ML082890161

Nine-Month Response to NRC Generic Letter 2008-01, Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems

ML082890161
Person / Time
Site:	Cooper
Issue date:	10/10/2008
From:	Minahan S Nebraska Public Power District (NPPD)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-08-001, NLS2008081
Download: ML082890161 (22)

Text

Nebraska Public Power District "Always there when you need us" NLS2008081 October 10, 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" Cooper Nuclear Station, Docket No. 50-298, DPR-46

References:

1.

NRC Generic Letter 2008-01, "Managing Gas Accumulation in /

Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" dated January 11, 2008

2.

Letter from Stewart B. Minahan (NPPD) to USNRC Document Control Desk, dated September 11, 2008, "Request for Extension to Generic Letter 2008-01"

3.

Letter from Carl F. Lyon (USNRC) to Stewart B. Minahan (NPPD),

dated October 3, 2008, "RE: Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal:, and Containment Spray Systems," Proposed Alternative Course of Action (TAC No. MD7815)"

Dear Sir or Madam:

The purpose of this letter is to provide the Nebraska Public Power District's (NPPD) response to Nuclear Regulatory Commission (NRC) Generic Letter (GL) 2008-01 (Reference

1) for Cooper Nuclear Station (CNS). GL 2008-01 request that each licensee evaluate the licensing basis, design, testing, and corrective actions for the emergency core cooling, decay heat removal, and containment spray systems to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

GL 2008-01 requested each licensee to submit a written response in accordance with 10 CFR 50.54(f) within nine months of the date of the GL to provide the information summarized below:

a) A description of the results of evaluations that were performed pursuant to the above requested actions. This description should provide sufficient information to demonstrate COOPER NUCLEAR STATION P0. Box 98 / Brownville, NE 68321-0098 4/34 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www nppdcom k.p'

NLS2008081 Page 2 of 3 that you are or will be in compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems; b) A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that you determined were necessary to assure compliance with these regulations; and, c) A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule.

In summary, NPPD has concluded that the subject systems at CNS are in compliance with the Technical Specification definition of Operability, i.e., capable of performing their intended safety function and that CNS is currently in compliance with 10 CFR 50, Appendix B, Criterion III, V, XI, XVI and XVII, with respect to the concerns outlined in GL 2008-01 regarding gas accumulation in the accessible portions of these systems. Appropriate controls are in place to maintain compliance.

With respect to the inaccessible portions of the CNS systems within the scope of NRC GL 2008-01, these systems have reasonable assurance of Operability based on the justifications provided in Reference 2. NPPD has not identified any new information which changes the discussion nor the conclusions provided in Reference 2.

As committed in Reference 2, NPPD will complete its assessments of those inaccessible portions of these systems during Refueling Outage 25 or an outage of sufficient duration, which ever comes first, and provide a supplement to this report with those results no later than 90 days from startup of that outage. Reference 3 allows NPPD to implement its proposed alternative course of action provided that implementation is consistent with associated requests discussed in Reference 3.

The attachment to this letter contains the NPPD nine-month response to NRC GL 2008-01.

A list of new NRC commitments related to the nine-month response is also provided with this letter.

I declare under penalty of perjury that the foregoing is true and correct.

Executed On 06q1210 d;1&

2 (Date)

Sincerely, Stewart B. Minahan Vice President - Nuclear and Chief Nuclear Officer

/dm

NLS2008081 Page 3 of 3 cc:

Regional Administrator w/ attachment USNRC - Region IV Cooper Project Manager w/ attachment USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/ attachment USNRC - CNS Nebraska Health and Human Services w/ attachment Department of Regulation and Licensure CNS Records w/ attachment NPG Distribution w/ attachment

NLS2008081 Attachment Page 1 of 17 Nine-Month Response to NRC Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" This attachment contains the Cooper Nuclear Station's (CNS) nine-month response to Nuclear Regulatory Commission (NRC) Generic Letter (GL) 2008-01 "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," dated January 11, 2008. In GL 2008-01, the NRC requested that each addressee evaluate its Emergency Core Cooling System (ECCS), Decay Heat Removal (DHR) system, and containment spray system licensing basis, design, testing, and corrective actions to ensure that gas accumulation is maintained less than the amount that challenges operability of these systems, and that appropriate action is taken when conditions adverse to quality are identified.

The following information is provided in this response:

a) A description of the results of evaluations that were performed pursuant to the above requested actions. This description should provide sufficient information to demonstrate that you are or will be in compliance with the quality assurance criteria in Sections III, V, XI, XVI, and XVII of Appendix B to 10 CFR Part 50 and the licensing basis and operating license as those requirements apply to the subject systems (see Section A of this attachment);

b) A description of all corrective actions, including plant, programmatic, procedure, and licensing basis modifications that you determined were necessary to assure compliance with these regulations (see Section B of this attachment); and, c) A statement regarding which corrective actions were completed, the schedule for completing the remaining corrective actions, and the basis for that schedule (see Section C of this attachment).

The following systems were determined to be in the scope of GL 2008-01 for CNS:

a) High Pressure Coolant Injection (HPCI) System b) Core Spray (CS) System c) Residual Heat Removal (RHR) System (Low Pressure Coolant Injection (LPCI),

Suppression Pool Cooling (SPC), and Containment Spray modes)

NLS2008081 Attachment Page 2 of 17 A. EVALUATION RESULTS Licensing Basis Evaluation The CNS licensing basis was reviewed with respect to gas accumulation in the HPCI System, CS System, RHR System (LPCI, DHR, SPC, and Containment Spray modes).

This review included the Technical Specifications (TS), TS Bases, Updated Safety Analysis Report (USAR), the Technical Requirements Manual (TRM) and TRM Bases, responses to NRC generic communications, regulatory commitments, and License Conditions.

1. Summarization of Licensing Basis Review Results:

The above documents and regulatory commitments were evaluated for compliance with applicable regulatory requirements. A summary of the specific licensing basis is provided below:

The CNS TS has two applicable sections based on plant mode for the surveillance requirements (SR):

a) TS 3.5.1 for Operating Mode includes SR 3.5.1.1 which states "Verify, for each ECCS injection/spray subsystem, the piping is filled with water from the pump discharge valve to the injection valve."

b) TS 3.5.2 for Shutdown Mode includes SR 3.5.2.2 which states "Verify, for each required ECCS injection/spray subsystem, the piping is filled with water from the pump discharge valve to the injection valve."

The surveillances are performed on a 31-day frequency. Nebraska Public Power District (NPPD) has a procedure for venting the ECCS injection and spray subsystem piping in order to meet the requirements of SR 3.5.1.1 and SR 3.5.2.2. The purpose of this procedure, in part, provides instructions for station personnel to ensure each ECCS Injection/Spray Subsystem meets TS requirements.

The CNS TS Bases states the following:

SR 3.5.1.1 "The flow path piping has the potential to develop voids and pockets of entrained air. Maintaining the pump discharge lines of the HPCI System, CS System, and LPCI subsystems full of water ensures that the ECCS will perform properly, injecting its full capacity into the RCS upon demand. This will also prevent a water hammer following an ECCS initiation signal. One acceptable method is to vent from the system high point until water flow is observed. The 31 day Frequency is based on the gradual nature of void buildup in the ECCS piping, the procedural controls governing system operation, and operating experience."

NLS2008081 Attachment Page 3 of 17 The TS Bases for SR 3.5.1.1 is applicable to SR 3.5.2.2.

A search of the CNS USAR identified the following statements concerning ECCS discharge piping:

USAR Chapter VI-3, states, in part that "Each ECCS pump's discharge line is maintained filled and pressurized, from the pump discharge to the injection valve.

This prevents water hammer and possible pipe damage on system initiation. The water supply is from Reactor Building Auxiliary Condensate Supply System.

This system is non-essential and is not required for ECCS operation. A low-pressure alarm will alert control room operators of a potential loss of fill." HPCI[

also includes piping from the suction supply check valves.

USAR Chapter VII-4, states, in part that "The HPCI discharge lines are maintained full of water. The design is similar to the fill systems for the RHR and Core Spray Systems (see USAR Section VII-4.5.4.4). An alarm annunciates in the Main Control Room indicating possible loss of water filling the lines."

CNS TRM Section 3.3.2, ECCS and RCIC Instrumentation, contains the following statements:

TLCO 3.3.2 "The ECCS and RCIC instrumentation for each Function in Table T3.3.2-1 shall be OPERABLE."

D.1 "Vent discharge line high point vent. Immediately and 7 days thereafter."

The TRM Bases states "For Condition D, the high point vent shall be vented weekly upon failure of PS-73A or B, PS-266, PS-268, PS-269, PS-270."

2. Summarization of Changes to Licensing Basis Documents:

NPPD is not proposing changes to the CNS Licensing Bases Documents at this time.

The level of detail in current CNS Licensing Bases as it relates to gas intrusion is consistent with the current industry level of detail. However, NPPD is monitoring industry activities for developing TS changes (refer to the response to Licensing Basis Question 3).

3. List of Items not Completed, Schedule for Completion, and Basis for Schedule:

TS improvements are being addressed by the Technical Specifications Task Force (TSTF) to provide an approved TSTF Traveler for making changes to individual licensee's TS related to the potential for unacceptable gas accumulation. The development of the TSTF Traveler relies on the results of the evaluations of a large

NLS2008081 Attachment Page 4 of 17 number of licensees to address the various plant designs. NPPD is continuing to support the industry and Nuclear Energy Institute Gas Accumulation Management Team activities regarding the resolution of generic TS changes via the TSTF Traveler process. After NRC approval of the Traveler, NPPD will evaluate its applicability to CNS, and evaluate adopting the Traveler within 90 days of NRC approval to either supplement or replace the current TS requirements.

Design Evaluation The CNS design basis was reviewed with respect to gas accumulation in the HPCI, CS, and RHR LPCI, SPC, and Containment Spray modes. This review included piping design specifications, calculations and engineering evaluations.

1. Discussion of Design Basis Documents Review:

The applicable system flow diagrams and associated piping isometric drawings provide sufficiently detailed information regarding placement of vent, drain or test connections to fill and vent systems during return to service and permit periodic venting of gas accumulation during normal operation.

Design features and water level set points are controlled by design and operating procedures to prevent vortex effects that can potentially ingest gas into the system during design basis events. Engineering evaluation and analysis has shown that air entrainment due to vortex effects is not likely to occur with the CNS configuration and system operating conditions.

CNS has not performed plant specific calculations or analyses to confirm the acceptability of gas accumulation in the piping of the affected systems specific to responding to this GL. The TS application of "filled" was used for identification of potential void locations. "Filled" was interpreted as meaning that systems were water solid. Walk downs and drawing reviews were done using this criterion as the basis for identification. On identification of potential void locations, the operability of the systems was assessed using CNS operating experience and engineering judgment.

INPO SER 02-05 Rev. 0 identified several fill and venting concerns which were addressed with procedure revisions.

NRC IN 87-10 identified potential concerns with the use of suppression pool cooling and resulted in procedures revision.

Potential Shutdown Cooling (SDC) Water Hammer was addressed by Nuclear Steam System Supplier recommendations which resulted in NPPD implementing procedure revisions.

NLS200808 1 Attachment Page 5 of 17

2. Discussion of Interim Allowable (new applicable) Gas Volume Acceptance Criteria, Corrective Action Summarization, Including Schedule:

NPPD will use the joint industry evaluations as acceptance criteria to support operability of the systems if voids are identified based on the Boiling Water Reactor Owners' Group (BWROG) and Pressurized Water Reactor Owners' Group activities to evaluate and quantify acceptable amounts of gas in these systems. The evaluations consider the following:

Pump Casing and Pump Suction Piping. Industry joint working groups evaluated existing documentation and operating experience and provided guidance on acceptable gas volume for the ECCS pump suctions. This was determnined to be a bounding 2% void fraction for continuous voiding and up to 10% void fraction for up to 5 seconds. The guidance is based on the pump casing being properly vented with no gas voids in the pump casing when the pump is started.

These criteria will be applied as a guideline to support system operability until further industry investigation and review provides a definitive criterion. These values when used in conjunction with other factors such as Net Positive Suction Head, flow rate, and system pressure for which the system is credited provide a basis for evaluating system operability.

CNS procedures fill and vent the respective HPCI, CS and RHR system pump suction piping and pump casing in order to remove gas voids. The fill and venting process minimizes the likelihood of gas voids in the ECCS pump casings and suction piping.

Pump discharge piping which is susceptible to pressure pulsation (water hammer) after a pump start. An industry Joint Owner's Group program performed a study to document a conservative methodology for evaluating pump discharge piping gas accumulation. Gas accumulation in the piping downstream of the pump to the first closed isolation valve can result in amplified pressure pulsations after a pump start.

Subsequent pressure pulsations can cause relief valves in the subject systems to lift, or result in unacceptable pipe loads, i.e., axial forces that are greater than the design rating of the axial restraints.

The method recommends a guideline for bounding piping restraint loads in the subject systems to determine the acceptable gas volume accumulation such that pipe loading is within acceptable limits, i.e., axial forces that are less than the design rating of the axial restraint(s). It also recommends how to add the estimated pressure pulse to the pre-existing pipe pressure to establish a total pressure to compare to the relief valve set point.

NPPD will use this methodology as an initial bounding analysis. When desired, more specific analysis will be conducted. This can be used to establish the applicable limits for gas accumulation in the discharge piping of the affected ECCS systems.

NLS2008081 Attachment Page 6 of 17 A qualitative evaluation was done for the BWROG regarding the ECCS piping downstream of the first normally closed motor operated injection valves. The evaluation determined the existence of gas voids will have no adverse impact on the system piping because the pressure transient would not be greater than already considered in the design of the piping for an accident.

A qualitative evaluation was done for the BWROG regarding the affect of gas accumulation on ECCS analysis which concluded the existence of gas voids causing less than 4 second delay will have no adverse impact. Other plant events, such as loss of feedwater and anticipated transient without scram are bounded by the four second delay.

As stated above, NPPD will use the industry positions on suction and discharge voiding as established in the discussion above as interim guidance.

3. Summarization of Design Basis Documents Changes, including Schedule for Changes:

CNS did not identify any Design Basis documents that required revision. New documentation will be developed to implement the interim guidance identified in Section 2 of the Design Evaluation segment of this attachment.

4. Discussion of System P&ID and Isometric Drawing Reviews Results:

The HPCI, CS, and RHR system flow diagrams and associated piping isometric drawings were reviewed to identify vents and high points. In addition, hydraulic profiles were prepared using flow diagrams and piping isometrics to show elevation relative to major component locations. Profiles were prepared for the HPCI and CS systems to assist in system review of piping segments for potential high points where gas could possibly accumulate. Specifically, the following flow paths were reviewed (the RHR hydraulic profile for sections outside of containment is not completed and was not available to aid in this review):

a) HPCI suction from Emergency Condensate Storage Tank (ECST) to HPCI common suction tee, HPCI suction from Suppression Pool to common suction tee, HPCI suction, and HPCI discharge.

b) CS suction and CS discharge (accident flow path).

c) RHR suction from Suppression Pool and Condensate Storage Tank, LPCI, Containment Spray to Drywell and Suppression Pool.

Flow paths were reviewed to identify system vents and high points. This review was conducted in preparation for system walk downs and was done to familiarize the team with the systems. It did not eliminate any piping system locations from the physical walk down.

NLS2008081 Attachment Page 7 of 17 For initial scoping purposes, each high point was reviewed to determine if it could be effectively vented with an existing system vent. Horizontal line slope, horizontal line local high point information, and vent orientation details were obtained from the piping isometric drawings. The results of the reviews were provided to System Engineering to assist them in scoping system piping walkdowns.

NPPD considered piping system components such as vertical stem valves, swing check valves, piping expansion/reducers, flow orifices, and relief valve standpipes, as potential high points with unventable accumulated gas pockets.

5. Identification of New Vent Valve Locations, Modifications to Existing Vent Valves, or Utilization of Existing Vent Valves Based on Drawing Review:

No new vent valve locations or modifications were identified. System walkdowns did not identify any physical plant to drawing discrepancies with respect to vent valve locations.

6. Discussion of System Confirmation Walkdown Results:

The HPCI, CS, and RHR system flow diagrams and associated piping isometric drawings were reviewed to identify vents and high points. In addition, hydraulic profiles were reviewed for the HPCI and CS systems to assist in system review of piping segments for potential high points where gas could possibly accumulate.

As part of the system walk downs, each flow path was reviewed line by line to identify system vents and high points. The reviewed lines were highlighted on isometric drawings. The system high points included system piping (which includes improperly sloped piping), valve bodies, pump casings, and heat exchangers. In addition, pipe diameter transitions in horizontal lines that could trap gas such as pipe reducers and orifices were identified.

Individual sections of piping were reviewed and the results documented for each applicable system. These sections were reviewed using a walk down checklist. This checklist aided with the identification of potential areas for gas accumulation within the piping.

The areas with potential gas accumulation were identified within the Corrective Action Program (CAP). Operability reviews were completed in accordance with Regulatory Issue Summary (RIS) 2005-20 and the CNS procedure for evaluating operability. No operability concerns were identified that prevent any of the applicable systems from performing their intended safety function.

As identified in Reference 2, the station will perform walk downs of inaccessible piping in containment during the next outage of sufficient duration not to exceed Refueling Outage (RE-25).

NLS2008081 Attachment Page 8 of 17 High Pressure Coolant Injection The scope of the HPCI system walkdown included the suction pipe from the ECST, the suction pipe from the Suppression Pool, the HPCI injection to the steam tunnel penetration, and the auxiliary cooling water pipe. The HPCI injection pipe connection to Feedwater piping located in the steam tunnel was not walked down due to installation of a high point vent immediately upstream of the injection motor operated valve during RE-23 in October 2006.

As part of the walkdown, a sample of horizontal lines (selected based on length, size, design function, and initial walk down results) were checked for slope, utilizing the Zip Level tool, to ensure that slopes in the pipe would not prevent proper venting. These sections included portions of the suction piping from the Suppression Pool, suction piping from the ECST and the pump discharge piping.

Core Spray The CS system was walked down from the suction line Suppression Pool penetration to the discharge line drywell penetration. The CS Test Return line beyond the test line recirculation valve was not included in the walkdown since it does not contribute to the essential safety function of the CS System. Lines smaller than one inch (i.e. instrument tubing) were not evaluated due to the negligible potential contribution to system gas accumulation.

As part of the walkdown, a sample of horizontal lines (selected based on length, size, design function, and initial walk down results) were checked for slope, utilizing the Zip Level tool, to ensure that slopes in the pipe would not prevent proper venting.

Residual Heat Removal The RHR system walkdown consisted of comparing the piping configuration of both loops to the isometric drawings. The scope included the flow paths of greater than one inch diameter piping used for LPCI, SPC, Suppression Pool Spray, Drywell spray and RHR cross-tie piping. This walk down included piping up to the Primary Containment penetrations.

As part of the walkdown, a sample of horizontal lines (selected based on length, size, design function, and initial walk down results) were checked for slope, utilizing the Zip Level tool, to ensure that slopes in the pipe would not prevent proper venting.

Condition Reports (CRs) were written to address potential concerns for the three systems. These CRs identified unvented high points that may accumulate gas in locations such as suction header pipe size transition, gland seal condenser piping and components, auxiliary cooling line, upstream to the flow element, under closed valves and relief valves in a vertical piping, and sloped and capped piping with no vent

NLS2008081 Attachment Page 9 of 17 point. The CRs also provide a vehicle for the performance of Ultrasonic Testing (UT) on the identified sections of piping.

The individual CRs for each system were combined into three CRs corresponding to each of the three systems. Cumulative operability was determined for the three systems. The systems were determined to be operable.

The CR evaluations include actions to determine the locations and schedule for installation of future vent valves for the subject systems. Vents will be installed, as necessary, in the appropriate locations to facilitate gas accumulation removal, no later than the conclusion of RE-25.

In the interim, NPPD will conduct UT of locations identified in the CRs by February 27, 2009. The UTs will provide additional confirmation that HPCI, CS, and RHR are operable and assist in determining future vent locations.

Should the UT identify air pockets or voided piping, a new CR is required, per the CAP process, and operability will be assessed based on what is discovered. The cumulative effect of any air or voided piping will be subsequently assessed for cumulative effect on the system.

7. Identification of New Vent Valve Locations, Modifications to Existing Vent Valves, or Utilization of Existing Vent Valves Based on Confirmatory Walkdowns. Identification of Remaining Walkdowns:

Based on initial reviews of the walkdowns, no immediate need for additional venting or vent valves were identified. Condition reports are being reviewed and evaluated in CAP. See Section 6 of the Design Evaluation segment of this attachment for additional detail.

Walk downs have been completed except for those portions identified in Reference 2.

Since the submittal of Reference 2, no new walkdowns have been identified. The scope of the remaining walkdowns described in Reference 2 remains unchanged.

8. Discussion of Fill and Vent Activities and Procedure Review Results:

A review was performed for procedures used to fill and vent the subject system piping susceptible to gas accumulation. Following outages and maintenance activities which drain the system, operating procedures are used to fill and vent the subject systems. These procedures, coupled with post-maintenance testing and surveillance test procedures, provide assurance that the subject systems are purged of air and other non condensable gases prior to restoration to operable status.

NLS2008081 Attachment Page 10 of 17

9. Identification of Procedure Revisions, or New Procedures Resulting from Fill and Vent Activities and Procedure Reviews. Summarization of Associated Corrective Actions and Associated Schedule:

No procedure revisions or new procedures are required to restore compliance with regulatory requirements.

The RHR fill and vent procedure is adequate for normal venting of the system. The procedure utilized for fill and vent of cross-tie piping will be updated by adding valve manipulations for flushing the piping to rad waste (RW) by March 3, 2009. This change will eliminate the potential for gas accumulation in this section of RHR piping.

NPPD will revise the fill and vent procedures to use UT to provide additional assurance the systems are filled by March 3, 2009.

NPPD will evaluate improvements to fill and vent procedures reviewing flow rates to determine impact on gas accumulation. If required, procedures will be changed to incorporate the review results. This action is being tracked in CAP.

NPPD will evaluate revising the engineering procedures to consider potential gas accumulation concerns and use of adequate high point vents. This action is being tracked in CAP.

10. Discussion of Potential Gas Intrusion Mechanisms:

Suction vortex gas entrainment has been evaluated previously to address industry concerns. HPCI suction transfer from ECST to Suppression Pool was evaluated based on hydraulic flow testing. It was concluded that gas entrainment by vortex formation is not likely to occur under the proposed worst case conditions. The above conclusions are supported by a CNS specific engineering evaluation document.

11. Ongoing Industry Programs:

As part of general industry participation initiatives and operating experience reviews, NPPD is monitoring ongoing industry programs regarding gas accumulation and its affects.

NLS2008081 Attachment Page 11 of 17

12. Detailed List of Items that have Not Been Completed, a Schedule for Their Completion, and the Basis for that Schedule:

Reference Items Not Schedule for Basis for Commitment Section Completed Completion Schedule (Yes or No)

Design, 2 NPPD will January 27, Acceptance Yes incorporate 2009 criteria to be industry guidance utilized to in regards to support allowable suction acceptability of void fraction.

UT results for open CRs.

Design, 2 NPPD will January 27, Same basis as Yes incorporate the 2009 above.

industry guidance on establishing gas accumulation limits in the discharge piping of the effected ECCS systems.

Design, 6 NPPD will During the Basis provided Yes complete the next outage of in Reference 2.

necessary sufficient walkdowns duration, no within CNS later than the Primary conclusion of Containment.

RE-25.

Design, 6 Vents will be No later than The systems are Yes installed, as the conclusion currently necessary, in the of RE-25.

determined to be appropriate operable. The locations to addition of vent facilitate gas valves improves accumulation the management

removal, of gas accumulation.

NLS2008081 Attachment Page 12 of 17 Reference Items Not Schedule for Basis for Commitment Section Completed Completion Schedule (Yes or No)

Design, 6 NPPD will February 27, The UTs will Yes conduct UT of 2009 provide locations additional identified in the confirmation that CRs to provide HPCI, CS, and additional RHR are confirmation that operable and HPCI, CS, and assist in RHR are operable determining and to assist in future vent determining locations.

future vent locations.

Reference 2 A follow-up No later than Basis provided Yes submittal to the 90 days in Reference 2.

nine-month following an response will be outage of provided to the sufficient NRC.

duration or 90 days following completion of RE-25.

Design, 6 NPPD will Same as above. Timeframe is Yes provide the CR consistent with evaluation/fix RIS 2005-020 results for the guidance and HPCI, CS, and corrective action RHR systems in process. Permits the follow-up final actions, if submittal.

necessary, to be taken during plant shutdown conditions.

Permits roll-up of results in the same report providing results of confirmatory walkdown results within primary containment.

NLS2008081 Attachment Page 13 of 17 Reference Items Not Schedule for Basis for Commitment Section Completed Completion Schedule (Yes or No)

Design, 9 The procedure March 3, 2009 Due date is Yes utilized for fill based CAP and vent of cross-prioritization.

tie piping will be updated by adding valve manipulations for flushing the piping to RW.

Design, 9 NPPD will revise Same as above.

Same as above.

Yes the fill and vent procedures to use UT to provide additional assurance the systems are filled.

NLS2008081 Attachment Page 14 of 17 Reference Items Not Schedule for Basis for Commitment Section Completed Completion Schedule (Yes or No)

Design, 9 Evaluate As established Same as above.

No And Testing improvements to by CAP.

Evaluation, 2 fill and vent and surveillance procedures reviewing flow rates to determine impact on gas accumulation. If

required, procedures will be changed to incorporate the review results.

Design, 9 Evaluate revising Same as above.

Same as above.

No engineering procedures to consider potential gas accumulation concerns and use of adequate high points.

Testing NPPD will revise March 3, 2009 Same as above.

Yes Evaluation, 2 surveillance procedures to use UT to provide additional assurance the systems are filled.

Testing Evaluation

1. Discussion of Periodic Venting or Gas Accumulation Surveillance Procedure Review Results:

A review was performed for surveillance procedures used for periodic venting or gas accumulation identification on the subject system piping susceptible to gas accumulation. These surveillance procedures provide assurance that the subject systems are purged of air and other non condensable gases.

2. Identification of Procedure Revisions or New Procedures:

No procedure revisions or new procedures are required to restore compliance with regulatory requirements.

NLS200808 1 Attachment Page 15 of 17 NPPD will revise surveillance procedures to use UT to provide additional assurance the systems are filled March 3, 2009.

NPPD will evaluate improvements to surveillance procedures reviewing flow rates to determine impact on gas accumulation. If required, procedures will be changed to incorporate the review results. This action is being tracked in CAP.,

3. Discussion on How Procedures Adequately Address the Manual Operation of the RHR System in its Decay Heat Removal Mode of Operation:

Prior to system operation, the CNS procedure for SDC requires the piping on both suction and discharge lines be vented and flushed via a positive pressure above atmospheric to remove potential gas accumulation. Reactor Pressure Vessel water level, temperature, and system response are monitored as directed by CNS procedures for proper operation.

4. Summarization of Procedure Review Results to Determine that Gas Intrusion Does Not Occur as a Result of Inadvertent Draining:

A review of industry historical documentation indicates that a majority of gas intrusion events resulted from maintenance recovery activities in support of ECCS maintenance windows. Loss of the keep fill system and the lack of a fill and vent procedure contributed to the accumulation of gas voids in ECCS systems. CNS conducts the fill and vent procedure as part of maintenance restoration to ensure that systems eliminate potential voids prior to turn over of the systems to Operations.

There was no impact to CNS procedures identified during the review associated with the GL 2008-01 response. Results of past procedure reviews based on previous industry documents are provided below:

INPO SER 02-05, Rev. 0 identified several fill and venting concerns which were addressed as procedure revision.

NRC IN 87-10 identified potential concerns with the use of suppression pool cooling and resulted in procedures revision.

Potential SDC Water Hammer was addressed by the Nuclear Steam System Supplier recommendations which resulted in NPPD implementing procedure revisions.

5. Description as to How Gas Voids are Documented and Trended, if Found:

CNS surveillance procedures have established criteria for documenting gas accumulation. When the criterion (air entrained water flow > -15 seconds) is exceeded, a CR is generated and entered into CAP for evaluation. CRs are trended as a part of the CAP Process.

Currently no established trending process has been established because of the variables in the venting process and a lack of precision in quantifying gas volume. In

NLS2008081 Attachment Page 16 of 17 order to meet this requirement in the future, the potential use of UT is being explored for volumetric estimation of gas accumulation.

6. Detailed List of Items that have Not Been Completed, a Schedule for Their Completion, and the Basis for that Schedule:

No procedure revisions or new procedures are required to restore compliance with regulatory requirements.

Actions to make procedure changes are being tracked as commitments. Actions to evaluate further if procedure changes are warranted have been entered into CAP. The specific schedule for completion will be prioritized by the CAP process.

Corrective Actions Evaluation

1. Summarization of Review Results of How Gas Accumulation has been Addressed:

CNS inputs identified discrepancies into CAP in accordance with 10 CFR 50 Appendix B, Criteria XVI. Where the piping did not meet the general walkdown requirements, a CR was written identifying a potential spot for gas accumulation.

The CR is then reviewed for operability by the Control Room staff and an operability determination is made based on the facts and supporting documentation. Where necessary, actions are taken in conjunction with the safety impact of the condition to correct the discrepancy. When little or no safety impact is determined the CR is further processed as prioritized by the CAP process.

During the conduct of walkdowns, CRs were written addressing potential gas voids in the systems.

2. Detailed List of Items that have Not Been Completed, a Schedule for Their Completion, and the Basis for that Schedule:

The CRs that have been entered into CAP received an initial evaluation that determined the impact on system operability. None of the identified conditions challenged operability of the systems. Based on that operability determination, actions taken on these systems will be done to improve the performance of the systems and preclude any future potential problems.

A follow-on evaluation is conducted on each CR within the programmatically driven time of one month from discovery. A plan to validate and address each item will be a part of that review. If further actions are required, the actions will be completed at the earliest opportunity not to exceed RE-25. In this manner, actions required to enhance system operation will be completed in a timely fashion. See Section 6 of the Design Evaluation segment of this attachment.

NLS2008081 Attachment Page 17 of 17 B. DESCRIPTION OF NECESSARY CORRECTIVE ACTIONS There are currently three open condition reports. See Section 6 of the Design Evaluation segment for additional discussion. At the present time, the actions are to evaluate and determine future vent locations, and to perform UTs for the individual conditions identified. No operability concerns have been identified.

C. CORRECTIVE ACTION SCHEDULE

1. Summarization of the Corrective Actions that Have Been Completed as a Result of the Evaluations Discussed Above:

There were no corrective actions completed in support of the GL. NPPD will provide the CR evaluation/fix results for the HPCI, CS, and RHR systems in the supplemental report.

2. Summarization of the Corrective Actions to be Completed:

There are three corrective actions resulting from the evaluation of the GL. NPPD will provide the CR evaluation/fix results for the HPCI, CS, and RHR systems in the supplemental report.

D. CONCLUSION NPPD has evaluated the accessible portions of those CNS systems that perform the functions described in GL 2008-01 and has concluded that these systems are Operable, as defined in the CNS TS and are in conformance to our commitments to the applicable General Design Criteria, as stated in the CNS USAR.

NPPD has concluded that the subject systems at CNS are in compliance with the TS definition of Operability, i.e., capable of performing their intended safety function and that CNS is currently in compliance with 10 CFR 50, Appendix B, Criterion III, V, XI, XVI and XVII, with respect to the concerns outlined in GL 2008-01 regarding gas accumulation in the accessible portions of these systems. Appropriate controls are in place to maintain compliance. As committed in Reference 2, NPPD will complete its assessments of those inaccessible portions of these systems during Refueling Outage 25 or an outage of sufficient duration, which ever comes first, and provide a supplement to this report with those results within 90 days from startup of that outage.

With respect to the inaccessible portions of the CNS systems within the scope of the GL, these systems have reasonable assurance of operability based on the justifications provided in Reference 2. NPPD has not identified any new information which changes the discussion nor the conclusions provided in Reference 2. Reference 3 allows NPPD to implement its proposed alternative course of action provided that implementation is consistent with associated requests discussed in Reference 3.

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© Correspondence Number: NLS2008081 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only and are not regulatory commitments. Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.

COMMITMENT COMMITTED DATE COMMITMENT NUMBER OR OUTAGE NPPD will evaluate the TSTF Traveler for making changes to individual licensee's TS related to the 90 days following potential for unacceptable gas accumulation, its NLS2008081-01 approval of the TSTF applicability to CNS, and evaluate adopting the Traveler Traveler to either supplement or replace the current TS requirements.

NPPD will incorporate industry guidance in regards NLS2008081-02 01/27/2009 to allowable suction void fraction.

NPPD will incorporate the industry guidance on establishing gas accumulation limits in the discharge NLS2008081-03 01/27/2009 piping of the effected ECCS systems.

NPPD will complete the necessary walk downs within CNS primary containment during the next At completion of outage of outage of sufficient duration or no later than the NLS2008074-01 sufficient duration or conclusion of RE-25, tentatively scheduled to completion of RE-25 commence Fall 2009.

90 days following an A follow-up submittal to the nine-month response outage of sufficient will be provided to the NRC no later than 90 days NLS200807402 duration or 90 days following an outage of sufficient duration or the following completion of completion of RE-25.

RE-25 NPPD will complete the follow-on evaluation of each CR within the programmatically driven time of one month from discovery. A plan to validate and address each item will be a part of that review. If NLS2008081-04 RE-25 further actions are required, the actions will be completed at the earliest opportunity not to exceed RE-25.

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@

Vents will be installed, as necessary, in the appropriate locations to facilitate gas accumulation NLS2008081-05 RE-25 removal.

NPPD will conduct UT of locations identified in the CRs to provide additional confirmation that HPCI, NLS2008081-06 02/27/2009 CS, and RHR are operable and to assist in determining future vent locations.

90 days following an NPPD will provide the CR evaluation/fix results for outage of sufficient the HPCI, CS, and RHR systems in the follow-up NLS2008081-07 duration or 90 days submittal.

following completion of RE-25 The procedure utilized for fill and vent of cross-tie piping will be updated by adding valve manipulations NLS2008081-08 03/03/2009 for flushing the piping to RW.

NPPD will revise the fill and vent procedures to use UT to provide additional assurance the systems are NLS2008081-09 03/03/2009 filled.

NPPD will revise surveillance procedures to use UT to provide additional assurance the systems are filled.

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