Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 3; Sensitivity analysis for the quantification of epistemic uncertainty on fragility assessment

Nishida, Akemi; Choi, B.; Itoi, Tatsuya*; Takada, Tsuyoshi*; Furuya, Osamu*; Muramatsu, Ken*

Transactions of the 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08

This study focused on uncertainty-assessment frameworks and the development of relevant software to improve the reliability of seismic probabilistic risk assessment (SPRA) for NPP and promote its further use. This research aimed at contributing to development of implementation guidelines on epistemic uncertainty. Some sensitivity analyses were performed using a three dimensional reactor-building model and a conventional evaluation model by using 3D vibration simulator for NPP of JAEA, and the results were provided to the experts for expert-opinion elicitation. The results of the sensitivity analyses were related to the uncertainty evaluation of the buildings and soil to evaluate the fragility of the equipment. In this paper, those results will be shown in comparison with a conventional evaluation model.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 2; Quantifying epistemic uncertainty in fragility assessment using expert opinions

Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Furuya, Osamu*; Muramatsu, Ken*

Transactions of the 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08

The assessment of seismic safety of nuclear power plant facilities has been performed by identifying and quantifying uncertainties in seismic probabilistic risk assessment (SPRA). For the evaluation process, all uncertainties are classified into either aleatory or epistemic uncertainty for their quantification. In this study, systematic evaluation of the epistemic uncertainty on the seismic fragility of structures and equipment is studied and implemented for a model NPP. There are two expert groups formed in this project: experts in the field of buildings and soil ground (CE experts) and experts in the field of pipe and equipment (ME experts). Along with ample results from relevant sensitivity analyses conducted, elicited opinions are carefully treated and classified into several specific areas and integrated into the form of knowledge tree technique (KTT), all of which can be utilized for future fragility estimation.

Results of whole body counting for JAEA staff members engaged in the emergency radiological monitoring for the Fukushima nuclear disaster

Takada, Chie; Kurihara, Osamu*; Kanai, Katsuta; Nakagawa, Takahiro; Tsujimura, Norio; Momose, Takumaro

NIRS-M-252, p.3 - 11, 2013/03

http://repo.nirs.go.jp/dspace/bitstream/918273645/330/1/nirs_m_252.pdf

A massive earthquake and tsunami on March 11, 2011 resulted in an enormous amount of release of radioactivity to the environment. On the day after the earthquake occurrence, Japan Atomic Energy Agency (JAEA) started emergency radiological monitoring. The measurements with whole body counter (WBC) for the staff members who had returned from Fukushima started at the end of March. The measured activity of I due to inhalation for emergency staff varied from LLD to 7 kBq, which corresponded to a range of estimated initial intakes of 1 to 60 kBq when extrapolated back to the date on which the staff started the operation in Fukushima. The measured activity of Cs and Cs were both in the ranges of LLD - 3 kBq. The range of initial intake of Cs to I was 11 when taking a median from all the measurements. The maximum committed effective dose of 0.8 mSv was recorded for a worker, a member of the 2nd monitoring team dispatched from March 13 to 14.

Cracking investigation of Monju emergency generator C unit cylinder liner; Cylinder liner soundness confirmation by a fall cause of the materials strength of the cylinder liner and the supersonic wave speed

Kobayashi, Takanori; Sakon, Miyoji; Takada, Osamu; Hatori, Masakazu; Sakamoto, Tsutomu; Sato, Toshiyuki; Kazama, Akihito*; Ishizawa, Yoshihiro*; Igawa, Katsuhisa*; Nakae, Hideo*

JAEA-Review 2011-047, 48 Pages, 2012/02

JAEA-Review-2011-047.pdf:9.58MB

I confirmed a leak of the effluent gas from cylinder part during a load examination after the check of the emergency generator C unit on December 28, 2010 of the facilities check average and confirmed crack in No.8 cylinder liner part. As a result, because it was not performed oil pressure management properly without attaching an oil pressure gauge when I removed cylinder liner about the cause, crack occurred by having been able to write excessive stress for the cylinder liner and reached damage. By a process of this investigation, a fall of the materials strength of some cylinder liner was confirmed, but because a lead ingredient got mixed with materials by a casting process at the time of the production of the cylinder liner, as for this, Widmannst tten graphite occurred, and it became clear that materials strength fell. In addition, I performed inspection by the supersonic wave velocity measurement as technique to distinguish this Widmannst tten graphite easily and confirmed that I was effective.

Practical action levels for chelation therapy in plutonium inhalation using nose swab

Kurihara, Osamu; Takada, Chie; Takasaki, Koji; Ito, Kimio; Momose, Takumaro; Miyabe, Kenjiro

Radiation Protection Dosimetry, 127(1-4), p.411 - 414, 2007/11

https://doi.org/10.1093/rpd/ncm295

Practical action levels for beginning chelation therapy to remove plutonium in the body are now under discussion in Japan since there has been no experience in administrating agents to a subject in accidental intake in Japan although a first commercial reprocessing plant is about to start operation. Recently, International Commission on Radiological Protection (ICRP) proposed some medical intervention levels for chelation therapy on ICRP Publication 96. These levels are determined based on internal dose however common monitoring methods such as lung counting or excreta analysis are not necessarily suitable in terms of both sensitivity and promptness. As an alternative, the authors paid attention to nose swabs and introduced the practical action levels.

Development of Am lung monitoring system using an imaging plate

Hirota, Masahiro*; Kurihara, Osamu; Takada, Chie; Takasaki, Koji; Momose, Takumaro; Deji, Shizuhiko*; Ito, Shigeki*; Saze, Takuya*; Nishizawa, Kunihide*

Health Physics, 93(1), p.28 - 35, 2007/07

https://doi.org/10.1097/01.HP.0000258917.88579.a3

A new Am lung monitoring system without shielding was devised by using an imaging plate system. The Lawrence Livermore National Laboratory's realistic torso phantom containing a Am lung was covered by imaging plates sealed in lightproof bags. The imaging plate system displayed Am lung images characteristic of the lung shape of the torso phantom. The imaging plate system's lower detection limits of 14 Bq for 60 min exposure and 6 Bq for 300 min were the same levels as those of the phoswich detectors and the germanium detectors placed in shielded rooms. The imagingplate system for 60 min exposure detected about 2% of the annual limit of 740 Bq for Am inhalation. A lung monitoring system using imaging plates is applicable for Am lung monitoring.

Imaging of Pu distribution in the lung

Hirota, Masahiro; Kurihara, Osamu; Takada, Chie; Takasaki, Koji; Momose, Takumaro; Deji, Shizuhiko*; Ito, Shigeki*; Saze, Takuya*; Nishizawa, Kunihide*

no journal, , 

no abstracts in English

The Development and experience of internal monitoring in JAEA Nuclear Fuel Cycle Engineering Laboratory

Kanai, Katsuta; Kurihara, Osamu; Terakado, Yoshinori*; Takada, Chie; Ito, Kimio; Momose, Takumaro

no journal, , 

In JAEA Nuclear Fuel Cycle Engineering Laboratory(JAEA-NFCEL), MOX fuel fabrication facilities and spent fuel reprocessig facilities are operated during over several ten years for the purpose of establishing the nuclear fuel cycle technology. In these facilities, we have to need to pay attention to plutonium. We present the internal monitoring technique for plutonium in JAEA-NFCEL.

Pulse neutron imaging experiments in the first year of J-PARC

Kai, Tetsuya; Harada, Masahide; Oikawa, Kenichi; Sakai, Kenji; Maekawa, Fujio; Oi, Motoki; Shinohara, Takenao; Aizawa, Kazuya; Takata, Shinichi; Arai, Masatoshi; et al.

no journal, , 

Development of imaging techniques with pulse neutrons were started using the NeutrOn Beam-line for Observation and Research Use (NOBORU) of J-PARC at December 2008. The results in the first three months, future research plans and discussions on a new imaging facility in J-PARC are shown.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 1; Program plan and objectives

Muramatsu, Ken*; Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Uchiyama, Tomoaki*; Furuya, Osamu*; Fujimoto, Shigeru*; Hirano, Mitsumasa*; Muta, Hitoshi*

no journal, , 

In this research project, study on probabilistic models and treatment of epistemic uncertainty, study on quantification of epistemic uncertainty on fragility assessment and verification of usefulness of proposed method are performed for reliability enhancement of seismic risk assessment. In this report, program plan and objectives are shown as part 1.