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Evaluation and integral analysis of ADS and CMT failures during AP1000 SBLOCA with ASYST VER 3 simulation code

Omer Elsiddig Osman ORCID logo , Alya A. Badawi EMAIL logo and Ayah Elshahat
From the journal Kerntechnik


This research focuses on verifying the importance of the ADS and the CMT, by using the ASYST code. We evaluated the role of these two components by postulating the failure of the ADS as a single failure approach and the failure of the CMT with ADS failure as multiple failures approach during hypothetical SBLOCA conditions. These accidents acted as confounding factors distorting the AP1000 PSS. We investigated the reactor and safety system behavior during the SBLOCA. We evaluated the importance and effectiveness of two components in reducing and mitigating the consequences of the accident. We checked the effectiveness of these components by comparing the importunity-related issues with and without these components during the accidents. We found that the ADS decreased the pressure, allowing natural circulation to quench the reactor core during the LOCA. During the failure of ADS, the vapor bubbles formed in the reactor vessel covering the fuel rods increased their temperature. The CMT borated water feeding quenched the actinides decay heat. The non-existence of the CMT resulted in decreasing the RCS. ASYST was compared to NOTRUMP to validate it capability to analyze thermal phenomena during accidents. It was found that in the AP1000, the ADS and CMT were considered as the overall importunity of the others PSS.

Corresponding author: Alya A. Badawi, Nuclear & Radiation Engineering Department, Faculty of Engineering, Alexandria University, Alexandria 21544, Egypt, E-mail:

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: The authors acknowledge the contributions of Dr. Allison and all member of Innovative Systems Software (ISS) for the permission to using the ASYST code and over all supports and assistance. This work was supported by National Council for Training in Sudan and Sudanese Nuclear and Radiological Regulatory Authority.

  3. Conflict of interest statement: The authors state that the publication of this paper does not include any conflicts of interest.


Allison, C.M., Hohorst, J.K., Pericas, R., Ezzidi, A., and Naitoh, M. (2021). Development and preliminary assessment of the new ASYST. In: Proceedings of The International Congress on Advances in Nuclear Power Plants (ICAPP). ANS, Abu Dhabi.Search in Google Scholar

Allison, C.M., Hohorst, J.K., and Ezzidi Nakata, A. (2022). RELAP/SCDAPSIM and ASYST VER 3 Fukushima related activities. In: International topical meeting on issue . Log nr: 19001 1, pp. 1–16.Search in Google Scholar

Ansaldo, D.L. (2013). Preoperational tests and design basis accidents simulations for a generation III + nuclear power plant. University of Pisa and Ansaldo Nucleare S.p.A.Search in Google Scholar

Banerjee, S., Ortiz, M.G., Larson, T.K., and Reeder, D.L. (1998). Scaling in the safety of next generation reactors. Nucl. Eng. Des. 186: 111–133, in Google Scholar

Burgazzi, L. (2012). Reliability of passive systems in nuclear power plants. In: Ahmed, W. (Ed.). Nuclear power – practical aspects. Intech, USA, pp. 22–58, in Google Scholar

Estévez-Albuja, S., Jiménez, G., and Vázquez-Rodríguez, C. (2021). AP1000 IRWST numerical analysis with GOTHIC. Nucl. Eng. Des. 372: 16, in Google Scholar

Hashim, M., Oshikawa, Y., and Yang, M. (2013). Addressing the fundamental issues in reliability evaluation of passive safety of AP1000 for a comparison with active safety of PWR. (Safety Simulat). Int. J. Nucl. 2: 147–159.Search in Google Scholar

Hashim, M., Hidekazu, Y., Takeshi, M., and Ming, Y. (2014). Application case study of AP1000 automatic depressurization system (ADS) for reliability evaluation by GO-FLOW methodology. Nucl. Eng. Des. 278: 209–221, in Google Scholar

Hashim, M., Yoshikawa, H., Matsuoka, T., and Yang, M. (2014). Quantitative dynamic reliability evaluation of AP1000 passive safety systems by using FMEA and GO-FLOW methodology. Nucl. Sci. Technol. 51: 526–542, in Google Scholar

Housiadas, C., Kissane, M., and Sehgal, R. (2012). Fission product release and transport. In: Nuclear Safety in light water reactors:severe accident phenomenology. Academic Press, UK, Chapter 5.Search in Google Scholar

IAE (2002). Natural circulation data and methods for advanced water cooled nuclear power plant designs. TECDOC-1281, pp. 18–21, Available at: in Google Scholar

IAEA (2001). Applications of probabilistic safety assessment (PSA) for nuclear power plants, IAEA-TECDOC-1200, Available at: in Google Scholar

IAEA (2002). Safety standards series, instrumentation and control system important to safety in nuclear power plants, NS-G-1.3, p. 99, Available at: in Google Scholar

IAEA (2009). Passive safety systems and natural circulation in water cooler nuclear power plants, IAEA-TECDOC-1624, p. 159, Available at: in Google Scholar

IAEA (2011). Status report 81 – advanced passive PWR (AP 1000). Vienna: IAEA.Search in Google Scholar

IAEA (2016). Considerations on the Application of the IAEA Safety Requirements for the Design of Nuclear Power Plants. Tecdoc Ser., no. 1791, p. 88, Available at: in Google Scholar

IRSN IAEA (2021). Anticipation and Resilience, considerations a decate after the Fukushima Daiichi accident. Paris: IRSN- Mission Report.Search in Google Scholar

Juhn, P.-E., Kupitz, J., and Cleveland, J. (1997). Advanced nuclear power plants: highlights of global development, 39/2 edn. Vienna: International Atomic Energy Agency Bulletin.Search in Google Scholar

Kodeli, I. (1995). Neutron and gamma field characteristics after shutdown and a possible application to determine the coolant inventory. Nucl. Energy Cent. Eur.: 115–122.Search in Google Scholar

Lo Nigro, A., Auria, F.D., and Saiu, G. (2001). MSLB coupled 3D neutronics-thermalhydraulic analysis of a large PWR using RELAP5-3D. In: International Conference Nuclear Energy in Central Europe 2001, Portoroz (Slovenia), Available at: in Google Scholar

Malloy, J.D. and Bingham, B.E. (2014). Control system and method for pressurized water reactor (PWR) and PWR system including SAME. United States, Patent No. US 8,781,057 B2.Search in Google Scholar

Queral, C., Montero-Mayorga, J., Gonzalez-Cadelo, J., and Jimenez, G. (2015). AP1000®Large-Break LOCA BEPU analysis with TRACE code. Ann. Nucl. Energy 85: 576–589, in Google Scholar

Tobias, A. (1979). DECAY HEAT. Berkeley (Gloucestershire GL13 9PB). Prog. Nucl. Energy. 5: 1–9.10.1016/0149-1970(80)90002-5Search in Google Scholar

U.S.NRC (2007). Common-cause failure database and analysis system: event data collection, classification, and coding. NUREG/CR-6268, Available at: http://www.nrc.ov/readincq-rm.html.Search in Google Scholar

USNRC (2021). Glosary/design basis-accident, Available at: in Google Scholar

Wang, W., Su, G., Tian, W., and Qiu, S. (2013). Research on thermal hydraulic behavior of small-break LOCAs in AP1000. Nucl. Eng. Des. 263: 380–394, in Google Scholar

Westinghouse Electric Company (2009). Accident analysis chapter 15. AP1000 design controls document. Tier 2 material, revision 19.Search in Google Scholar

Xie, H. (2017). Numerical simulation of AP1000 LBLOCA with SCDAP/RELAP 4.0 code. Nucl. Sci. Technol. 54: 969–976, in Google Scholar

Received: 2022-01-31
Published Online: 2022-08-12
Published in Print: 2022-10-26

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