ML071380508
| ML071380508 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/29/2007 |
| From: | Michael Scott NRC/NRR/ADES/DSS/SSIB |
| To: | Marinos E NRC/NRR/ADRO/DORL/LPLII-1 |
| Architzel R, NRC/NRR/DSS/SSIB, 415-2804 | |
| References | |
| GL-04-002 | |
| Download: ML071380508 (5) | |
Text
May 29, 2007 MEMORANDUM TO:
Evangelos C. Marinos, Chief, Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Michael L. Scott, Chief
/RA/
Safety Issue Resolution Branch Division of Safety Systems Office of Nuclear Reactor Regulation
SUBJECT:
OCONEE NUCLEAR STATION DRAFT OPEN ITEMS FROM STAFF AUDIT OF CORRECTIVE ACTIONS TO ADDRESS GENERIC LETTER 2004-02 Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors, requested that all pressurized-water reactor licensees (1) evaluate the adequacy of the emergency sump recirculation function with respect to potentially adverse effects associated with post-accident debris, and (2) implement any plant modifications determined to be necessary. Duke Energy Corporation, the licensee, has conducted an evaluation of re-circulation sump performance for the Oconee Nuclear Station, and is conducting significant modifications, including installation of new re-circulation sump strainers at all three units.
The staff conducted a detailed audit of the new sump design and associated analyses, evaluations, testing and modifications for Oconee Nuclear Station during the week of March 26, 2007. This audit was an in-process snapshot of Duke Energys GL 2004-02 corrective actions, which are to be completed by December 31, 2007. This is one of several audits to be conducted over an approximate two-year period to establish a sample basis to assist in verifying the adequacy of pressurized-water reactor licensee corrective actions to address GL 2004-02.
This memorandum transmits the draft open items from the audit. These draft open items are subject to change as the audit report is developed, finalized and issued. Please note that the audit report will contain no conclusion as to the overall adequacy of the licensees GL 2004-02 corrective actions. That conclusion will be reached when the final GL 2004-02 response (requested by December 31, 2007) is reviewed. That response is expected to respond to the CONTACT:
Ralph Architzel, SSIB/DSS (301) 415-2804 Joe Golla, PGCB/DPR (301) 415-1002 audit report open items, as well as generic requests for additional information issued to the licensee in 2006, and will describe the finalized GL 2004-02 corrective actions for Oconee Nuclear Station.
Docket Nos:
50-269, 50-270, and 50-287
Enclosure:
As stated audit report open items, as well as generic requests for additional information issued to the licensee in 2006, and will describe the finalized GL 2004-02 corrective actions for Oconee Nuclear Station.
Docket Nos:
50-269, 50-270, and 50-287
Enclosure:
As stated CONTACT:
Ralph Architzel, SSIB/DSS (301)415-2804 Joe Golla, PGCB/DPR (301)415-1002 DISTRIBUTION: PUBLIC SSIB R/F JGolla LOlshan ADAMS Acession Number: ML071380508 NRR-106 OFFICE DSS/SSIB BC:DCI/CSGB BC:DSS/SSIB NAME RArchitzel AHiser MScott DATE 5/23/07 5/23/07 5/29/07 OFFICIAL RECORD COPY
Draft Open Items for March 2007 Audit of Oconee Nuclear Station Corrective Actions for Generic Letter 2004-02 Open Item: Potential for Blockage or Obstruction of Drainage Flow Paths The licensee did not provide sufficient information for the staff to conclude that water hold up in the refueling canal and reactor cavity volumes due to debris blockage of drainage flowpaths would not be a concern for Oconee Nuclear Station. The staff noted that the licensee should consider the potential for these flowpaths to be blocked both by (1) one or more large pieces of debris and (2) an accumulation of smaller pieces of debris.
Open Item: Latent Debris Sample Size The staff considered the number of latent debris samples taken by the licensee, at four locations within Unit 3 containment, to be inadequate for obtaining a sufficiently accurate estimate of containment latent fibrous and particulate debris masses, given the spectrum of debris buildup conditions on various containment surfaces.
Open Item: Unjacketed fibrous insulation erosion The licensee identified that there are some piping runs and elbows insulated with unjacketed fibrous materials in containment. The licensee had not evaluated the effect of erosion of such fibrous insulation induced by containment spray drainage.
Open Item: Potential for drainage path blockage as a result of containment washdown The licensees procedures do not contain adequate precautions to ensure that containment washdowns do not result in debris entering and clogging fluid drainage paths in the containment upstream of the strainers.
Open Item: Water hold up effect on Minimum Water Level The licensee did not consider two sources of water holdup that could reduce the calculated water level. These sources include (1) holdup of spray water droplets in the containment atmosphere, and (2) holdup of water as condensate film on surfaces of the containment.
Open Item:
Justify Coatings Visual Assessment The licensee relies on visual inspection as part of their qualified coatings assessment program.
The use of visual inspection to adequately identify degraded qualified coatings has been challenged by the staff. At the time of this audit the industry had not verified that visual assessment was an acceptable method for identifying degraded qualified coatings.
Open Item:
Downstream Effects-Core Blockage Although downstream evaluations were in progress during the audit, the licensee has not made any final conclusions as to whether the cores at Oconee could be blocked by debris following a LOCA, and this area is incomplete.
Open Item:
Downstream Effects Evaluations Preliminary The licensee evaluations of the downstream effects of debris on systems and components are preliminary; based in part on the generic methodology of WCAP-16406-P which is under review by the NRC staff. Conclusions and findings of the staff review need to be applied to the Oconee Nuclear Station evaluation of post-LOCA downstream effects.
Open Item: Mission times for Fluid Systems The mission times for high pressure injection, low pressure injection, and reactor building spray were defined as 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, 30 days and 7 days, respectively. The licensee did not provide a clearly defined basis or supporting documentation for these mission times.
Open Item:
Quantification and assessment of downstream effects that cause seal leakage The licensee did not quantify seal leakage associated with downstream effects into the auxiliary building, nor evaluate the effects on equipment qualification, sumps and drains operation or room habitability.
Open Item: Evaluate Chemical Effects The licensee's chemical effects analysis was in progress at the time of the audit. Until the licensee completes the chemical effects analysis and chemical effects head loss testing, chemical effects will remain an open item.
Open Item:
Evaluation of the contribution of coatings to chemical effects The licensee had not evaluated the contribution of coatings to chemical effects by: (1) leaching constituents that could form precipitates or affect other debris; and (2) changing form due to the pool environment.