ML092790558

Response to Request for Additional Information Regarding NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems.

ML092790558
Person / Time
Site:	Nine Mile Point
Issue date:	09/29/2009
From:	Belcher S Constellation Energy Group, Nine Mile Point
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-08-001
Download: ML092790558 (10)

Text

Sam Belcher P.O. Box 63 Vice President-Nine Mile Point Lycoming, New York 13093 315.349.5200 315.349.1321 Fax 0 Constellation Ene ry-Nine Mile Point Nuclear Station September 29, 2009 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:

Document Control Desk

SUBJECT:

Nine Mile Point Nuclear Station, LLC Unit Nos. 1 & 2; Docket Nos. 50-220 & 50-410 Response to Request for Additional Information Regarding NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems"

REFERENCES:

(a) Letter from S. Belcher (NMPNS) to Document Control Desk (NRC) dated July 6, 2009, "Supplemental Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (b) Letter from K. J. Polson (NMPNS) to Document Control Desk (NRC) dated October 14, 2008, "Nine-Month Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (c) Letter from R. V. Guzman (NRC) to S. L. Belcher (NMPNS) dated August 17, 2009, "Request for Additional Information Regarding Nine Mile Point Nuclear Station, "Unit Nos. 1 and 2, Response to Generic Letter 2008-01, Managing Gas" Accumulation

'in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (TAC Nos. MD7848 and MD7849)By letters dated July 6, 2009 and October 14, 2008 (references a and b), Nine Mile Point Nuclear Station, LLC (NMPNS) submitted responses to Generic Letter (GL) 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," for Nine Mile Point Nuclear Station, Unit Nos. 1 and 2 (NMP1 and NMP2). The Nuclear Regulatory Commission (NRC)staff reviewed those responses and determined that additional information was needed to support its review. Attachment 1 to this letter provides responses to the Request for Additional Information (RAI)documented in the NRC's letter dated August 17, 2009 (reference c).Attachment 2 lists the regulatory commitment identified in this submittal.

Document Control Desk September 29, 2009 Page 2 Should you have any questions regarding this submittal, please contact T. F. Syrell, Licensing Director, at (315) 349-5219.Very truly yours, STATE OF NEW YORK TO WIT: COUNTY OF OSWEGO I, Sam Belcher, being duly sworn, state that I am Vice President-Nine Mile Point, and that I am duly authorized to execute and file this response on behalf of Nine Mile Point Nuclear Station, LLC. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other Nine Mile Point employees and/or consultants.

Such information has been reviewed in accordance with company practice and I believe it to be reliable.Subscribed and sworn before me, a Notary Public in and for the State of New York D 9this Gk day of e~ e¢qi ,2009.and County of WITNESS my Hand and Notarial Seal: Notary Public My Commission Expires: Date SB/RJC p raftblwftSam*

d Nw York 0106292203 Attachments:

1. Response to Request for Additional Information Regarding NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" 2. List of Regulatory Commitments cc: R. V. Guzman, NRC Project Manager S. J. Collins, NRC Regional Administrator, Region I NRC Resident Inspector ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS" Nine Mile Point Nuclear Station, LLC September 29, 2009 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS" By letters dated July 6, 2009 and October 14, 2008 (references a and b), Nine Mile Point Nuclear Station, LLC (NMPNS) submitted responses to Generic Letter (GL) 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," for Nine Mile Point Nuclear Station, Unit Nos. I and 2 (NMP1 and NMP2). The Nuclear Regulatory Commission (NRC)staff reviewed those responses and determined that additional information was needed to support its review. Responses to the Request for Additional Information (RAI) documented in the NRC's letter dated August 17, 2009 (reference c) are shown below. Each individual NRC request is repeated (in italics), followed by the NMPNS response.RAI-1 It is not clear what "Upon NRC approval of the TSTF Traveler" means. Clarify the schedule for review of the generic Technical Specifications and the possible submission of a License Amendment Request.Response NMPNS will monitor the industry resolution of the gas accumulation Technical Specification (TS) issues and, within no greater than 6 months following NRC approval of the Technical Specification Task Force Traveler (TSTF) or Consolidated Line Item Improvement Process (CLIIP) Notice of Availability, will submit a license amendment request that reflects the approved generic change, as appropriate.

RAI-2 In Reference 4, it is stated that the "abnormal venting results or pipe void identification would be reported and evaluated in accordance with the Corrective Action Program (CAP)which ensures those conditions are evaluated for potential impact on the station ..." Clarify the meaning of "potential impact" and how it is determined' Describe the actions to be taken if the evaluation determines that there will be an impact on the station.Response Any time voiding is suspected to exist, a Condition Report (CR) is written. The most likely places for voiding to occur are in the NMP2 High Pressure Core Spray (HPCS), Low Pressure Core Spray (LPCS) and Residual Heat Removal (RHR) systems. These systems are vented monthly from their high points through hard pipe with view glasses installed, through tygon tubing or through a hard pipe tail piece. If any air is vented from these high points, procedures require a CR to be generated and the information to be sent to the system engineer for trending.

If air is vented, it is noted in the procedure (e.g., vented air for 15 seconds or bubbly flow for 5 seconds).

An assessment on the potential impact on system operability is performed as part of the evaluation.

When evaluating for "potential impact," consideration would be given to: a. Evaluating any potential degradation of pump performance, or gas binding of the pump (if the gas accumulation is on suction piping), any potential for a gas void in discharge piping resulting in a pressure pulsation and a short delay in injection flow or the potential for a pressure increase that could challenge a safety relief valve.b. The need for increased Ultrasonic Test (UT) inspections for gas accumulation.

c. The potential for gas migration to other high points (if the pump run was performed to flush voids) and the need for additional confirmatory UTs required to ensure piping is maintained full of water.I of 5 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS" d. Industry guidance such as NEI APC 09-20 (reference d) for suction side voiding, Fauske report FAI/08-70, Rev. I (reference e), for discharge side voiding, and other BWROG guidance documents are used for assessment of the impact of voiding.RAI-3 Clarify whether the fill and vent procedures are able to ensure that gas was successfully vented and gas was not transported to a previously inspected high point.Response The venting and filling procedures are able to ensure that gas is successfully vented and not transported to a previously inspected high point by venting the lowest point first and then proceeding upwards to the highest points. When system filling and venting is completed, the system is run in the test mode to sweep any minor voids to the suppression pool.RAI-4 In Reference 4, it is stated that "it is concluded that the voided section of piping is not adverse to the operation of the RHR [residual heat removal] system in the shutdown cooling mode. " Clarify what is intended by "adverse to the operation" and describe the criteria used to determine what is "adverse to the operation." Discuss how the stated conclusions apply to other operational modes including expected accident conditions.

Response "Adverse to the operation" of RHR is intended to mean that any voiding would not impact any safety function of RHR or its shutdown cooling function.

The voiding in the RHR system was found in the Shutdown Cooling System piping downstream from its discharge isolation valve. In this case, the criteria used to determine that voiding is not "adverse to the operation" of RHIR is that the portion of RHR where voiding was found is isolated by the Shutdown Cooling discharge isolation valve. The Shutdown Cooling System piping is only placed in operation when the reactor is in a low energy state (reactor pressure less than 130 psig), and under those conditions the Shutdown Cooling discharge isolation valve is slowly throttled open. When this is done, any voiding is swept into the reactor as part of shutdown cooling. In all other modes of RHR, the voiding is isolated from the rest of RHR with the Shutdown Cooling discharge isolation valve shut.RAI-5 The licensee does not discuss the methods used to determine the volume of voids; nor are procedures concerning void volume determination mentioned as needed to be developed or revised Clarify whether procedures to measure the volume of voids and to measure the amount of gas that is actually vented will be developed, or describe existing measurement procedures.

Response When the HPCS, LPCS or RHR systems are vented, if air is vented, it is required to be noted (e.g., vented air for 15 seconds or bubbly flow for 5 seconds) in the procedure and the procedure directs a CR to be initiated.

A qualitative assessment of the void volume and its impact would be determined as part of the CR evaluation.

2 of 5 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS" RAI-6 The licensee states that if a void is detected during surveillance testing or other activities, then it will be evaluated in accordance with the CAP. Clarify what is involved in evaluating a void in accordance with the CAP.Response When evaluating a CR for potential impact, consideration would be given to: a. Potential degradation of pump performance.

b. The need for increased Ultrasonic Test (UT) inspections.

c. The potential for gas migration to other high points.d. Industry guidance.Refer to the RAI-2 Response for a detailed description of the above four considerations.

RAI-7 Training was not identified in GL 2008-01, but is considered to be a necessary part of applying procedures and other activities when addressing the issues identified in the GL.Briefly discuss training.Response In January 2008, following the Generic Letter 2008-01 publication, the original letter with its industry experience was presented for discussion to NMP2 Licensed Operators while they were in their training cycle. This included the industry Operating Experience associated with the Generic Letter 2008-01 and the process the site would go through to determine voiding at Nine Mile Point. Subsequently, GL 2008-01 was presented to licensed operators for both NMPI and NMP2 during their next continued training.

The generic letter has been added to the initial training programs in the Industry Experience and Human performance objectives of the Emergency Core Cooling Systems (ECCS) lesson plans and, as such, will be included in future NMP2 RHR System training to Licensed Operators.

Elements of the voiding in the RHR system and Low Pressure Core Spray (LPCS) were included in the LPCS system refresher for NMP2 Licensed Operators.

RAI-8 Justify the conclusion that a Froude number of less than 0.8 will ensure that air will not be ingested into the core spray and containment spray strainers with respect to the criteria of Reference 6.Response The criteria of Reference 6 in the Request for Additional Information letter (reference c) is related to gas movement in suction lines and pump response to gas, whereas the evaluation that was performed determined whether air will be entrained into the core spray or containment spray strainers from the suppression pool surface as a result of vortex formation.

The testing performed per NUREG/CR-2772 (reference f) observed there were no or nearly no air-withdrawal or vortices formed when the Froude Number was less than or equal to 0.8 for any of the tested configurations.

For Core Spray, the calculated Froude Number is 0.44 for 1 pump operation and 0.60 for 2 pump operation.

For Containment Spray, the calculated Froude Number is 0.31 for 1 pump operation and 0.62 for 2 pump operation.

Given that the calculated Froude Numbers for the containment spray and core spray strainers are well within 0.8, air will not be ingested into the containment spray strainers from the suppression pool surface.3 of 5 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS" RAI-9 Discuss the conclusions that voids will not be ingested from the torus with respect to Generic Issue 193 where this conclusion has not been generally substantiated.

Response NMPNS is following the industry developments with respect to Generic Issue 193 (BWR ECCS Suction Concerns) and understands that it is an open item that needs resolution.

The GI-193 issue is related to possible failure of low pressure core cooling systems due to unanticipated, large quantities of entrained gas in the suction piping from the suppression pools in BWR Mark I containments.

Any follow-up required (design or procedure changes)will be addressed by NMPNS when further guidance is issued by the industry or NRC related to Generic Issue 193.RAI-10 Describe the procedures mentioned in Reference 4, section 3(b).Response The following procedures were modified as part of the Generic Letter 2008-01 evaluation:

NMPI: NI-OP-04, Shutdown Cooling System.The procedure was revised to add a second venting of Shutdown Cooling piping with a minimum of 5 minutes delay between venting.NMP2: N2-OSP-CSH-MOO 1, HPCS Discharge Piping Fill and Valve Line-Up Verification N2-OSP-CSL-M00 I, LPCS Discharge Piping Fill and Valve Line-Up Verification N2-OSP-RHS-M00 1, RHR Discharge Piping Fill (LPCI) & Valve Lineup Verification In each of these procedures, Generic Letter 2008-01 was added as a reference.

Steps in each of the procedures specify that "when performing venting, the amount of air vented needs to be quantified to the best of your ability (e.g. five 1 inch bubbles, vented air for 15 seconds)." The procedures also specify that if air is vented write a CR and send information to the System Engineer for trending.N2-SOP-03, Loss of AC Power The procedure was revised to direct that any pump that was running and is now off due to loss of power be placed in Pull to Lock until that system is verified to be filled.N2-OP-3 1, Residual Heat Removal System N2-OP-32, Low Pressure Core Spray N2-OP-33, High Pressure Core Spray System The procedures were revised to vent for 2 minutes after filling and then run pump to sweep any remaining voids.4 of 5 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING NRC GENERIC LETTER 2008-01, "MANAGING GAS ACCUMULATION IN EMERGENCY CORE COOLING, DECAY HEAT REMOVAL, AND CONTAINMENT SPRAY SYSTEMS"

REFERENCES:

(a) Letter from S. Belcher (NMPNS) to Document Control Desk (NRC) dated July 6, 2009, "Supplemental Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (b) Letter from K. J. Poison (NMPNS) to Document Control Desk (NRC) dated October 14, 2008, "Nine-Month Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (c) Letter from R. V. Guzman (NRC) to S. L. Belcher (NMPNS) dated August 17, 2009, "Request for Additional Information Regarding Nine Mile Point Nuclear Station, Unit Nos. I and 2, Response to Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" (TAC Nos. MD7848 and MD7849)(d) Letter (APC 09-20) from J H. Riley (NEI) to Administrative Points of Contact dated May 18, 2009, Generic Letter (GL) 2008-01,"Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," -Evaluation of Unexpected Voids or Gas Identified in Plant ECCS and Other Systems (e) Fauske Report FAI/08-70, Rev. 1, "Gas-Voids Pressure Pulsations Program," dated September 2008 (f) NUREG/CR-2772, "Hydraulic Performance of Pump Suction Inlets for Emergency Core Cooling Systems in Boiling Water Reactors," dated June 1982 5 of 5 ATTACHMENT 2 LIST OF REGULATORY COMMITMENTS Nine Mile Point Nuclear Station, LLC September 29, 2009 ATTACHMENT 2 LIST OF REGULATORY COMMITMENTS The following table identifies an action committed to in this document by Nine Mile Point Nuclear Station, LLC (NMPNS). Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.

Direct questions regarding this commitment to T. F. Syrell, Licensing Director, at (315) 349-5219.REGULATORY COMMITMENT DUE DATE NMPNS will monitor the industry resolution of the gas accumulation Technical Specification (TS) issues and, within no greater than 6 months following NRC approval of the Technical Specification Task Force fraveler (TSTF) or Consolidated Line Item Improvement Process (CLIIP) Notice of Availability, will submit a license amendment request that reflects the approved generic change, as appropriate.

6 months following NRC approval of the TSTF or CLIIP Notice of Availability 1 of 1