DCL-06-107, Supplemental Response to Requested Information Part 2 of NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors.

Supplemental Response to Requested Information Part 2 of NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors.

ML062560070
Person / Time
Site:	Diablo Canyon
Issue date:	09/01/2006
From:	Jacobs D Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-06-107, GL-04-002
Download: ML062560070 (6)

Text

Pacific Gas and Electric Company' Donna Jacobs Diablo Canyon Power Plant Vice President P.0. Box 56 Nuclear Services Avila Beach, CA 93424 805.545.4600 September 1,2006 Fax: 805.545.4234 PG&E Letter DCL-06-107 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units I and 2 Supplemental Response to Requested Information Part 2 of NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergqency Recirculation During Design Basis Accidents at Pressurized-Water Reactors"

Dear Commissioners and Staff:

This letter supplements Pacific Gas and Electric Company's (PG&E) initial response to Generic Letter (GL) 2004-02, Part 2, submitted by PG&E Letter DCL-05-099, "Response to Requested Information Part 2 of NRC Generic Letter 2004-02,

'Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors,"' dated September 1, 2005. In that letter PG&E stated that certain activities (e.g., confirmatory testing and analysis in support of resolving the issues raised by GL 2004-02) remained to be completed and that PG&E would submit a supplement addressing the open issues by September 1,2006.

As described in SECY-06-0078, dated March 31, 2006, the industry has been developing an understanding of certain aspects of chemical and coating behavior in a post loss-of-coolant accident environment and establishing an acceptable methodology for evaluating downstream effects. Those industry efforts are ongoing. Although testing and evaluation are not yet complete, PG&E has decided to modify or replace its existing recirculation sump screens and make additional debris reduction modifications. A schedule extension of approximately five weeks will be needed for Diablo Canyon Power Plant (DCPP) Unit 2. A request for extension will be submitted by separate correspondence. The DCPP Unit 1 modifications are currently planned to be implemented during the Spring 2007 refueling outage.

The enclosure provides the completion status and current completion dates for the open issues identified in DCL-05-099.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak 9 Diablo Canyon 9 Palo Verde

• South Texas Project e Wolf Creek

Document Control Desk PG&E Letter DCL-06-1 07 September 1,2006 Page 2 The NRC requested additional information in NRC Letter dated February 9, 2006, "Diablo Canyon Power Plant, Units 1 and 2, Request for Additional Information Re: Response to Generic Letter 2004-02, 'Potential Impact of Debris Blockage on Emergency Recirculation During Design-Basis Accidents at Pressurized-Water Reactor (TAC No. MC4682 and MC4683)."' PG&E will provide the requested additional information by separate correspondence in accordance with NRC Letter dated March 28, 2006, "Alternative Approach for Responding to the Nuclear Regulatory Commission Request for Additional Information Letter Re: Generic Letter 2004-02."

PG&E makes no regulatory commitments or revisions to regulatory commitments in this letter. If you have any questions or require additional information, please contact Stan Ketelsen at (805) 545-4720.

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

Executed on September 1,2006.

Donna rcobs jer/36643A Enclosure cc: Edgar Bailey, DHS Terry W. Jackson Bruce S. Malleft Diablo Distribution cc/enc: Alan Wang A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon *Palo Verde 9 South Texas Project

• Wolf Creek

Enclosure PG&E Letter DCL-06-107 Supplemental Response to Requested Information Part 2 of NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Press urized-Water Reactors" This enclosure provides a supplemental response to Requested Information Part 2 of NRC Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated September 13, 2004.

Pacific Gas and Electric Company (PG&E) submitted its initial response to GL 2004-02, Part 2, in PG&E Letter DCL-05-099, "Response to Requested Information Part 2 of NRC Generic Letter 2004-02, 'Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Press urized-Water Reactors,"' dated September 1,2005. Inthat letter PG&E stated that certain activities (e.g., confirmatory testing and analysis in support of resolving the issues raised by GL 2004-02) remained to be completed and that PG&E would submit a supplement addressing the open issues by September 1, 2006.

The open issues remaining on September 1, 2005, were summarized in DCL-05-099, Enclosure 1, in a table of corrective actions and a table of modifications showing target completion dates. These tables are reproduced below with the addition of a third column showing the current completion date, where applicable.

Status of Issues That Were Open on September 1,2005 (Reference DCL-05-099, Enclosure 1)

Corrective Action Description Target Current Completion Completion Date Date _ _ _ _ _ _ _ _ _ _

1. Finalize the analyses for December Unit I - 1R14'2

a. Debris generation, 31, 2005 Unit 2 - 2R14

b. Debris transport

c. Head Loss

d. Downstream effects,

e. Upstream effects

2. Revise the minimum sump level December Complete calculation (N-227, Revision 3), to 31, 2005 address minor discrepancies discovered during the review process. _______ _ _ _ _ _ _ _ _ _ _

2 Unit 2 Refueling Outage No. 14 scheduled to start Februar 40, 2008.

2 Unt Otag 2Refelig No 14schduld t strt ebrary4, 008

Enclosure PG&E Letter DCL-06-107 Corrective Action Description Target Current Completion Completion Date

____________________________ Date

3. Perform transport studies to reduce September 1, 10Z transport studies the amount of debris transported to 2006 have been determined the recirculation sump screens in not to be needed.

order to increase margin. During recent flume testing it was made Testing to determine evident that inorganic zinc (10Z) size distribution of readily sinks to the bottom of the test calcium silicate is flume and a substantial portion of complete.

the 10Z assumed to reach the screen in the transport analysis Testing to quantify would not be expected to reach the erosion characteristics recirculation sump screens. Also, for calcium silicate and perform testing to determine the size MariniteTM is distribution of calcium silicate scheduled to be insulation within the zone of completed by influence (Z01) and quantify erosion December 31, 2006.

characteristics for calcium silicate and MariniteTM insulation pieces that may be subjected to erosion within the transport pool.

4. Perform testing to demonstrate the April 1, 2006 Complete effectiveness and to refine the design of the debris interceptors.

Debris interceptors are required to reduce the debris that reaches the recirculation screen. _______

5. Conduct a test of coatings within the May 1, 2006 Complete ZOI. Atest is planned to be conducted by Wyle Laboratory as a sub-contractor to Westinghouse.

The purpose of the test is to demonstrate that the Z01 for coatings may be defined using a radius of 5D (5 times the diameter of the break pipe) versus the I OD as currently recommended in NEI 04-07.3 3Nuclear Energy Institute (NEI) 04-07, Volume 1, "Pressurized Water Reactor Sump Performance Methodology," and NEI 04-07, Volume 2, "Safety Evaluation by the Office of Nuclear Reactor Regulation Related to NRC Generic Letter 2004-02," Revision 0, dated December 2004.

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Enclosure PG&E Letter DCL-06-107 Corrective Action Description Target Current Completion Completion Date

_____________________________ Date

6. Update the head loss analysis to March 31, Unit 1 - 1R14 reflect the results of chemical effects 2006 Unit 2 - 2R14 head loss testing and analysis___________________

7. Submit a license amendment December A license amendment request for a change to the refueling 31, 2005 is not required. The water storage tank (RWST) revision to Calculation Technical Specification (TS) based N-277 showed the on Calculation N-227, if analysis RWST TS water level is indicates a higher water level is adequate.

necessary. RWST level is currently administratively maintained at a higher level than required by TS. _________________

8. Validate the structural capability of June 30, Unit 1 - 1R14 the sump 2006 Unit 2 -2R14

9. Update TS Bases 3.5.2.8 regarding IMarch 30, Unit 1 - 1R14 sump and trash rack inspections. 2006 Unit 2 - 2R14

10. Complete design, operational, and December Unit 1 - 1R14 procedural modifications. 31, 2007 Unit 2 - 2R14

11. Complete Region 2 analysis to July 1,2006 Unit 1 - 1R14' support use of NEI 04-07 Section 6 Unit 2 - Not applicable "Alternate Evaluation" methodology.

12. Perform confirmatory latent debris Unit 1 Complete sampling on Unit 1. Refueling Outage 13 (Fl05).

13. Implement Containment Latent December Unit 1 - I1R14 I Debris Assessment Program. 31, 2007 Unit 2 - 2R14 4Steam generators are scheduled for replacement during 2R14 and Unit I Refueling Outage No. 15 scheduled to start January 26, 2009, (1R1 5)resulting in a significant reduction in calcium silicate.

Use of "Alternate Evaluation" methodology will not be needed for Unit 2 and will be obviated for Unit 1 when it enters I RI5.

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Enclosure PG&E Letter DCL-06-107 Modification Description Target Revised Implementation Completion date Schedule

1. Modify the residual heat removal Unit 1 - Spring Unit 1 - IR14 suction inlet screen at.the 88-foot 2007 Unit 2 - Complete elevation. Unit 2 - Spring 2006

2. Relocate or modify the temporary Unit 1 - Spring Cancelled.

storage rack in the containment 2007 Computational annulus (to reduce debris transport). Unit 2 - Spring fluid dynamics 2006 analysis shows rack does not block flow.

3. Modify the reactor cavity door and Unit 1 - Spring Unit 1 - 1R14 curb (to allow more debris to be 2007 Unit 2 - Complete trapped in the reactor cavity inactive Unit 2 - Spring Note: curb sump). 2006 modification is not needed at this

___ ____ ___ time.

4. Add two, approximately 18-inch high, Unit 1 - Spring Design changed perforated plate debris interceptors at 2007 to one interceptor the entrances to the labyrinth Unit 2 - Spring in Door 277.

walkway leading to Door 277 in the 2006 Unit 1 - 1R14 crane wall (to capture reflective metal Unit 2 - 2R14 insulation and unqualified coating paint chips).

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