NLS2006068, Response to Request for Additional Information Regarding License Amendment Request for a One-Time Extension of the Integrated Leakage Rate Test Interval
| ML062480040 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 08/29/2006 |
| From: | Edington R Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2006068 | |
| Download: ML062480040 (7) | |
Text
N Nebraska Public Power District Always there when you need us-NLS2006068 August 29, 2006 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Response to Request for Additional Information Regarding License Amendment Request for a One-Time Extension of the Integrated Leakage Rate Test Interval Cooper Nuclear Station, Docket No. 50-298, DPR-46
References:
- 1.
Letter from Brian Benney, U.S. Nuclear Regulatory Commission, to Randall K. Edington, Nebraska Public Power District, dated August 15, 2006, "Cooper Nuclear Station - Request for Additional Information Re: Request for a One-Time Extension of Containment Integrated Leakage Rate Test Interval" (MC9732)
- 2.
Letter from Randall K. Edington, Nebraska Public Power District, to U.S. Nuclear Regulatory Commission, dated January 30, 2006, "License Amendment Request for a One-Time Extension of Containment Integrated Leakage Rate Test Interval" (NLS2006002)
The purpose of this letter is for the Nebraska Public Power District (NPPD) to submit a response to the Nuclear Regulatory Commission (NRC) Request for Additional Information (RAI) sent by NRC letter dated August 15, 2006 (Reference 1). In Reference 1 the NRC indicated this information is needed to complete their review of the NPPD license amendment request for a one-time extension of the Integrated Leakage Rate Testing interval for the Cooper Nuclear Station, submitted by letter dated January 30, 2006 (Reference 2). The response to the RAI is provided in the attachment.
The information submitted by this RAI response does not change the evaluation of No Significant Hazards Consideration submitted by the Reference 2 letter.
Should you have any questions regarding this submittal, please contact Paul Fleming, Licensing Manager, at (402) 825-2774.
COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com
NLS2006068 Page 2 of 2 I declare under penalty of perjury that the forgoing is true and correct.
Executed on August 29, 2006 Sincerely, Randall K. Edington Vice President-Nuclear and Chief Nuclear Officer
/rr Attachment cc:
Regional Administrator *v/ Attachment USNRC - Region IV Cooper Project Manager w/ Attachment USNRC - NRR Project Directorate IV-I Senior Resident Inspector w/ Attachment USNRC-CNS Nebraska Health and Human Services w/ Attachment Department of Regulation and Licensure NPG Distribution w/o Attachment CNS Records w/ Attachment
NLS2006068 Attachment Page 1 of 4 Attachment Response to Request for Additional Information Regarding License Amendment Request for One-Time Extension of the Integrated Leakage Rate Test Interval Cooper Nuclear Station, Docket No. 50-298, DPR-46
Reference:
Letter from Brian Benney, U.S. Nuclear Regulatory Commission, to Randall K. Edington, Nebraska Public Power District, dated August 15, 2006, "Cooper Nuclear Station - Request for Additional Information Re: Request for a One-Time Extension of Containment Integrated Leakage Rate Test Interval" (MC9732)
I. NRC Request lIE-1240 requires licensees to identifj, the containnment suiface areas requiring augmented examinations. Provide the locations of the steel containment sumtfaces that have been identified as requiring augmented examination and a sumnmary of the findings of the examinations pemformed.
NPPD Response The Cooper Nuclear Station (CNS) Containment Inspection Program identifies the wetted surface of the suppression pool (Torus) as the only area requiring augmented examination.
It is visually examined once each inspection period. VT-I examinations are performed in accordance with ASME Sectigon XI, 1992 Edition, 1992 Addenda.
These examinations were performed during outages in March 2001 (period 1) and January 2005 (period 2). Pitting was observed in both examinations, primarily around the piping penetrations. Pits depths exceeding pre-established examination criteria were evaluated.
None of the pits exceeded the design code allowable for maximum pit dejlth. Areas of pitting were recoated with an underwater epoxy coating to minimize subsequent pitting and corrosion.
Additional examinations of the remaining bays of the torus were performed in accordance with 10 CFR 50.55a, Codes and Standards, Section 50.55a(b)(2)(ix)(D), as an alternative to 1WE-2430. The remaining bays exhibited similar or lesser levels of degradation from pitting. Preservice VT-I visual examinations were performed on the recoated areas. The results of these examinations were acceptable.
NLS2006068 Attachment Page 2 of 4
- 2. NRC Request For the examination ofpenetration seals and gaskets, and e.xamination and testing of bolted connections associated with the primamy containment pressure boundaiy, the licensee requested relief fiom the requirements of the code. As an alternative, the licensee proposed to examine the above items duitng the leak-rate testing of the prima,'
containment. Option B of Appendix Jfor Type B and Type C testing (peo" Nuclear Energy Institute ('NEI) 94-01 and Regulatory Guide (RG) 1.163), and the integrated leakage rate test extension requested in this amendment for Type A testing, provide flexibilit, in the scheduling of these inspections. Discuss your schedule for examination and testing of seals, gaskets, and bolted connections that provide assurance regarding the integrity of the containment pressure boundai-,.
NPPD Response As an alternative to examination, the leak-tightness of seals and gaskets is tested through local leakage rate test (LLRT) pursuant to IOCFR50, Appendix J, in accordance with Relief Request RC-02. (The Nuclear Regulatory Commission documented their approval of Relief Request RC-02 in letter from John N. Hannon to G. R. Horn, Nebraska Public Power District, dated November 18, 1998). For those penetrations that are routinely disassembled during refueling outages, a LLRT is required upon final assembly and prior to start-up. For example, the leak tightness of seals, gaskets, and bolting, associated with containment equipment hatches, airlocks, and drywell head that are opened during an outage, are verified by a LLRT. For seals and gaskets that are not routinely disassembled, the frequency of LLRT is based on past performance, and may be on a frequency up to once every ten years.
The allowance for increasing test intervals and justification for extending Type B test intervals to ten years is presented in sections 10.2.1.2 and 11 of NEI 94-01, "Industry Guideline for Implementing Performance-Based Option of 10 CFR Part 50, Appendix J."
NEI 94-01 was endorsed by the NRC in Regulatory Guide 1.163, "Performance Based Containment Leak-Test Program," dated September 1995. Currently, CNS performs LLRTs at intervals of no greater than once every 60 months.
Containment bolted connections that are disassembled during the course of normally scheduled work activities receive a VT-I visual examination as required by Table IWE-2500-1, Item E8.10. Flaws or degradation identified during the VT-I examination are reviewed by the Inservice Inspection Program Engineer and the Authorized Nuclear Inservice Inspector. Conditions exceeding allowable standards are entered into the Corrective Action Program for resolution.
NLS2006068 Attachment Page 3 of 4 The alternative LLRT and current practice of containment bolted connection examination provide continued assurance regarding integrity of the containment pressure boundary.
- 3. NRC Request Inspections of some steel containment strutctures have identified degradation of uninspectable areas (gap between the shield wall and dqywell). These degradations cannot be found b), visual (i.e., VT-1 or VT-3) examinations unless the), are through the thickness of the shell or when 100 percent of the uninspectable suifaces are periodically, examined by ultrasonic testing. Discuss what approach is used in the Cooper Nuclear Station (CNS) to identify degradation of uninspectable areas of the containment.
NPPD Response The few instances of Mark I containment external corrosion events are plant specific and not generic to the containment design. Based on CNS experience and that of our peers, the drywell shell at CNS would be susceptible to degradation only if significant chronic leakage is present. The degradation would be exacerbated if the sand cushion drains are plugged. If it can be shown that neither of these two events has occurred, it is reasonable to conclude that degradation has not occurred, and therefore, further effort to identify degradation in inaccessible areas of containment is not needed.
One area of the drywell that is inaccessible for examination is the air gap between the steel shell and concrete shield wall. The only source of water into this air gap is the reactor cavity when flooded during refueling outages. One method of introducing the water from the flooded reactor cavity into this area is failure of the refueling bellows.
Leakage through the refueling bellows, or any other source, would result in moisture in, the inaccessible air gap that will continue down directly to the sand cushion area. Sand cushion drain lines route any leakage into the air gap away from the drywell shell. These drain lines are monitored for leakage whenever the reactor cavity is flooded. Monitoring of the sand cushion drains has not detected moisture that could potentially corrode the exterior of the containment. CNS has not experienced any leakage of the refueling bellows that could introduce water to the exterior of the containment. The sand cushion drain lines have been previously confirmed to not be plugged. In addition, the CNS drywell exterior received a protective coating that provides additional assurance of corrosion protection. Based on this experience the exterior has not been selected for augmented examinations.
During CNS operation primary containment is inerted with nitrogen to maintain oxygen concentration within technical specification (TS) limits. This results in the containment being maintained at a slightly positive pressure. Primary containment pressure is continuously recorded in the Control Room and verified by TS surveillance on a
NLS2006068 Attachment Page 4 of 4 frequency of once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Degradation that results in a loss of primary containment integrity would be indicated by a drop in pressure in primary containment or by an increase in the nitrogen makeup flow rate. An increase in the rate of nitrogen makeup to containment would be detected and investigated. The fact that the containment is continuously pressurized by the containment inerting system, and is periodically monitored, provides assurance that gross containment leakage that may develop during power operation as a result of significant degradation of the containment will be detected.
- 4. NRC Request In response to GL 87-05, Cooper committed to inplement new surveillance procedures for inspection of sand cushion drains during refueling outages. Discuss the results obtained firon the inspection.
NPPD Response Procedures to monitor the sand cushion drain lines for leakage were prepared and implemented at CNS. The first performance of monitoring these drain lines was during April and May of 1989. The sand cushion drain lines are monitored for water leakage daily when the reactor cavity is flooded during outages. No leakage has been detected.
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© Correspondence Number: NLS2006068 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 None
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