of decommissioning of nuclear installations. The verification procedure would need to confirm that the radioactive concentration at the site is lower than the criterion value by measurement. Then to efficiently perform the measurement and verification it is one of important issues how to efficiently estimate and evaluate overall spatial radioactivity distribution using a sampling method. For the efficient estimation and evaluation we have applied a Kriging technique which in the geostatistics, and have developed a computer program ESRAD (Estimation of Spatial RadioActivity Distribution). The ESRAD program is designed to support sample selection, calculate a variogram, and estimate a radioactivity distribution for the area concerned. This report describes the Kriging technique, structure and functions of ESRAD, input file format, output examples, execution procedure of ERSAR, and sample run with ESRAD.
Shibahara, Yuji; Ishigami, Tsutomu; Morishita, Yoshitsugu; Yanagihara, Satoshi; Arita, Yuji*
JAEA-Technology 2011-021, 35 Pages, 2011/07
To implement reasonable decommissioning of nuclear facilities, it is necessary and important to beforehand evaluate project management data as well as to select optimum dismantling scenario among various scenarios postulated. Little study on the subject of selecting an optimum scenario has been carried out, and it is one of the most important subjects in terms of decision making. In FY2009, Japan Atomic Energy Agency and University of Fukui launched the joint research of a decision making method which is important to determine a decommissioning plan. The purpose of the research is to construct a methodology for selecting optimum dismantling scenario among various scenarios postulated based on calculated results of project management data for Fugen. Project management data for several dismantling scenarios postulated at Fugen were evaluated based on actual dismantling work for feed water heater at Fugen, and an optimum scenario was discussed using the multi-criteria decision analysis. This report describes the results of the joint research in FY2009.
Shibahara, Yuji; Tachibana, Mitsuo; Ishigami, Tsutomu; Izumi, Masanori; Nanko, Takashi
JAEA-Technology 2010-033, 42 Pages, 2010/10
Manpower needs for the dismantling process in FUGEN 3rd/4th feedwater heater room was calculated with the evaluation system (PRODIA Code), and it was inspected whether the conventional evaluation model had applicability for FUGEN or not. It was confirmed that the conventional evaluation model for feedwater heater had no applicability. In comparison of the calculated value with the actual data, we found two difference: (1) the evaluated manpower were significantly larger than the actual data, (2) the manpower need for the dismantling of 3rd feedwater heater was twice larger than that of 4th feedwater heater, though these equipments were almost same weight. It was found that these were brought (1) by the difference in the work descriptions of dismantling between JPDR and FUGEN, and (2) by that in the cutting number between 3rd feedwater heater and 4th one. The manpower needs for the dismantling of both feedwater heaters were calculated with a new calculation equation reflecting the descriptions of dismantling, and it was found that these results showed the good agreement with the actual data.
Shibahara, Yuji; Izumi, Masanori; Nanko, Takashi; Tachibana, Mitsuo; Ishigami, Tsutomu
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.347 - 353, 2010/10
Tachibana, Mitsuo; Shiraishi, Kunio; Ishigami, Tsutomu
Nihon Genshiryoku Gakkai Wabun Rombunshi, 9(3), p.271 - 278, 2010/09
DECOST code was developed in consideration of the features and structures of nuclear facilities and the similarity of dismantling methods. DECOST code could calculate 8 items of decommissioning cost. Actual data of dismantling activities was evaluated. Unit conversion factors of general components could be classified into three kinds. The weights of components in the facility and of structures of the facility were necessary for the calculation of the manpower. Methods for evaluating weight of components and structures of the facility were studied. The weight of components in the facility was proportional to weight of structures of the facility. The weight of structures of the facility was proportional to total area of floors in the facility. Decommissioning costs of 7 nuclear facilities are calculated. Outline of DECOST code, evaluation results of unit conversion factors, evaluation method of weight of components and structures were described.
Tachibana, Mitsuo; Ishigami, Tsutomu; Satoyama, Tomonori; Yoshimori, Michiro
Proceedings of 2010 ANS Topical Meeting on Decommissioning, Decontamination and Reutilization & Technology Expo (DD&R 2010) (CD-ROM), p.341 - 344, 2010/08
The clearance level verification evaluation system (CLEVES) has been developed to execute clearance activities efficiently. The SNM which is one of programs of the CLEVES was fabricated for selecting nuclides for measurement and assessment (NMA) based on evaluation of relative importance measure (RIM: nuclide activity divided by clearance level) for nuclides. In addition, case study was carried out by using the SNM based on data concerning clearance activities for concrete generated from the JRR-3. In this report, outline of the CLEVES, a method for selecting NMAs in the SNM, and calculated results of case study are described.
Tachibana, Mitsuo; Fukushima, Tadashi*; Ishigami, Tsutomu
JAEA-Testing 2010-001, 43 Pages, 2010/07
The DENESYS has been developed to support examination of decommissioning plan aiming to use management data and experiences obtained through decommissioning of nuclear facilities effectively. In the development of the DENESYS, it is important efficiently to collect, and to analyze management data obtained from actual decommissioning of nuclear facilities. Then, collecting items of management data needed to examine decommissioning plan were extracted. And en efficient collecting method of the extracted collecting items was examined based on the JPDR decommissioning project. As a result, collecting items are work management data, waste management data. These data would be collected by suing daily work management report, waste record, and secondary record data in each JAEA site. In this report outline of collecting items and collecting method for decommissioning of nuclear facilities were described. And manual for collecting management data was introduced.
Ishigami, Tsutomu; Tachibana, Mitsuo; Yanagihara, Satoshi
Nihon Genshiryoku Gakkai Wabun Rombunshi, 9(2), p.199 - 206, 2010/06
To release some materials in considerably low radioactive concentration arising from decommissioning activities of nuclear installations, it is required to confirm that the sum of D/C is lower than the reference value by measurement and evaluation of radioactive concentration. When the radioactive concentration is evaluated by using a statistical method where samples are taken from the material, two points should be taken into account; (1) a conservative evaluation that prevents underestimation to be caused by statistical uncertainties, (2) an error that may lead to a wrong decision where the material is not released due to the conservative evaluation. This paper proposes a method to determine the number of samples required for clearance verification based on a statistical theory in a consistent manner, where uncertainties in the sum of D/C is taken into account.
Tachibana, Mitsuo; Ishigami, Tsutomu
JAEA-Data/Code 2009-019, 52 Pages, 2010/02
Clearance activities for a large amount of waste with decommissioning of nuclear reactor facilities have been planned in the JAEA. To improve efficiency of clearance activities, the CLEVES has been developed to support safe and secure clearance of wastes. Program for selection of nuclides for meas. and assessment was fabricated for selecting nuclides to be evaluated based on relative importance measure for nuclides according to contamination source or contamination property of clearance objects. In addition, case studies ware carried out by using the program based on data concerning actual clearance activities in the JAEA. As a result, it has been found to be able to select nuclides for meas. and assessment safely by the individual method which evaluates relative importance measure of each contamination source, when it is difficult to analyze evaluated activity of nuclide. In this report, outline of the program was described.
Shimada, Taro; Shiraishi, Kunio; Tachibana, Mitsuo; Ishigami, Tsutomu
JAEA-Review 2009-009, 42 Pages, 2009/07
The Japan Atomic Energy Agency (JAEA: the former Japan Atomic Energy Research Institute) has been collecting wide variety of information on decommissioning nuclear facilities by the cooperative program with US Department of Energy (DOE) since 1988. In the course of the cooperation, the cooperative program has continued under the newly established specific memorandum in the field of decontamination and decommissioning nuclear facilities since 2001 on the framework agreement of USDOE and JAERI. On the other hand, the US DOE environmental management program, which was initiated in 1989, has developed resulting in achievement of dismantlement, decontamination and cleanup of nuclear facilities mainly used for Manhattan project and demonstration of various technologies developed for this program. In the cooperative activities, information on decommissioning activities including innovated technology developments has been exchanged with CP-5 and Mound plant as designated main facilities of DOE, and with JRR-2 and the reprocessing test facility of JAERI. The experiences and technologies applied in the environmental management program are expected to contribute to planning and implementing decommissioning nuclear facilities in JAEA. This report describes the summary of the information on decommissioning activities and technology development and deployment of the environmental management program in DOE obtained through the cooperation under the specific memorandum agreement.
Tachibana, Mitsuo; Shiraishi, Kunio; Ishigami, Tsutomu; Tomii, Hiroyuki
JAEA-Technology 2008-005, 33 Pages, 2008/03
The PL measuring device was produced to apply to the clearance verification measurement and the radiation measurement for releasing controlled areas. The basic characteristic test and the actual test were confirmed using the PL measuring device. As a result of these tests, it was found that the evaluation value of radioactivity with the PL measuring device was accuracy equal with the existing measuring device. The PL measuring device has feature of the existing measuring device with a light weight and easy operability. The PL measuring device can correct the ray too. The PL measuring device is effective to the clearance verification measurement of concrete on buildings and the radiation measurement for releasing controlled areas.
Sukegawa, Takenori; Shimada, Taro; Shiraishi, Kunio; Tachibana, Mitsuo; Ishigami, Tsutomu
JAEA-Data/Code 2008-009, 57 Pages, 2008/03
We developed the RADO code system for evaluating residual radioactive inventory in decommissioning of nuclear reactor. The code system consists of computer programs which calculate macroscopic effective cross section, neutron flux, and radioactive inventory. This report describes an evaluation method of radioactive inventory, structure and functions of RADO, input and output of RADO, and sample run with RADO.
Shiraishi, Kunio; Tachibana, Mitsuo; Ishigami, Tsutomu; Tomii, Hiroyuki
JAEA-Technology 2007-057, 46 Pages, 2007/09
The method for evaluating efficiently decommissioning cost in a short time was made based on the features of various types of nuclear facilities where the feature of nuclear facilities was arranged. The evaluation method can calculate decommissioning cost using conversion factors corresponding to weight of components and structures of nuclear facilities, etc. The conversion factors were made based on the experience of the JPDR decommissioning projects in the Japan Atomic Energy Research Institute (JAERI) and of improvements of the reprocessing plant of the Japan Nuclear Cycle Development Institute (JNC). In this report, the decommissioning cost evaluation method of nuclear facilities that had been made before unification of JAERI and JNC was revaluated as a new decommissioning cost evaluation method to reasonably advance decommissioning plans of various nuclear facilities.
Shiraishi, Kunio; Sukegawa, Takenori; Ishigami, Tsutomu
JAEA-Data/Code 2005-002, 162 Pages, 2006/01
In order to efficiently develop a decommissioning plan of a nuclear facility, it is useful to develop a database containing information on decommissioning technology, cost and risk analysis results, and decommissioning projects such as the JPDR decommissioning project by collecting the information systematically. A decommissioning database has been developed by collecting decommissioning related information and analyzing it. The database provides information on not only data of decommissioning technology and decommissioning projects but also laws and safety standards for decommissioning in each country and international organizations. The database is released in a Homepage on Web and is available for use via intranet with functions of retrieval, display and printing.
Umemoto, Michitaka*; Kumagai, Yoshio*; Ishigami, Tsutomu; Muramatsu, Ken
Chiiki Anzen Gakkai Rombunshu, 7, p.341 - 350, 2005/11
no abstracts in English