ML18153D011
| ML18153D011 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/12/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18153D010 | List: |
| References | |
| NUDOCS 9205220246 | |
| Download: ML18153D011 (6) | |
Text
1.0 INTRODUCTION
e
- e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION STATION BLACKOUT RULE (10 CFR 50.63)
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION. UNITS 1 AND 2 DOCKET NOS. 50-280/281 The NRC staff's Supplemental Safety Evaluation (SSE) pertaining to the responses of the Virginia Electric & Power Company (the licensee) to the staff's Safety Evaluation (SE) regarding the Station Blackout (SBO) Rule, 10 CFR 50.63, for the Surry plant was transmitted to the licensee by letter dated December 6, 1991.
The staff's SSE found the licensee's proposed method of coping with an SBO to be acceptable subject to the satisfactory resolution of several open items.
The licensee responded to the staff's SSE and, specifically, to the open items by letters from W. L. Stewart, dated February 10 and March 17, 1992.
2.0 EVALUATION The licensee's responses to the staff's SSE are evaluated below.
2.1 Station Blackout Duration {SSE Section 2.1)
SSE Evaluation:
In the SSE, the staff concluded that the SBO duration should be 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> (based on an EOG target reliability of 0.95, an independence of offsite power group of I3, an offsite power design characteristic of P2, and an EAC power configuration of C) rather than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> as determined by the licensee.
Licensee Response:
The licensee stated that it believed that it had correctly classified the independence of offsite power group as Il/2, resulting in an offsite power design characteristic of p2* and a coping duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
9205220246 920512 PDR ADOCK 05000280 P
PDR Using Table 5 of RG 1.155, the licensee concludes that since the switchyards at Surry are electrically independent, the analysis starts in matrix block 11 of Table 5, and the "or" in that column means that Surry meets the 11 classification without further consideration of any bus transfer schemes that occur at Surry.
Staff Evaluation:
When Column 1 of Table 5 of RG 1.155 is interpreted in the manner applied by the 1 icensee, it is clear that the "or" is -meant to be an "and," otherwise the remainder of the Table 5 column under the "or" would never apply and therefore would not be needed.
Also, using the licensee's rationale, any plant having electrically isolated switchyards would satisfy the 11 criteria even if it had no automatic or manual bus transfers schemes for the Class IE buses.
Table 5 of RG 1.155 is based on NUREG-1032.
Although Table 5 can be misin~erpreted based on its wording alone, it is clear from NUREG-1032 that the correct application of Table 5 is to proceed to Row 2 which analyzes the automatic and manual transfer schemes for the Class IE buses.
For Surry, Row 2.a. is applicable, i.e., the normal source of power is the unit main*
generator. Also, based on Table A.3 of NUREG-1032, the intent of paragraphs 2.a.(l) and (2) of Table 5 of RG 1.155 is that an Il classification requires two automatic transfers of all safety buses.
This is not applicable for Surry; however, Paragraph B.2.b of Table A.2 of NUREG-1032 is applicable.
This places Surry in an I2 category (Table A.3).
Therefore, the staff agrees that the Surry classification is Il/2, resulting in an offsite power group P2*
and a coping duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
Also, the staff has relaxed the 0.975 EOG target reliability to 0.95 based on the installation of two diesel generators (DGs) and their connectability characteristics at Surry.
2.2 Proposed AAC Power Source (SSE Section 2.2)
SSE Evaluation: In the SSE, the staff found the licensee's proposed addition of two non-safety DGs as an AAC power source to be acceptable.
However, the staff stated that the licensee should provide confirmation that the proposed AAC power source meets the other criteria of Appendix B of NUMARC 87-00, specifically items B.8, B.9, B.10, B.11, B.12, B.13, and RG 1.155, Position C.3.3.5.5.
The staff also stated that the licensee should confirm that each day tank will be sized to allow the diesel to run for the SBO duration of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
The staff found the use of the existing automatic load sequencing acceptable provided the licensee demonstrates by test that the SBO equipment can be powered from the AAC source within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
However, the staff found that the automatic connection of the AAC DG to a pre-selected emergency bus as unacceptable.
. :('
e Licensee Response:
The licensee stated that the AAC sources are planned to meet the applicable criteria specified in NUMARC 87-00 Appendix Band described in detail how the AAC power source will meet the criteria of items B.8 through B.13 of Appendix B of NUMARC 87-00, and stated that the reliability program is in general accordance with RG 1.155, Position C.3.3.5.5.
The licensee stated that the proposed design will provide the automatic alignment of one of the AAC sources to the E transfer bus and the other AAC source to the F transfer bus.
Once the diesels are aligned to the transfer buses, they will be manually aligned to one of the emergency buses in each unit.
The licensee noted that the day tank, which would be required for 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> operation, may be larger than acceptable based on insurance and other considerations, and is not as desirable as using a shorter duration and therefore a smaller tank.
Staff Evaluation:
The staff has reviewed the licensee's discussion of how the proposed AAC source will meet the criteria of items B.8 through B.13 of Appendix B of NUMARC 87-00 and finds it acceptable.
The staff has accepted the 4-hour coping duration (see Section 2.1 above) so the issue regarding the 8-hour day tank is resolved.
2.3 Compressed Air (SE Section 2.3.3, SSE Section 2.5)
SSE Evaluation:
In the SSE, the staff reported that the compressed air capacity was still under review; therefore the staff found this issue to be an open item.
Licensee Response:
The licensee stated that instrument air will be made available to the atmospheric stea~ dump valves from a source other than air bottles and that there are several options available to Surry Power Station in providing instrument air during an SBO.
At present the licensee plans to d*evelop station procedures to power a normal bus feeding either one of the two station air compressors.
Staff Evaluation: Based on its review, the staff finds the licensee's response acceptable.
Therefore, the staff considers this SSE issue resolved, provided that the licensee will have procedures to power a normal bus feeding either one of the two station air compressors during an SBO event.
2.4 Effects of Loss of Ventilation (SSE Section 2.6)
SSE Evaluation:
In the SSE, the staff indicated that based on its review and its concerns related to the initial temperatures used in the heat-up analysis for the control room complex and the emergency switchgear room (ESGR) complex, and the absence of a procedural commitment to open control cabinet doors during an SBO event, the staff had not been able to conclude that the licensee's analyses of the effects of loss of ventilation in the control room complex and the ESGR complex were acceptable.
The staff considered that the issue with respect to the effects of loss of ventilation at the Surry plant was not fully resolved; therefore, the issue was identified as an open item.
.. ~
.j Licensee Response:
In the response, the licensee indicated that it will commit to providing a 10 minute AAC power source and conducting a test to demonstrate that the AAC source is available to power the shutdown buses within 10 minutes after the operator has ascertained that an SBO condition exists and that the emergency DGs cannot be started.
Staff Evaluation:
Based on its review and provided that the AAC power source will have sufficient capacity to power the HVAC equipment for the control room complex and the emergency switchgear room complex, this issue becomes moot and no commitments on initial temperature are necessary.
The staff considers this issue resolved.
2.5 Proposed Modifications (SSE Section 2.9}
SSE Evaluation:
In the SSE, the staff stated that it considers the 5-year time frame to complete the modifications and procedures as excessive.
The
. licensee should implement the changes within 3 years, or provide a detailed justification as to why a longer time frame is required.
The justification should include a detailed schedule of the different phases of the project.
Also, the licensee should consider the receipt of this SSE as the starting ti me, s i nee the staff has accepted the proposed AAC source..
Licensee Response:
The licensee presented a detailed schedule consisting of seven main phases and provided detailed justification for a 5-year completion schedule.
In particular, the licensee noted that the tie-ins to the D, E, and F transfer buses must be properly sequenced since one offsite source to at least one emergency bus is disabled during any transfer outage.
Further, only one transfer should be worked per any given outage due to the significant testing required and to minimize operator confusion.
The schedule provides for the installation of the first AAC diesel prior to the September 1994 Unit 2 outage, and the second AAC diesel prior to-the 1995 Unit 1 outage.
The licensee noted that partial compliance can be achieved by the end of the Unit 2 1994 refueling outage and 1995 Unit 1 refueling outage since bus lJ or 2H can be powered by the AAC source, thus assuring that an SBO on either unit can be mitigated.
The final tie-in to the D bus and associated testing (allowing the other division safety buses lH and 2J to be powered by the AAC source) would be completed by December 1995.
Staff Evaluation:
The staff has reviewed the licensee's proposed procurement, installation and testing schedule *and agrees that these activities could not be realistically completed prior to the September 1994 Unit 2 refueling outage.
The staff also accepts licensee's rationale that in the interest of safety the tie-in of the AAC sources to the transfer buses should be sequenced and carefully coordinated. Thus, the staff finds the licensee's proposed schedule to be acceptable.
..'t
e 2.6 Quality Assurance (QA) and Technical Specifications (TS)(SSE Section 2.10)
SSE Evaluation:
In the SSE, the staff recommended that the licensee should verify that the SBO equipment is covered by an appropriate QA program consistent with the guidance of RG 1.155.
Licensee Response:
In response to the above staff concern, the licensee stated that the nonsafety systems and equipment being relied upon to meet the requirements of the SBO Rule will be included in a QA program, which meets the requirements of RG 1.155 Section 3.5, and Appendices A and B.
The inclusion of the SBO equipment in a QA program which governs their associated design, specification, and testing activities in addition to the development and maintenance of a periodic testing program with trending and root cause evaluation (as discussed below) should be adequate to assure their proper operation; therefore, there is no need to apply TS to the SBO equipment.
The licensee further stated that the position is further reinforced by the fact that SBO is not considered as a design basis event (DBE).
Documentation standards for equipment operability are not to be as rigorous as are typically required to meet the design basis requirements of 10 CFR 50.49, and suitable independence will exist between the SBO equipment and the safety-related systems required to respond to a DBE, such that there is no anticipated potential for common cause failure.
Staff Evaluation:
The staff finds the licensee's response pertaining to QA to be acceptable.
With respect to the TS, TS for the SBO equipment are currently being considered by the NRC in the context of the Technical Specification Improvement Program.
If the staff later determines that TS for the SBO equipment is warranted, the licensee will be notified of the implementation requirements.
2.7 Emergency Diesel Generator (EDG) Reliability Proq~am (SSE Section 2.11)
SSE Evaluation:
In the SSE the staff stated that an EDG reliability program should be developed in accordance with the guidance of RG 1.155, Section 1.2.
Licensee Response:
In response to the staff's concern, the licensee described its reliability program and stated that it is consistent with the guidelines of NUMARC 87-00, Appendix D.
The licensee noted that the resolution of Generic Issue B-56, "Emergency Diesel Generator Reliability" is currently under consideration and review within the NRC and industry.
The licensee stated that it will continue to review its reliability program as required, however, it would not make commitments relative to RG 1.155 at this time.
Staff Evaluation:
The reliability program described by the licensee appears to follow the guidelines of Generic Issue B-56 which has not been approved by the NRC.
Therefore, in the meantime the licensee is required to commit to an EDG reliability program which, as a minimum, contains the five items of RG 1.155, Section 1.2.
..'t'
e e 3.0
SUMMARY
AND CONCLUSION The staff has reviewed the licensee's responses to the staff's December 6, 1991, SSE pertaining to the SBO Rule (10 CFR 50.63) for the Surry Power Station, Units 1 and 2.
The staff finds the licensee's responses to be acceptable except that until Generic Issue B-56 is resolved, the licensee needs to commit to an EDG reliability program which, as a minimum, contains the five elements of RG 1.155, Section 1.2.
Principal Contributor:
A. Toalston Date:
May 12, 1992
.. '~