NLS2006045, Response to Request for Additional Information Regarding License Amendment Request for a One-Time Extension of the Integrated Leakage Rate Test Interval
| ML061420155 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/17/2006 |
| From: | Edington R Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2006045, TAC MC9732 | |
| Download: ML061420155 (7) | |
Text
N Nebraska Public Power District Always there when you need us NLS2006045 May 17, 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 April 18, 2006, "Cooper Nuclear Station - Request for Additional Information Re: One-Time Extension of the Integrated Leakage Rate Test" (TAC No. 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 to submit a response to the Nuclear Regulatory Commission (NRC) Request for Additional Information (RAI) sent to Nebraska Public Power District (NPPD) by letter dated April 18, 2006 (Reference 1). In Reference I the NRC indicated this information is needed to support 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.
Should you have any questions regarding this submittal, please contact Paul Fleming, Licensing Manager, at (402) 825-2774.
COOPER NUCLEAR STAON P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com
NLS2006045 Page 2 of 2 I declare under penalty of perjury that the forgoing is true and correct.
Executed on 7/7 6
(Date)
Randall K. Edington
/
Vice President-Nuclear and Chief Nuclear Officer
/rr Attachment 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 NPG Distribution w/o Attachment CNS Records w/ Attachment
NLS2006045 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, DPR46
Reference:
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)
I. NRC Request The analysis of external events in Appendix B of the January 30, 2006, submittal presents the estimated delta large early release frequency (ALERF) associated with extending the test frequencyfrom one test in 10years to one test in 15years. Please provide the estimated ALERF (for combined internal and external events) associated with extending the test frequency from the original three tests in 10 years to one test in 15 years (using the Nuclear Energy Institute Interim Guidance.)
NPPD Response The following Table I provides a bounding estimate of ALERF (LERF increase) for combined internal and external events associated with extending the test frequency from the original three tests in 10 years to one test in 15 years using the Nuclear Energy Institute (NEI) Interim Guidance.
The method used in Table I and Appendix B of the January 30, 2006 submittal provided a bounding external event LERF increase by counting the full estimated seismic and fire Core Damage Frequency (CDF) against the 3b Electric Power Research Institute (EPRI) Accident Class (Large Isolation Failures) frequency.
The results of Table 1 indicate that when the internal and bounding external events LERF increase contributions are summed, the total bounding estimated increase in LERF is 4.08E-07/yr. This increase is in the range of I E-07/yr to I E-06/yr; therefore calculation of total LERF is performed to show that it remains less than I E-05/yr (Region II of Regulatory Guide (RG) 1.174 Figure 4, Acceptance Guidelines for LERF).
NLS2006045 Attachment Page 2 of 4 TABLE 1: CALCULATION OF LERF INCREASE USING NEI INTERIM GUIDANCE 3b Frequency LERF Increase Probabilistic Risk 3b Frequency (3-(1-per-15year (3-per-10 to I-Assessment Element per-10 year ILRT)
ILRT) per-15)
Bounding External Events 1.OOE-07 5.02E-07 4.07E-07 Internal Events 1.58E-09 7.90E-09 6.32E-09 Combined (Internal +
Bounding External) 1.02E-07 5.1OE-07 4.08E-07 Table 2 provides the estimated Total LERF (for combined internal and external events) associated with extending the test frequency from the original three tests in 1O years to one test in 15 years using the NEI Interim Guidance. Two cases were examined in table 2:
- Case I calculates the external event Base LERF assuming the fractional contribution of external event CDF is the same as the internal event fraction.
- Case 2 calculates the external event Base LERF assuming IO% of the external event CDF contributes to LERF.
From Table 2, the results for both sensitivity cases indicate that when the internal and external events contributions are summed, the total bounding estimated LERF is 4.69E-06/yr.
This is within the acceptance guidelines for Region 11 of RG 1.174 Figure 4.
TABLE 2: CALCULATION OF TOTAL LERF IINTERNAL+EXTERNALI Base CDF (Internal) 1.30E-05 Base CDF (External) 3.72E-05 Base LERF (Internal) 5.60E-07 Case 1: LERF Split Fraction Based on Internal Events Base LERF (External) 1.60E-06 Base LERF (Internal+ External) 2.16E-06 Total LERF [(Internal+ External), (Base LERF + ALERFj)]
2.57E-06 Case 2: LERF Split Fraction Based on 10% of CDF Base LERF (External) 3.72E-06 Base LERF (Internal+ External) 4.28E-06 Total LERF [(Internal+ External), (Base LERF + ALERF)]
4.69E-06 Realizing the conservatism contained in the ALERF calculated by assuming 100% of the external event CDF contributes to EPRI class 3b frequency, a sensitivity calculation was performed for ALERF assuming the external event CDF contribution equals the internal event fraction for class 3b.
NLS2006045 Attachment Page 3 of 4 From Table 9-1 of the enclosure to the January 30, 2006 submittal, approximately 0.0 1% of CDF contributed to the internal events class 3b frequency. Assuming approximately 0.0 1%
of the external event CDF contributes to the EPRI class 3b frequency results in an estimate of 2.44E-8/yr ALERF (LERF increase) for combined internal and external events associated with extending the test frequency from the original three tests in 10 years to one test in 15 years using the NEI Interim Guidance. This shows the bounding nature of the ALERF calculated in Table 1 and Appendix B of the January 30, 2006 submittal.
- 2. NRC Request Clarify whether the baseline LERF value of 5.60E-7/year, reported in Appendix B, is based on internal events only, or internal and external events. If the former, provide the total LERF for internal and external events, including the impacts of the requested change.
NPPD Response:
The LERF value of 5.6E-07/yr is based on internal events only. The total LERF for internal and external events, including the impacts of the requested change, is provided in the response to Request for Additional Information Question No. 1.
- 3. NRC Request Reconcile the low baseline LERF value of S. 60E-7/year reported in Appendix B with the much higher early containmentfailurefrequency of 5.49E-6/year, reported in Table 6-S of the Enclosure to the January 30, 2006, submittal.
Describe the definition ofLERF used in the Cooper probabilistic risk assessment, and provide an accounting of how the major sequences contributing to internal and external event core damage frequency are classified (as LERF and non-LERF) using this definition.
NPPD Response:
A large early release from containment is defined as a radionuclide release of sufficient magnitude to have the potential to cause early fatalities and occurs in less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> following declaration of General Emergency, typically when minimal offsite protective measures have been accomplished. Using site-specific thermal-hydraulic calculations, this is interpreted as fractional release of CsI compound exceeding 10% of core inventory in less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the expected Emergency Action Level requiring General Emergency and evacuation.
NLS2006045 Attachment Page 4 of 4 Many of the early containment failure modes do not result in a large early release. The LERF frequency of 5.6E-07/year is comprised of early containment failure modes that result in a large release (e.g., releases through the drywell without the benefit of wetwell scrubbing). The values of release frequency reported in Table 6-5 of the enclosure to the January 30, 2006 submittal includes all release magnitudes and timing classifications. Only approximately 9% of the total release frequency associated with early containment failure meets the definition of LERF. Potential mitigation from RPV, primary containment, and reactor building filtration, as well as the probability of suppression pool bypass result in a lower fraction of large magnitude releases than the early containment failure mode total release frequency. Additionally, early containment failure is defined as occurring immediately following vessel failure, thus for some plant damage states (PDS) (e.g. Station Black Out with injection until battery depletion or loss of containment heat removal type PDS) the fraction of early containment failure resulting in LERF is reduced due to predicted vessel failure occurring at intermediate times (i.e., between 4 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after General Emergency Declaration).
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© Correspondence Number: NLS2006045 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 4.
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