RELAP5/MOD3.2 sensitivity analysis using OECD/NEA ROSA-2 project 17% cold leg intermediate-break LOCA test data

Takeda, Takeshi; Watanabe, Tadashi; Maruyama, Yu; Nakamura, Hideo

NEA/CSNI/R(2013)8/PART2 (Internet), p.173 - 183, 2013/12

https://www.oecd-nea.org/nsd/docs/2013/csni-r2013-8-part2.pdf#page=175

An experiment simulating a PWR cold leg IBLOCA with 17% break at cold leg was conducted. The post-test analysis by RELAP5/MOD3.2.1.2 code revealed that cladding surface temperature was underpredicted due to later major core uncovery. The post-test analysis conditions were considered as Base Case assuming the discrepancies were caused by uncertainties in the code predictability and input data. Key phenomena and related important parameters, which may affect the cladding surface temperature, were selected based on the LSTF test data analysis and post-test analysis results. Sensitivity analyses were performed by changing the parameters relevant to the key phenomena within the ranges to investigate influences of the parameters onto the cladding surface temperature. It was confirmed that both constant C of Wallis CCFL correlation at the core exit and inter-phase drag in the core are more sensitive to the cladding surface temperature.

Insights from review and analysis of the Fukushima Dai-ichi accident

Hirano, Masashi; Yonomoto, Taisuke; Ishigaki, Masahiro; Watanabe, Norio; Maruyama, Yu; Shibamoto, Yasuteru; Watanabe, Tadashi; Moriyama, Kiyofumi

Journal of Nuclear Science and Technology, 49(1), p.1 - 17, 2012/01

https://doi.org/10.1080/18811248.2011.636538

An unprecedented earthquake and tsunami struck the Fukushima Dai-ichi Nuclear Power Plants on 11 March 2011. Although extensive efforts have been continuing on investigations into the causes and consequences of the accident, and the Japanese Government has presented a comprehensive report on the accident in the IAEA Ministerial Conference held in June 2011, there is still much to be clarified on what happened during the accident and why. This article aims at identifying what should be clarified further about the progression of the accident at Units 1-3 through the review and analysis of information released from Tokyo Electric Power Company and government authorities. It also discusses the safety issues raised by the accident based on the insights gained, in order to contribute to establishing a new framework that pursues continuous improvement toward the highest standards of safety that can reasonably be achieved.

Neutron-coupled thermal hydraulic calculation of BWR under seismic acceleration

Satou, Akira; Watanabe, Tadashi; Maruyama, Yu; Nakamura, Hideo

Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive), 5 Pages, 2010/10

In the BWR subjected to an earthquake, the oscillating acceleration attribute to the seismic wave may cause the variation of the coolant flow rate and void fraction in the core, which might result in the core instability due to the void-reactivity feedback. Therefore, it is important to properly evaluate the effect of the seismic acceleration on the core stability from a viewpoint of plant integrity estimation. In the present study the numerical code analyzing the behavior of nuclear power plant under the seismic acceleration is developed based on the 3-D neutron-coupled thermal hydraulic code, TRAC/SKETCH. The coolant flow is simulated with introducing the acceleration attributed to the earthquake into the motion equation of the flow as external force terms. The analyses are performed on a real BWR4-type nuclear power plant with the sinusoidal acceleration and the acceleration obtained from the response analysis to an actual earthquake. The behaviors of the core and coolant are calculated in the various parameters of acceleration. The effects of the frequency, amplitude and direction of the oscillating acceleration are discussed.

Draft of standard for graphite core components in High Temperature Gas-cooled Reactor

Shibata, Taiju; Eto, Motokuni*; Kunimoto, Eiji*; Shiozawa, Shusaku; Sawa, Kazuhiro; Oku, Tatsuo*; Maruyama, Tadashi*

JAEA-Research 2009-042, 119 Pages, 2010/01

JAEA-Research-2009-042.pdf:26.28MB

For the design of the graphite components in the High Temperature Engineering Test Reactor (HTTR), the graphite structural design code for the HTTR etc. were applied. However, general standard systems for the High Temperature Gas-cooled Reactor (HTGR) have not been established yet. The authors had studied on the technical issues which is necessary for the establishment of a general standard system for the graphite components in the HTGR. The results of the study were documented and discussed at a "Special committee on research on preparation for codes for graphite components in HTGR" at Atomic Energy Society of Japan (AESJ). As a result, "Draft of Standard for Graphite Core Components in High Temperature Gas-cooled Reactor" was established. In this draft standard, the graphite components are classified three categories (A, B and C) in the standpoints of safety functions and possibility of replacement. For the components in the each class, design standard, material and product standards, and in-service inspection and maintenance standard are determined. This draft standard is the first standard in the world which shows the concept of standard for the graphite core components in HTGR.

Neutron irradiation effect on isotopically tailored BC

Morohashi, Yuko; Maruyama, Tadashi*; Donomae, Takako; Tachi, Yoshiaki; Onose, Shoji

Journal of Nuclear Science and Technology, 45(9), p.867 - 872, 2008/09

https://doi.org/10.3327/jnst.45.867

Basic Research on Radiation Effects of Ceramics (5)

Maruyama, Tadashi*

JNC TJ4420 2004-001, 76 Pages, 2004/03

JNC-TJ4420-2004-001.pdf:15.02MB

Ion irradiation ezperiment was carried out to elucidate microstructural change of neutron-irradiated B4C. The materials used in this investigation were boron carbides made of carbothermi-reduction method. The specimens were irradiated with helium ions having 15 MeV and 100 to 200 keV, to the fluences of 110 to 210/cm at temperatures from room temperature to 1000C. After ion irradiation, the microstructure of specimens was analyzed by transmission electron microscopy (TEM). The difference in maicrostructures disappeared among different BC pellets after ion irradiations. The ion-irradiation by 15 MeV helium ions produced a radiation-induced amorphization in the matrix. A radiation-enhanced precipitation of micro-crystals which consists of Fe-rich composition was observed in the materials irradiated below 800C. High temperature helium ion irradiation created a number of He bubbles which is associated with strain fields. When irradiation temperature was increased to 1000C, extended planer bubbles were formed on the (001) plane of BC, Extremely higher helium irradiation lead to initiation of itragranular clarks. We have also carried out studies of method for measurement of isotopic content was accurately measured when recovery of boron from irradiated BC was higher than 60%. Since ICP-MS is rather cheap and easy to measure isotopic content of materials, we studied the feasibility of using ICP-MS for measurement of 10 B in BC.

Research on adsorption and desorption properties of activated charcoals (2)

Maruyama, Tadashi*; Nagatomo, Jinro*

JNC TJ2410 2003-001, 170 Pages, 2003/08

JNC-TJ2410-2003-001.pdf:6.32MB

The results of measurement showed that anomalous breakthrough curves were observed at -180C which is effect of condensation of noble gas. However, the amomalous breakthrough curves was not observed at -170C. It was shown that the activated good performances. The effect of materials propertied on the absorption and the desorption properties is summarized as follows: The longer breakthrough time and the steeper break through curves were obtained as the grain size became smaller and the specific surface area gets larger. Further studies are needed to elucidate effect on enrichment of experimental conditions by varying such as the heating rate,sweep gas velocity,and the onset tempertuer of heating

Research on adsorption and desorption properties of activated charcoals

Maruyama, Tadashi*; Nagatomo, Jinro*

JNC TJ2410 2001-030, 265 Pages, 2002/02

JNC-TJ2410-2001-030.pdf:6.1MB

no abstracts in English

Basic Research on Radiation Effects of Ceramics

Maruyama, Tadashi*

JNC TJ4420 99-004, 118 Pages, 2000/03

JNC-TJ4420-99-004.pdf:4.92MB

no abstracts in English

Effect of Fast Neutron Irradiation on the Properties of Boron Carbide Pellet

Maruyama, Tadashi; Onose, Shoji; Kaito, Takeji; Horiuchi, Hiroto

Journal of Nuclear Science and Technology, 34(10), p.1006 - 1014, 1997/10

https://doi.org/10.1080/18811248.1997.9733777

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