Session: 06-02 Nuclear Codes, Standards, Licensing, & Regulatory Issues Session 2

Paper Number: 135279

135279 - Containment Depressurization Rate Requirements for Design Basis Loss-of-Coolant Accidents 

Abstract: 

Currently passive containment cooling system (PCCS) of HPR1000 is used in design extension conditions. PCCS uses loop heat pipes with evaporators inside the containment and condensers and a large pool outside the containment. PCCS has 6 trains, and each train can transfer 20% of design thermal load. PCCS has finished demonstration tests and is used in the first HPR1000 nuclear power plant - Fangchenggang nuclear power plant Units 3&4. One of HPR1000 potential modifications is using PCCS to mitigate design basis accidents, but there is an issue of containment depressurization rate. Section 6.2.1.1.A of Standard Review Plan (SRP) requires “To satisfy the requirements of GDC 38 to rapidly reduce the containment pressure, the containment pressure should be reduced to less than 50% of the peak calculated pressure for the design basis loss-of-coolant accident within 24 hours after the postulated accident. If analysis shows that the calculated containment pressure may not be reduced to 50% of the peak calculated pressure within 24 hours, the organization responsible for SRP Section 15.0.3 should be notified.” Due to the working principles of PCCS and layout space in the containment, it’s difficult for PCCS to reduce the containment pressure to less than 50% of the peak calculated pressure for the design basis loss-of-coolant accident within 24 hours after the postulated accident. Safety requirements of nuclear safety regulations, guides, standards and utility requirements documents in China and United States of America are analyzed, including 10 CFR Part 50, Section 6.2.1.1A of SRP, Section 15.0.3 of SRP, Regulatory Guide (RG) 1.183, RG 1.195, ANSI/ANS-56.4-1983(R1988), URD, HAF102, HAD-102/06-2020, NB/T 20404-2017, NB/T 20444-2017RK etc.. Design features for meeting containment depressurization rate requirements of typical light water cooled reactors (LWR) are analyzed, including LWRs with active safety systems, and passive safety systems. CPR1000 uses safety classified containment spray system supported by component cooling system and service water system. U.S EPR uses safety classified safety injection system supported by component cooling system and service water system and the safety injection system will switch to hot leg and cold leg simultaneous injection. AP1000 uses safety classified passive containment cooling system  and steel containment, but the water temperature sprayed to the outside surface of the steel containment is low. Solutions for HPR1000 are proposed. Loss of coolant accident is analyzed for HPR1000, which demonstrates that after increasing the heat transfer area and the design pressure of the containment, HPR1000 can meet the containment depressurization rate requirement.  

Presenting Author: Hua Zheng NA

Presenting Author Biography: ZHENG Hua graduated from Tsinghua University with a bachelor degree in 2002 and a master degree in 2005.
Since 2005, ZHENG Hua has worked in China Nuclear Power Engineering. Co. LTD. ZHENG Hua has participated in CPR1000, EPR, and HPR1000 nuclear power plant projects, including research and development, engineering design, design management.
Since 2010, ZHENG Hua has worked on HPR1000 R&D and continuous modification.
Since 2020, ZHENG Hua has worked on small modular reactors R&D, including NHR200-II design cooperation with Tsinghua University.

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