Long-Term Cooling Strategy for the Primary Containment Vessel of the Kashiwazaki-Kariwa Nuclear Power Station in a Severe Accident

2017 ◽  
Author(s):  
Satoshi Kawaguchi ◽  
Satoshi Mizuno ◽  
Yoshihiro Oyama
Keyword(s):  
Heat Exchanger ◽  
Nuclear Power Station ◽  
Nuclear Power ◽  
Heat Removal ◽  
Severe Accident ◽  
Power Station ◽  
Working Temperature ◽  
Containment Vessel ◽  
Portable Pump

This paper explains the strategy of our company (Tokyo Electric Power, TEPCO) regarding means of long-term heat removal from the primary containment vessel (PCV) of Units 6 and 7 (ABWR) of the Kashiwazaki-Kariwa Nuclear Power Station in a severe accident. If the PCV continues in a high-temperature state for a long time, the strength of the PCV concrete will decline, and the risk of being affected by an earthquake will increase. Therefore, it is crucial for safety to cool the PCV and reduce its temperature to the maximum working temperature or lower. TEPCO provides a means of cooling the reactor pressure vessel (RPV) and PCV called the alternative coolant circulation system (ACCS). This system uses the heat exchanger of the residual heat removal (RHR) system, the make up water condensate (MUWC) pump, and alternative heat exchanger vehicles. By using these measures, it is possible reduce temperature in the PCV over the long term to the maximum working temperature (design value) or less, even in severe accident scenarios such as a large LOCA + ECCS function failures + SBO (station blackout). This function has quite high reliability, but in a scenario where these measures cannot be used, expectations are placed on the filtered vent (FV). However, due to FV characteristics, it is impossible to reduce to below the saturation temperature of 100°C at atmospheric pressure using FV alone, and it will be necessary in the medium/long-term to cool the PCV while also restoring the cooling equipment. Therefore, the following restoration operation of PCV cooling and its dose evaluation were studied. (1) RPV heat removal by restoring the RHR system (2) RPV and PCV heat removal using a portable pump employing a portable heat exchanger (3) RPV and PCV heat removal using the suppression pool water clean up system (SPCU) employing portable heat exchangers (4) RPV heat removal using the clean up water system (CUW) By clarifying beforehand issues such as feasibility of these systems, the on-site environment for restoration measures, and the necessary gear/systems, the authors were able to secure means of long-term cooling of the PCV, and further enhance PCV reliability.

Function of Isolation Condenser of Fukushima Unit-1 Nuclear Power Plant

2012 ◽  
Author(s):  
Masanori Naitoh ◽  
Hiroaki Suzuki ◽  
Hidetoshi Okada
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Failure Time ◽  
Sea Water ◽  
Water Injection ◽  
Heat Removal ◽  
Severe Accident ◽  
Power Station ◽  
Fukushima Daiichi ◽  
Fire Engine

The Tohoku Region Pacific Coast Earthquake with magnitude 9.0 occurred at 2:46 PM of March 11th, 2011, followed by a huge Tsunami. The Fukushima Daiichi nuclear power station suffered serious damages from the Tsunami, involving core melt and release of large amount of fission products to an environment. The station blackout (SBO) occurred due to submergence of emergency equipment by the sea water. The isolation condenser (IC) was the only device for decay heat removal at the unit-1 of the Fukushima Daiichi nuclear power station after the reactor scram. The IC function was analyzed with a severe accident analysis code SAMPSON. The analysis results showed that (1) core melt resulting in RPV failure occurred since the IC operation was limited because it was not designed as a countermeasure to mitigate severe accident progression in Japan and (2) even assuming the continuous IC operation after the SBO to mitigate severe accident progression, the RPV failure occurred at 18:52, March 12th. However, since the alternate water injection by a fire engine was actually ready to start at 5:46, March 12th, which was earlier than calculated RPV failure time, the RPV failure could be prevented by continuous IC operation.

scholarly journals Important Severe Accident Research Issues After Accident at Fukushima Daiichi Nuclear Power Station

2013 ◽  
Author(s):  
Jun Sugimoto
Keyword(s):  
Nuclear Power Station ◽  
Working Group ◽  
Nuclear Power ◽  
Severe Accident ◽  
Power Station ◽  
Fukushima Accident ◽  
Research Issues ◽  
Containment Vessel ◽  
Accident Research ◽  
Fukushima Daiichi

After the accident at Fukushima Daiichi Nuclear Power Station several investigation committees issued reports with lessons learned from the accident in Japan. Among those lessons, some recommendations have been made on severe accident research. Similar to the EURSAFE efforts under EU Program, review of specific severe accident research items was started before Fukushima accident in working group of Atomic Energy Society of Japan (AESJ) in terms of significance of consequences, uncertainties of phenomena and maturity of assessment methodology. Re-investigation has been started after the Fukushima accident in this working group. Additional effects of Fukushima accident, such as core degradation behaviors, sea water injection, containment failure/leakage and re-criticality have been covered. The review results are categorized in ten major fields; core degradation behavior, core melt coolability/retention in containment vessel, function of containment vessel, source term, hydrogen behavior, fuel-coolant interaction, molten core concrete interaction, direct containment heating, recriticality and instrumentation in severe accident conditions. In January 2012, Research Expert Committee on Evaluation of Severe Accident was established in AESJ in order to investigate severe accident related issues for future LWR development and to propose action plans for future severe accident research, in collaboration with this working group. Based on these activities and also author’s personal view, the present paper describes the perspective of important severe accident research issues after Fukushima accident. Specifically those are investigation of damaged core and components, advanced severe accident analysis capabilities and associated experimental investigations, development of reliable passive cooling system for core/containment, analysis of hydrogen behavior and investigation of hydrogen measures, enhancement of removal function of radioactive materials of containment venting, advanced instrumentation for the diagnosis of severe accident and assessment of advanced containment design which excludes long-term evacuation in any severe accident situations.

scholarly journals Contamination of Fukushima Daiichi Nuclear Power Station with actinide elements

2019 ◽  
Vol 107 (9-11) ◽  
pp. 965-977
Author(s):  
Yoshikazu Koma ◽  
Erina Murakami
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Analytical Data ◽  
Fission Products ◽  
Great Earthquake ◽  
Contaminated Water ◽  
Power Station ◽  
Containment Vessel ◽  
Fukushima Daiichi ◽  
Actinide Elements

Abstract The Fukushima Daiichi Nuclear Power Station, which is owned by the Tokyo Electric Power Company, was damaged by the great earthquake and tsunami on March 11, 2011, and serious contamination due to radioactive nuclides occurred. To investigate the waste management methodologies, contaminated materials were radiochemically analyzed. This paper reviews the analytical data concerning actinide elements. Contaminated water has accumulated in the basement of the reactor and other buildings, and actinide nuclides have been detected in this water. Actinides first get dissolved into the water inside the primary containment vessel, and then their concentration in the water decreases to a certain level with further flow. The contaminated water is chemically decontaminated; however, the actinide concentration does not decrease with time. This suggests that the actinides are continuously being supplied by the damaged fuel via slow dissolution. The dissolved transuranic (TRU) nuclides are recovered in the precipitate via a chemical treatment and are mostly removed from the water. Pu, Am, and Cm were detected in the topsoil at the site and appear to originate from the damaged fuel, whereas the detected U originates from natural sources. TRU nuclides slowly move in soil to deeper layers. The contamination of the rubble is nonuniform, and actinides are detected as well as fission products. Inside the reactor building of unit #2, the TRU nuclide concentration is comparatively higher near the boundary of the primary containment vessel, which experienced a fault during the accident. As for the vegetation, TRU nuclides were only found in fallen leaves near the reactor buildings.

Research about the Hydrogen Removal Verification Method through Porous Medium of Silver Zeolite in Nuclear Power Station

2020 ◽  
Vol 999 ◽  
pp. 31-38
Author(s):  
Qing Bo Bao ◽  
Jian Hu ◽  
Shao Fei Zhou
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Evaluation Method ◽  
Natural Circulation ◽  
Catalyst Layer ◽  
Severe Accident ◽  
Test Device ◽  
Power Station ◽  
Verification Method ◽  
Silver Zeolite

After severe accident in the nuclear power station, it is necessary to remove the hydrogen timely for the purpose of preventing the containment integrity from breach. This report has investigated and studied the role of silver zeolite in the reaction of hydrogen and oxygen. According to the catalyst role, the principle test device for hydrogen removal with silver zeolite is provided. The force of natural circulation for principle test device is created by the Chimney Effect, which is the result of different density between the internal and external of the device. Also, this report suggests the flowing capability calculation method of up-thrust about the mixture gas passing through the catalyst layer of silver zeolite. The evaluation method of hydrogen removal efficiency with silver zeolite is described. Finally, this report gives the method of CFX numeric analog and the specific simulating steps for the layer of silver zeolite using for catalytic role.

UK support for Hinkley Point is likely to continue

2016 ◽  
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Investment Decision ◽  
Electricity Sector ◽  
Electricity Supply ◽  
Power Station ◽  
Content Type ◽  
The United Kingdom ◽  
The Uk

Subject The project to build a new nuclear power station at Hinkley Point. Significance Reports that construction of the planned nuclear power station at Hinkley Point may be postponed will raise further concerns about the project's prospects as well as the long-term direction of the UK electricity sector. The reports follow weeks of debate in the United Kingdom and France over whether construction should go ahead and over further delays in the final investment decision on the project (now scheduled for May). Impacts Depending on how the French government decides to support EDF, approval by the European Commission may be needed. The Austrian government has legally challenged the Commission's approval of UK plans to support the project. The UK government's existing plans for maintaining electricity supply -- the so-called 'capacity auctions' -- may need to be revisited.

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