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Journal Articles

Study on loss-of-cooling and loss-of-coolant accidents in spent fuel pool, 5; Investigation of cooling effects of SFP spray and alternate water injection with MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

In this study, accident progression analyses in the SFP were performed to investigate cooling effects of the SFP spray and an alternate water injection in the loss-of-pool water accident with MAAP ver. 5.05 beta. Fuel cladding oxidation model which was created by JAEA based on their experimental data was selected and applied in the present calculations. In case of an assessment of SFP spray effects, decay heat, spray fraction going into the fuel assembly, spray droplet diameter, spray start time were selected as analytical parameters. When the SFP spray of 12.5 kg/s (200 GPM) starts 4 hours after the onset of the accident against the spent fuels with 4 months cooling and if the spray fraction going into the fuel assembly is greater than 30%, the maximum cladding temperature can be maintained under 727$$^{circ}$$C (1000 K), resulting in avoiding the cladding failure.

Journal Articles

Evaluation of the effect of spent fuel layout on SFP cooling with MAAP5.04

Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 3 Pages, 2018/11

After the accident of Fukushima-unit 1 Nuclear Power Plant, Japanese utilities are newly requested by regulatory body to take prompt measures to enhance the safety of spent fuel pool. The most important objective of this new Japanese standards of regulation is keeping a water level in a Spent Fuel Pool (SFP) under any situations in order to prevent fuel failures due to increase of fuel temperature and to avoid the occurrence of re-criticality accidents. The utilities are considered to install several kinds of safety measures for SFP. For example, a spray injection and an alternate water injection to keep pool water level, and a spent fuel layout, such as 1 by 4, 1 by 8, checkerboard to enhance cooling of the spent fuel in SFP. The objective of the present study is to investigate the effect of spent fuel layout on SFP cooling with MAAP5.04.

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 4; Loss of coolant accident analysis by MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Soga, Shota*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

We conducted the transient analysis for the phenomenon of loss of coolant in Spent Fuel Pool by Severe Accident code MAAP version 5.03 and evaluated quantitatively the influence of initial water level and decay heat on failure time and hydrogen generation of fuel cladding.

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 11; Evaluation of cooling characteristics of SFP spray and alternative water injection with MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Soga, Shota*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

Using the severe accident code MAAP5.03, simulation of the loss of cooling function accident in spent fuel pool was conducted and cooling performance of the emergency cooling systems such as spray or water inlet was evaluated.

Oral presentation

Study on improvement of safety for accident conditions in spent fuel pool, 26; Characteristics evaluation of fuel cladding oxidation model with MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

Oxidation models in dry air, in steam, and in mixture of air and steam, were previously proposed by JAEA. These oxidation models were introduced in the severe accident code MAAP, and applied for spent fuel pool accident analyses. The comparison of the analytical results with different oxidation model were conducted in this study.

Oral presentation

Benchmark analysis of SFP spray cooling test with MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki; Nagatake, Taku

no journal, , 

In order to validate a spray cooling model for spent fuel pool (SFP) in the severe accident code "MAAP", benchmark analysis of SFP spray cooling tests was conducted with MAAP ver. 5.04. In a current spray cooling model in MAAP code, spray water entered into a fuel assembly flows down uniformly on the surface of fuel pins and fuel racks in the form of liquid film and cools the fuel pin from its top to the bottom. As a result, the current MAAP model causes effective cooling and leads to the tendency of overestimation of spray cooling rate comparing to the measured data.

Oral presentation

Evaluation of alternate water injection cooling for accident conditions in spent fuel pool using MAAP code

Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki

no journal, , 

After the accident in Fukushima-Daiichi Nuclear Power Plants in 2011, deployment of spray and substitutional water inlet systems for cooling the spent fuels are recommended as safety measures against spent fuel pool (SFP) accident. In this work, analyses on an hypothetical accident which occurred by simultaneous lost of cooling ability and leaking of cooling water in SFP were conducted by using the severe accident code MAAP. For the counter measure optimization, water inlet condition to avoid cladding rupture was investigated.

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