ML12325A340
| ML12325A340 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 11/20/2012 |
| From: | Bahadur S Division of Policy and Rulemaking |
| To: | Kennedy K NRC/RGN-IV/DRP |
| Cruz H, NRR/DPR, 415-1053 | |
| References | |
| Download: ML12325A340 (8) | |
Text
November 20, 2012 MEMORANDUM TO: Kriss Kennedy, Director Division of Reactor Projects Region IV FROM: Sher Bahadur, Deputy Director /RA by DPelton for/
Division of Policy and Rulemaking Office of Nuclear Reactor Regulation
SUBJECT:
FINAL RESPONSE TO TASK INTERFACE AGREEMENT 2012-08, DIABLO CANYON POWER PLANT, UNIT 1 AND 2 - REQUEST OFFICE OF NUCLEAR REACTOR REGULATIONS REVIEW OF OPERABILITY ISSUES ASSOCIATED WITH TECHNICAL SPECIFICATION 3.7.10, CONTROL ROOM VENTILATION SYSTEM By letter dated July 19, 2012 (Agencywide Documents Access and Management System Accession No. ML12201B295), the U.S. Nuclear Regulatory Commission Region IV Office requested technical assistance from the Office of Nuclear Reactor Regulation (NRR) to determine whether or not the compensatory actions taken by the Diablo Canyon Power Plant (DCPP) licensee to operate the control room ventilation system (CRVS) equipment from both trains was sufficient to satisfy Technical Specification (TS) 3.7.10, Control Room Ventilation System (CRVS), Surveillance Requirement (SR) 3.7.10.5 requirements. The enclosed evaluation documents the NRR staff position regarding DCPP compliance with TS 3.7.10 requirements related to verifying control room envelope (CRE) unfiltered air in-leakage is within limits.
During performance of SR 3.7.10.5, the licensee failed to meet CRVS in-leakage limits which resulted in declaring the CRE inoperable and entering Actions Conditions to restore the CRE to operable status in 90 days. Subsequently, the licensee re-performed SR 3.7.10.5 with a CRVS booster fan from the opposite train in operation. In this configuration CRE in-leakage limits were met and the licensee declared the CRVS operable.
In conducting its review of the licensees operability determination, the NRR staff used the content in DCPP TS 3.7.10, TS 3.7.10 Bases, the guidance in RIS 2005-20, Operability Determinations & Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality or Safety, and docketed correspondence. The NRR staff position is that the compensatory actions taken to operate CRVS equipment from both trains were not sufficient to satisfy TS 3.7.10. The basis for this position can be found in Section 3.0 of the Enclosure.
Enclosure:
As stated CONTACT: Holly D. Cruz, DPR/PLPB (301) 415-1053
- concurred via e-mail with no substantive changes from the draft NRR-106 OFFICE DPR/PLPB/PM DPR/PLPB/LA DSS/STSB/BC DSS/SCVB/BC (A)
NAME HCruz DBaxley* RElliott* HWalker*
DATE 11/20/2012 10/16/2012 10/24/2012 10/17/2012 OFFICE DPR/PLPB/BC (A) DPR/DD NAME SStuchell* DPelton for SBahadur DATE 10/24/2012 11/20/2012 TASK INTERFACE AGREEMENT 2012-08 DIABLO CANYON POWER PLANT, UNITS 1 AND 2 OPERABILITY ISSUES ASSOCIATED WITH TECHNICAL SPECIFICATION 3.7.10 CONTROL ROOM VENTILATION SYSTEM
1.0 INTRODUCTION
By letter dated July 19, 2012 (Agencywide Documents Access and Management System Accession No. ML12201B295), the U.S. Nuclear Regulatory Commission (NRC) Region IV Office requested technical assistance from the Office of Nuclear Reactor Regulation (NRR) to determine whether or not the compensatory actions taken by the Diablo Canyon Power Plants (DCPPs) licensee to operate the control room ventilation system (CRVS) equipment from both trains were sufficient to satisfy Technical Specification (TS) 3.7.10, Control Room Ventilation System (CRVS), and Surveillance Requirement (SR) 3.7.10.5 requirements.
During performance of SR 3.7.10.5, the licensee failed to demonstrate the CRVS was operable by verifying in-leakage limits were met which resulted in declaring the control room envelope (CRE) inoperable and entering Actions Condition B to restore the CRE to operable status in 90 days. Subsequently, the licensee established compensatory measures which entailed maintaining a CRVS booster fan from the opposite train available to restore CRE in-leakage limits; thereby declaring the CRVS to be operable.
In conducting its review of the Pacific Gas and Electric (PG&E) operability determination, the NRR staff used the content in DCPP TS 3.7.10, TS 3.7.10 Bases, and the guidance in Regulatory Information Summary (RIS) 2005-20, Operability Determinations & Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality or Safety, in its review. The NRR staff also used information submitted to NRC in Licensee Event Reports (LERs) 1-201-008-00 and 1-2011-007-01 dated January 3 and January 30, 2012, respectively. The staff also used a License Amendment Request (LAR) dated December 26, 2007, and a letter dated December 2, 2011 (ADAMS Accession No. ML113390057) describing CRE testing.
2.0 BACKGROUND
In January 2005 the CRE was tested to determine the amount of unfiltered air in-leakage. The licensee concluded that the results of the test were adequate to show that the CRE had no unfiltered in-leakage. In a LAR dated December 26, 2007 (ADAMS Accession No. ML080110085), the licensee stated that the 2005 test was the most recent successful test of the CRE.
On September 12, 2011, operators declared the CRE inoperable and entered TS 3.7.10, Condition B, based on inadequate CRE testing performed in 2005. In accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73, PG&E submitted LER 1-2011-007-01 on January 30, 2012 (ADAMS Accession No. ML12031A049).
ENCLOSURE
On November 3, 2011, the licensee identified a CRVS design vulnerability whereby unfiltered air supplied to the control room could exceed the flow rates used in the licensing-basis analysis of design-basis accident (DBA) consequences. The licensee submitted LER 1-2011-008-00 on January 3, 2012 (ADAMS Accession No. ML120040128), in accordance with 10 CFR 50.73 for this issue. The licensee determined that the control room pressurization system airflow could bypass the supply filter if no CRVS booster fan in either train was operating. This would allow as much as 800 standard cubic feet per minute of unfiltered air to be delivered to the control room following an accident that resulted in initiation of the CRVS pressurization mode.
The licensee sought to restore operability of the system by verifying that all components and redundant components in each ventilation train were OPERABLE, and establishing configuration controls to ensure operator dose would continue to meet regulatory limits. The licensee issued a Standing Order instructing operators to enter TS 3.7.10 Condition A any time a CRVS supply fan or a booster fan was not available. Condition A applies when one CRVS train is inoperable for reasons other than an inoperable CRE boundary and requires restoring the inoperable train to operable status within 7 days. The licensee also revised its emergency core cooling system leakage assumptions in its dose calculation model. In November 2011, the licensee performed SR 3.7.10.5, while using these compensatory measures, and obtained acceptable in-leakage flow rates.
TS Task Force (TSTF) Improved Standard Technical Specifications Change Traveler-448, Control Room Habitability, Revision 3 (ADAMS Accession Nos. ML062210095 and ML063630467), includes a discussion of compensatory measures in the bases that accompany this TSTF. TSTF Traveler-448 was issued as part of the consolidated line item improvement program and the licensees request to adopt TSTF-448 was approved on December 23, 2008 (ADAMS Accession No. ML083290609). The licensees TS bases for SR 3.7.10.5, which are essentially identical to those included in TSTF-448 state, in part, that:
The CRE is considered habitable when the radiological dose to CRE occupants calculated in the licensing basis analyses of DBA consequences is no more than 5 rem whole body or its equivalent to any part of the body and the CRE occupants are protected from hazardous chemicals and smoke. For DCPP, there is no CRVS automatic actuation for hazardous chemical releases or smoke and there are no CRVS Surveillance Requirements that verify operability in cases of hazardous chemicals or smoke. This SR verifies that the unfiltered air in-leakage into the CRE is no greater than the flow rate assumed in the licensing basis analyses of DBA consequences. When unfiltered air in-leakage is greater than the assumed flow rate, Condition B must be entered. Required Action B.3 allows time to restore the CRE boundary to OPERABLE status provided mitigating actions can ensure that the CRE remains within the licensing basis habitability limits for the occupants following an accident.
Compensatory measures are discussed in Regulatory Guide [(RGs)] 1.196, (Ref. 8) Section C.2.7.3, which endorses, with exceptions, NEI [Nuclear Energy Institute] 99-03 (Ref. 9), Rev. 0, Section 8.4 and Appendix F. These compensatory measures may also be used as mitigating actions as required by Required Action B.2. Temporary analytical methods may also be used as compensatory measures to restore OPERABILITY (Ref. 10). Options for restoring the CRE boundary to OPERABLE status include changing the licensing
basis DBA consequence analysis, repairing the CRE boundary, or a combination of these actions. Depending upon the nature of the problem and the corrective action, a full scope inleakage test may not be necessary to establish that the CRE boundary has been restored to OPERABLE status.
Regulatory Guide 1.196, Control Room Habitability at Light-Water Nuclear Power Reactors, May 2003 (ADAMS Accession No. ML031490611), and NEI 99-03, Control Room Habitability Assessment Guidance, June 2001 (ADAMS Accession No. ML020600236), are referenced in the TS Bases. RG 1.196 states that methods to address short-term degraded or nonconforming conditions are provided in Section 8.4, Methods Available to Address Degraded or Nonconforming Conditions, of NEI 99-03, consistent with the above discussion in the TS Bases. In addition, the TS Bases, also reference a letter from Mr. Eric Leeds dated January 30, 2004, NEI Draft White Paper, Use of Generic Letter 91-18 Process and Alternative Source Terms in the Context of Control Room Habitability (ADAMS Accession No. ML040300694).
Licensees Position:
The licensee position is that the CRE is operable due to compensatory actions implemented in the operability determination. The operability determination was approved in 2011 to address the design deficiency and implemented compensatory actions to restore CRVS/CRE operability.
The compensatory actions prohibit operation as permitted by the TS 3.7.10 Condition A (securing one CRVS train) because the design deficiency results in the TS inadequately controlling plant configuration to maintain operator dose less than 5 rem whole body dose equivalent. The compensatory actions ensure that the CRVS will maintain operator dose from exceeding 5 rem whole body while continuing to meet single failure design requirements.
The licensee stated that the individual CRVS trains are operable based on the same compensatory actions. The DCPP Final Safety Analysis Report (FSAR) and TS basis specify that the system is designed to meet the single failure design requirements. The FSAR and the TS describe different methods by which the system meets the single failure criteria. The method of satisfying the single failure criteria described in the TS 3.7.10 basis is not met with the existence of the design deficiency. However the compensatory actions established ensure that the FSAR-described single failure methodology remains assured, and CRVS compliance with the single failure design requirements is maintained.
The licensee believes that RG 1.196 allows the use of compensatory measures to restore operability of the CRVS. The licensees interpretation is based on several sentences in the TS 3.7.10.4 Bases of TSTF - 448 for including:
Required Action B.3 allows time to restore the CRE boundary to OPERABLE status provided mitigating actions can ensure that the CRE remains within the licensing basis habitability limits for the occupants following an accident.
The licensee believes that the two compensatory actions it has taken (i.e., running a booster fan and making changes to the assumptions in its dose model) are consistent with those actions described in Section 8.4 of NEI 99-03, which is endorsed by the NRC staff. Furthermore, the licensee believes that by taking these actions, the CRVS at DCPP is OPERABLE.
In addition, the licensee references the following from the TSTF Traveler 448 TS 3.7.10.4 Bases:
Temporary analytical methods may also be used as compensatory measures to restore OPERABILITY (Ref. 7). Options for restoring the CRE boundary to OPERABLE status include changing the licensing basis DBA consequence analysis, repairing the CRE boundary, or a combination of these actions.
The licensee, therefore, believes that compensatory measures to restore operability to the CRVS can go beyond analytical methods and can include a modification to the facility other than restoration to the original FSAR condition in accordance with the January 30, 2004, letter from Eric Leeds, which is referenced in TSTF Traveler 448.
3.0 EVALUATION On September 12, 2011, operators declared the CRE inoperable and entered TS 3.7.10, Actions Condition B, based on inadequate CRE testing performed in 2005. Region IV requested NRR staff review of the licensees compliance with TS 3.7.10 to determine if the compensatory action taken to operate CRVS equipment from both trains was sufficient to satisfy TS 3.7.10 and SR 3.7.10.5.
TS 3.7.10 Actions Condition B Required Action B.1 requires immediate initiation of actions to implement mitigating actions to lessen the effect on CRE occupants from the potential hazards of a radiological or chemical event or a challenge from smoke. Required Action B.2 requires verification within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> that, in the event of a DBA, the mitigating actions will ensure that CRE occupant radiological exposures will not exceed the calculated dose of the licensing basis analyses of DBA consequences, and that CRE occupants are protected from potential smoke and chemical hazards. Required Action B.3 requires restoring the CRE to operable status within 90 days. The 90 day Completion Time is based on the determination that the mitigating actions of Required Actions B.1 and B.2 will ensure protection of the CRE occupants within analyzed limits while limiting the probability that CRE occupants will have to implement protective measures that may adversely affect their ability to control the reactor and maintain it in a safe shutdown condition in the event of a DBA. That is, continued operation while in Condition B for 90 days is not allowed unless Required Actions B.1 and B.2 are completed within their respective completion times. 90 days is also a reasonable time to diagnose, plan and possibly repair and test most problems with the CRE boundary.
The Bases of SR 3.7.10.5 contains an expanded discussion of situations when the CRE is inoperable, Required Actions B.2 and B.3, as well as the requirements related to the test to assure that the CRE can perform its safety function. The SR 3.7.10.5 Bases outline acceptable compensatory measures for situations when the CRE is inoperable. The particular discussion is contained in Section 2.0 of this Enclosure, in the excerpt from the licensees TS Bases. The NRR staff believes that some of the Bases language can be misconstrued due to poor formatting choices. However, the Bases discussion of compensatory measures and mitigating actions pertains to acceptable ways in which Required Action B.2 could be completed.
Therefore, the Bases language: Options for restoring the CRE boundary to OPERABLE status include changing the licensing basis DBA consequence analysis, repairing the CRE boundary, or a combination of these actions establishes an acceptable basis for which compensatory measures may be used in lieu of complying with Required Action B.3.
The NRR staff believes the compensatory actions taken by the licensee were sufficient to comply with TS 3.7.10 Required Actions B.1 and B.2 and the licensee completed Required Actions B.1 and B.2 within the respective Completion Times. However, the NRR staff believes the compensatory actions to operate CRVS equipment from both trains are not sufficient to restore the CRE to OPERABLE status as required by Required Action B.3 because the licensee has not changed the licensing basis DBA or repaired the CRE boundary or performed a combination of these actions. The licensee has implemented compensatory measures that are appropriate to complete Required Actions B.1 and B.2, but not appropriate to complete Required Action B.3. The compensatory action taken to operate CRVS equipment from both trains was not sufficient to satisfy TS 3.7.10 requirements because B.3 was not completed.
Further, SR 3.7.10.5 requires testing the CRE in-leakage with the CRVS in the design basis accident configuration to verify the OPERABILITY of the CRE boundary. Operation of CRVS equipment from both trains is not credited in the CLB as part of the design basis configuration.
Performing the in-leakage test with CRVS equipment from the opposite train in operation does not satisfy the requirements for performing SR 3.7.10.5. Therefore, testing in such a configuration means the SR has not actually been performed, regardless of the in-leakage flow rates obtained, and the CRE has not been restored to OPERABLE status. Since SR 3.0.1 states that failure to meet a SR shall be failure to meet the LCO, TS 3.7.10 requirements have not been met.
The NRR staff position is that the compensatory action taken to operate CRVS equipment from both trains was not sufficient to satisfy TS 3.7.10 and SR 3.7.10.5 requirements. SR 3.7.10.5 has not been performed in a manner that would reestablish the operability of the CRE. The compensatory measures the licensee would like to rely on to restore CRE operability are inappropriate for the inoperable CRE.
The Completion Time of 90 days for Required Action B.3 is the longest Completion Time in TS.
This time was allowed because of the expected amount of time required to diagnose, plan, repair, and retest most conditions that could render the CRE inoperable. The NRR staff believes the licensee should be able to begin final corrective actions within 90 days. If the final corrective actions cannot be completed within the 90 days, a licensing action may be required if the licensee desires to continue operation in the Modes of applicability for the LCO.
4.0 REGULATORY REQUIREMENTS Section 182a of the Atomic Energy Act (the Act) requires applicants for nuclear power plant operating licenses to include TS as part of the license. The TS ensure the operational capability of structures, systems and components that are required to protect the health and safety of the public. The regulatory requirements related to the content of the TS are contained in 10 CFR 50.36. That regulation requires that the TS include items in the following specific categories: (1) safety limits, limiting safety systems settings, and limiting control settings (50.36(c)(1)); (2) limiting conditions for operation (50.36(c)(2)); (3) SRs (50.36(c)(3)); (4) design features (50.36(c)(4)); and (5) administrative controls (50.36(c)(5)).
10 CFR 50.36(c)(2) states, in part:
Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition
for operation of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.
10 CFR 50.36(c)(3) states, in part:
Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.
Appendix A of the DCPP, Units 1 and 2, Operating Licenses contain the TS for the Units.
Page 3.0-1 contains LCO 3.0.2, which states:
Upon discovery of a failure to meet an LCO, the Required Actions of the associated Conditions shall be met, except as provided in LCO 3.0.5 and LCO 3.0.6.
If the LCO is met or is no longer applicable prior to expiration of the specified Completion Time(s), completion of the Required Action(s) is not required unless otherwise stated.
Page 3.0-3 of the TS contains SR 3.0.1, which states:
SRs shall be met during the MODES or other specified conditions in the Applicability for individual LCOs, unless otherwise stated in the SR. Failure to meet a Surveillance, whether such failure is experienced during the performance of the Surveillance or between performances of the Surveillance, shall be failure to meet the LCO. Failure to perform a Surveillance within the specified Frequency shall be failure to meet the LCO except as provided in SR 3.0.3. Surveillances do not have to be performed on inoperable equipment or variables outside specified limits.
5.0 CONCLUSION
The licensee has not changed the licensing basis DBA or repaired the CRE boundary or performed a combination of these actions. The licensee has implemented compensatory measures that are acceptable to complete Required Action B.2, but not acceptable to complete Required Action B.3. Performing the in-leakage test with CRVS equipment from both trains in operation does not satisfy the requirements for performing SR 3.7.10.5. The compensatory action taken to operate CRVS equipment from both trains was not sufficient to satisfy TS 3.7.10.
Principal Contributor: Matthew Hamm Date: November 20, 2012