December 15th, 2011 – BWR Industry Perspective on Reliable Hardened Vents

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BWR Industry Perspective on Reliable Hardened Vents

Greg Krueger (Exelon)

Nuclear Regulatory Commission
December 15, 2011
Rockville, MD


NRC has identified installation of Reliable Hardened Vents in Mark I’s and II’s as a significant issue
BWROG has taken and is taking actions to address the issue
BWROG proposes to provide near-term preliminary recommendations to facilitate issue resolution
Significant issues remain to be addressed


Tier 1 NRC recommendations
Recommendation sequencing and execution
(Industry Flex approach)
BWR Hardened Wetwell Vent (HWWV) actions
Issues to be addressed

Understand current NRC views on resolution of Reliable Hardened Vent issues as stated in recent SECYs and SRMs
Provide current BWROG actions to address Reliable Hardened Vent issues
Discuss potential near term BWROG actions and interactions with NRC on Reliable Hardened Vent issue
Apply the lessons-learned from the Fukushima accident to further enhance the safety margins of the U.S. reactor fleet

NRC Tier 1 Recommendations

2.1 Seismic and flood hazard re-evaluations
2.3 Seismic and flood walkdowns
4.1 SBO regulatory actions
4.2 10CFR50.54(hh)(2) recommendations
5.1 Reliable Hardened Vents – Mk I’s and II’s
7.1 SFP instrumentation
8 EOP, SAMG, EDMG integration
9.3 EP regulatory actions

Industry Flex Approach

Presented to NRC on 12/1/2011
BWROG will evaluate Reliable Hardened Vent issues in the context of this Flex approach
• Holistic approach needed for responding to Tier 1 recommendations

Flex Functions

Water and electric power generating source
Capability to inject cooling water into core and spent fuel pool
Power for instrumentation and control Heat removal
• Core, fuel pool and containment
Could include other functions or equipment to protect/mitigate beyond DB external events


Mark I containments
• 1990: Design criteria for HWWV accepted by NRC
– Path from wetwell vapor space to suitable release point
– Loss of decay heat removal sequences
– Sized for 1% of rated thermal power at Primary Containment Pressure Limit (PCPL)
– Operate up to PCPL
– No inadvertent actuation
– Vent path to 2nd containment isolation valve consistent with design basis
– Radiation monitoring available in Control Room
– No ignition sources in the pipeway
• 50.59 implementation

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