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

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AREVA NP Inc.ANP-3203Revision0Vermont Yankee Nuclear Power Station’s Overall Integrated PlaninResponse to MarchCommission Order Modifying Licenses with Regard to Requirements for Reliable HardenedContainment Vents (Order Number EA-12-050)Response(ref.l$G Item 1.2.3):The HCVS containment isolation valves are normally closed AOVs that are air-to-open andspring-to-shut. TheDCMCR switch for each of the two in-series valvessame DC and motive air source12,2012PageSOV must be energized to allow the motive air to open the valve. Thewillwillhave a key-locked switch. Although thebe used, separate control circuits including switchesused for the two redundant valves to address single point vulnerabilities that may cause thepath to inadvertently open.The features that prevent inadvertent actuation are administrative controls and key lockswitchesstationinisthe MCR for the two ClVsinseries. Inadvertent action from the remote controlprevented by administrative controls and several manual steps to open the CIVs.Emergency operating procedures and Severe Accident Guidelines (SAG) provide clearguidance that the HCVS is not to be used to defeat containment integrity during any designbe designed to provide features toprevent inadvertent actuation due to a design error, equipment malfunction, or operator error,basis transients and accidents.Inaddition, the HCVSthat would provide net positivesuction head to the emergency core cooling system (ECCS) pumpssuch that any credited containment accident pressurewill(CAP>willbe15willflowbe available (inclusiveof a design basis loss-of-coolant accident (DBLOCA)). For the long term DBLOCA, credit forsuppression pool accident pressureiscredited to ensure adequate available NPSH for RHRand CS pumps. For Appendix R and SBO, credit for containment pressure is not required toensure adequate RHR and CS pump NPSH.Requirement 1.2.4- Monitorthe Status of the Vent SystemThe HCVS shall include a means to monitor the status of the vent system (e.g., valve position indication)from the control room or other location(s). The monitoring system shall be designed fordunng a prolonged SBO.ISG 1.2.4 Criteria:sustained operationPlant operators must be able to readily monitor the of the HCVS at all times, including being able tounderstand whether or not containment pressure/energy is being vented through the HCVS,not containment integrity been restored following venting operations, Licensees shall provide a meansto allow plant operators to readily determine, or have knowledge the foliowing system parameters:has(1) HCVS vent valves’ position (open or closed),(2) system pressure,and(3) effluent temperature.statusoland whether orOther important information includes the status of supporting systems, such availability of electrical powerand pneumatic supply pressure. Monitoring by means of pennanently installed gauges that aL or nearby,the HCVS control panel is acceptable. The staff will consider alternative approaches for system statusinstrumentation; howevei licensees must provide sufficient information justification for alternativeapproaches.The means to monitor system status shall support sustained operations during a prolonged SBO, and bedesigned to operate under potentially harsh environmental conditions that woiJd be expected following aloss of containment heat removal capability and SL3O. Power supplies to all instruments, controls,indications shall be from the same power sources supporting the HGVS operation. “Sustained operations”may include the ofportable equipment to provide alternate source ofpower to components tomonitor HCVS status. Licensees shall demonstrate instrument reliability via an appropriate combination ofuseanandasareandused
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)Page 16design. analyses. operating experience, and/or testing of channel components foi the following sets ofparametersaradiological conditions that the instruments may encounter under normal plant conditions, and duringand after a prolonged SBO event.• temperatures and pressure conditions as doscnbed under requirementloading from system operation.128.including dynamic• humidity based on instrument location and effluent conditionsResponse (ref. ISG Item 1.2.4):inthe HCVS.The design of the HCVS will have temperature and pressure monitoring downstream of the lastcontainment isolation valve. All flow path valves will have open and closed position indication.These HCVS indications will be at or near the same location as the valve control switches,which is the MCR and remote control station. Motive air/gas pressure and power sourcevoltage will be monitored (voltage for the 125 VOC station batteries can be monitored from theDC panels located in the cable spreading room).Power for the instrumentation for the remote control station will be from the safety related B-AS2 battery, its chargers and switchgear are located in the adjacent Diesel Generator room.Power from essential DC batteries will be used to supply the SOVs used to position the AOVs.Refer to the response to 1.2.2 for discussion on the power.The approximate range for the temperature indication will be 50°F to 600°F. The approximaterange for the pressure indication will be 0 psig to 120 psig. The upper limits are approximatelytwice the required design containment temperature and pressure. The ranges will be finalizedwhen the detailed design and equipment specifications are prepared.The detailed design will address the radiological, temperature, pressure, flow induced vibration(if applicable) and internal piping dynamic forces, humidity/condensation and seismicqualification requirements. Assumed radiological conditions are those expected after aprolonged SBO (without fuel failure), which will bound normal plant conditions.Requirement 1.2.5- Monitorthe Effluent Discharge for RadioactivityThe HCVS shall include a meansfrom operation of the HCVS The monitoring system shall provide indicationto monitor the effluent discharge for radioactiwty that may be releasedinlocation(s), and shall be designed for sustained operation during a prolonged SBO.ISG 12.5 Criteria:the control room or otherLicensees shall provide an independent means to monitor overall radioactivity that may be released from theHCVS discharge The radiation monitor does not need to meet the requirements of NUREG 0737 formonitored releases, nor does it need to be able monitor releases quantitatively to ensure compliance withTitle10 of the Code of Federal Regulations (10 CFR) Pa#1(A) or 10 CFR Section. 67A wide-rangemonitoring system to monitor the overall activity in the release providing indication that effluent from thecontainment environment that is passing by the monitor is acceptable The use of other existing radiationmonitoring capabilityinlieu of an independent HCVS radiation monitor is not acceptable because plantoperators need accurate information about releases coming from the containment via the HCVS in order tomake informed decisions on operation of the reliable hardened venting system
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3-1-2013 Letter from VY to NRC Plan for Reliable ... - State of Vermont

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