ML101870434
| ML101870434 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/02/2010 |
| From: | Plant Licensing Branch 1 |
| To: | |
| Hughey J, NRR/DORL, 301-415-3204 | |
| Shared Package | |
| ml101870425 | List: |
| References | |
| Download: ML101870434 (2) | |
Text
Enclosure DRAFT REQUEST FOR INFORMATION RELATED TO ACCEPTANCE REVIEW REGARDING LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 3.1.7 STANDBY LIQUID CONTROL SYSTEM COMPLETION TIME FOR CONDITION C PEACH BOTTOM ATOMIC POWER STATION - UNITS 2 AND 3 DOCKET NOS. 50-277 AND 50-278 By letter to the Nuclear Regulatory Commission (NRC) dated March 24, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML100840752), Exelon Generation Company, LLC, (Exelon) submitted a request to revise the technical specifications (TS) for the Peach Bottom Atomic Power Station, (PBAPS) Units 2 and 3. The proposed change would revise TS Section 3.1.7, Standby Liquid Control (SLC) System, to extend the completion time for condition C (i.e., Two SLC subsystems inoperable for reasons other than Condition A) from 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Supplemental Request - 01:
The NRC staff requests that Exelon clarify the intended reliance on EOP actions as an alternate means of boration and provide evaluations that justify any credited actions related to the requirements of 10 CFR 50.67, as appropriate.
Page 6 of Attachment 1 to the license amendment request (LAR) describes alternative means for boration as additional redundancy in support of defense-in-depth measures to justify the proposed extension of the TS 3.1.7, condition C, completion time. These alternative means of boration consist of actions in the PBAPS Emergency Operating Procedures (EOP). Page 3 of of the LAR states that the alternative means of boration support the stations ability to meet the requirements of Title 10 Code of Federal Regulations Part 50, Section 50.67 (10 CFR 50.67), Accident source term.
The NRC staff has identified that the proposed alternate means of boration are not currently included in the PBAPS licensing basis. The LAR indicates that the licensee intends to credit the referenced EOP actions as an alternate boration pathway to meet the requirements of 10 CFR 50.67. If so, then additional justification is required to support reliance on these actions as a credited alternate boration pathway. The NRC document Guidance on the Assessment of a BWR [boiling-water reactor] SLC System for pH Control, dated February 12, 2004 (ADAMS Accession No. ML040640364), provides an approach that is acceptable to the NRC staff for evaluating the alternative controls of the suppression pool pH against appropriate methodologies. If Exelons intent is not to credit a new alternate boration pathway, then clarification is needed regarding the use of the EOP actions as an alternative means of boration with respect to defense-in-depth as related to 10 CFR 50.67.
Supplemental Request - 02:
Identify adequate defense-in-depth for mitigation of ATWS events for the extended 72-hour completion time period.
The SLC System mitigates an (anticipated transient without scram) ATWS event by delivering a concentrated borated solution to the reactor pressure vessel to shutdown the reactor. The TS Required Action being modified addresses the condition where both SLC trains are inoperable.
In the event of an ATWS during this condition, there is no system available to inject concentrated borated solution into the reactor pressure vessel in a timely manner to achieve shutdown. The licensee submittal addresses the low probability of an ATWS event due to the reliability and diversity of the control rods, and also discusses the recirculation pump trip feature which reduces reactor power. However, there is no mechanism identified to assure safe shutdown to subcritical conditions as normally ensured by the operation of one of the two SLC trains.