3-1-2013 Letter from VY to NRC Plan for Reliable ... - State of Vermont

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AREVA NP Inc.ANP-3203Revision 0Vermont Yankee Nuclear Power Station’s Overall Integrated PlaninResponse to MarchCommission Order Modifying Licenses with Regard to Requirements for Reliable HardenedContainment Vents (Order Number LA-I 2-050)12,2012Page11Section 3: Operational characteristicsRequirement 121- Capacityto Vent Equivalent ofThe HCVS shall have the capacity to vent the steam/energy equivalent of 1 percent of licensed/ratedthermal power (unless a lower value is justified by anatyses),below the pnmaiy containment design pressure.ISG 1,2.1 Criteria:1%and be able to maintain containment pressureBeyond design basis external events such a prolonged SBO could result in the loss of active containmentheat removal capability. The primary design objective of the HCVS is to provide sufficient venting capacity toprevent a longterm overpressure failure of the containment by keeping the containment pressure below theprimary containment designthe PCPL. The PCPL may be dictated by other factors, suchthe maximum containment pressure at which the safety relief valves (SRV5) and the HCVS valves can beopened and closed.pressure andasThe NRC staff has determined that, for a vent sized under conditions of constant heat input at a rate equalto 1 percent of rated thermal power and containment pressure equal to the lower of the primary containmentdesign pressure the PCPL, the exhaust-flow through the vent would be sufficient to prevent thecontainment pressure from increasing. This determination istorus suppression capacity is typically sufficient to absorb the decay heat generated during the firstthree hours following the shutdown of the reactor with suppression pool the source of injection, thatdecay heat is typically than 1reactor and that decay heat continues to to well under 1 percent, thereafter. Licensees shall havean auditable engineering basis for the decay heat absorbing capacity of their suppression pools, selection ofventing pressure such that the HCVS will have sufficient venting capacity under such conditions to maintaincontainment pressure at or below the primary containment designthe PCPL. If required,venting capacity shall be to an appropriate level commensurate with the licensee’s ventingstrategy. Licensees may also a venting capacity sized under conditions of constant heat input at a ratelower than 1 percent of thermal power if it can be justified by analysis that primary containment designand the PCPL would not be exceeded. In where plants were granted, have applied, or planto apply for power uprates, the licensees shall 1 thermal power corresponding to the upratedthermal power. The basis for the venting capacity shall give appropriate consideration of where venting isbeing performed from (i.e.. wetwell or drywell) and the difference in between the d,ywell and thesuppression chamber. Vent sizing for multi-unit sites must take into consideration simultaneous venting fromall the units, and ensure that venting on one unit does not negatively impact the ability to vent on the otherunits.pressureendlessResponse (ref. ISG Item 1.2.1):The HCVS wetwell pathwillincreasedusebased on studies that have shown that theasat leastpercent of rated thermal power three hours following shutdown of thedecreaseusecasespercentpressure andpressurebe designed for venting steam/energy at a nominal capacity ofthe lower of thecontainment design pressure and the PCPL value.of 1912The1 %MWtthermal power at pressure of 56 psig. This pressurevalue assumes that the suppression pool pressure suppression capacity is sufficient toabsorb the decay heat generated during the first 3 hours. The vent would then be able toprevent containment pressure from increasing above the containment design pressure. As partbe confirmed.of the detailed design, the duration of suppression pool decay heat absorptionThe HCVSisstrategy as describedfollows:During theinitialintended for use as one element of a comprehensive core damage preventioninthe response to NRC Order EA-12-049, which is summarized ascoping period (Phase1>,iswillinstalled plant equipment is used to maintain theessential function of core cooling by taking suction from the condensate storage tank via theRCIC and HPCI systems.as1 %
AREVA NP Inc. ANP-3203Revision 0Vermont Yankee Nuclear Power Station’s Overall Integrated Plan in Response to March 12, 2012Commission Order Modifying Licenses with Regard to Requirements for Reliable HardenedContainment Vents (Order Number EA-12-050)P2Qe 12During Phase 2, the primary strategy is to transfer water from the west basin to the condensatestorage tank to supplement the water available for RCIC suction and injection to cool the core.For Phase 3 the reactor core cooling strategy is to place one loop of RHR into service. This willbe accomplished by powering up a 4160V Class 1E Switchgear Bus for RHR and RHR ServiceWater pumps by utilizing a 4160V RRC FLEX portable diesel generator and supplying the RHRHeat Exchanger with water from the cooling tower deep basin using the RHR Service Waterpumps and existing Alternate Cooling System piping.
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3-1-2013 Letter from VY to NRC Plan for Reliable ... - State of Vermont

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