NOC-AE-08002291, Clarification of the Applicability of Risk Managed Technical Specifications to Technical Specification 3.7.7

Clarification of the Applicability of Risk Managed Technical Specifications to Technical Specification 3.7.7

ML081720133
Person / Time
Site:	South Texas
Issue date:	05/28/2008
From:	Head S South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-08002291, STI: 32298143
Download: ML081720133 (4)

Text

Nuclear Operating Company South TewasPromect Electric Generatn Station, PO. Box 289 Wadsworth. Tebas 77483 -

May 28, 2008 NOC-AE-08002291 10CFR50.36 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Clarification of the Applicability of Risk Managed Technical Specifications to Technical Specification 3.7.7

References:

1. Letter dated Decembler 28, 2006, from David W. Rencurrel, STPNOC, to NRC Document Control Desk, "Revised Broad Scope Risk-Informed Technical Specification Amendment Request" (ML070040247, NOC-AE-06002036, TAC Nos. MD2341 & MD2342)

2. Letter dated July 13, 2007, from Mohan C. Thadani, NRC, to James J. Sheppard, STPNOC, "South Texas Project, Units I and 2 - Issuance of Amendments Re: Broad-Scope Risk-Informed Technical Specifications Amendments (TAC Nos. MD234i and MD2342)" (ML071780186, ML071780191)

In Reference 1, the STP Nuclear Operating Company (STPNOC) submitted a revised license amendment request for a broad scope risk-informed set of Technical Specification (TS) changes. The proposed amendment was approved in Reference 2 with the issuance of Amendment 179 and Amendment 166 to the STP Unit I and Unit 2 operating licenses, respectively. STPNOC is submitting this letter to correct a statement in Reference 1 with respect to the application of Risk Managed Technical Specification (RMTS) to Technical Specification (TS) 3.7.7, "Control Room Makeup and Cleanup Filtration System" and to clarify how RMTS is to apply to TS 3.7.7. The incorrect statement resulted in the potential for a noncompliance with the basis for the license amendment, but had no potential to significantly affect safety.

Background and

Description:

On July 13, 2007, Amendments 179 and 166 to the TS approved the RMTS to allow the Configuration Risk Management Program (CRMP) to be applied to various STP TS for extending ACTION times for inoperable trains. The amendment permitted the CRMP to be applied to TS 3.7.7 on a limited basis.

The Control Room Makeup and Cleanup Filtration System (CRMCFS), commonly referred to as Control Room HVAC (CRHVAC), includes a recirculation and filtration function that maintains the design basis accident radiation dose to the operators within the limits of General Design Criteria 19. The system also provides required cooling for the operators and equipment. The dose mitigation function is not modeled in the STP Probabilistic Risk Assessment (PRA) because it is evaluated as having no impact on core STI: 32298143

NOC-AE-08002291 Page 2 damage frequency (CDF) or large early release frequency (LERF), which are the metrics for application of RMTS. The cooling function is modeled. Based on discussion with the NRC reviewers, it was determined during the license amendment application review that the dose mitigation function could not be included in the scope of RMTS because it is not modeled in the PRA.

At the time the amendment was approved, STPNOC believed the dose mitigation function was independent of the cooling function and the CRMP could be applied to TS 3.7.7 for conditions where only the cooling function is affected. The "limited" basis approved in the license amendment allows the CRMP to apply to conditions where only the cooling function of the CRHVAC is affected. Reference I addressed this by stating that the wording below would be included in the TS Bases for TS 3.7.7, and the TS Bases were changed accordingly.

"The dose mitigation function governed by TS 3.7.7 does not depend on the cooling function governed by TS 3.7.7 that is supported by TS 3.7.14 for EchW. Therefore, if a TS 3.7.7 action applies because EchW is not available or the cooling coil for CRHVAC is not operable, the provision to apply the CRMP may be used."

During a review of the basis for application of RMTS in February 2008, STPNOC determined that at least one train of Essential Chilled Water (EchW) supported by Essential Cooling Water (EW) is required to maintain humidity to support achieving the filter efficiency assumed in the accident dose analysis. Based on this information, the dose mitigation function governed by TS 3.7.7 has some dependence on the cooling function and the statement above is not correct.

The discrepancy in the information was entered in the STPNOC Corrective Action Program and administrative restrictions were put in place to prevent the use of RMTS for CRHVAC. STPNOC has not applied RMTS to TS 3.7.7. The discrepancy had the potential to result in a noncompliance with the' licensing basis for the approval of the amendment; however, because of the low risk significance of the dose mitigation function, it had no potential to significantly affect safety.

Clarification of Applicability of RMTS to TS 3.7.7:

STP TS 3.7.7 requires the operability of three independent trains of CRHVAC. The required actions of TS 3.7.7 are shown below.

a. With one Control Room Makeup and Cleanup Filtration System inoperable, within 7 days restore the inoperable system to OPERABLE status or apply the requirements of the CRMP, or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

b. With two Control Room Makeup and Cleanup Filtration Systems inoperable, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> restore at least two systems to OPERABLE status or apply the requirements of the CRMP, or be at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

c. With three Control Room Makeup and Cleanup Filtration Systems inoperable, suspend all operations involving movement of spent fuel, and crane operation with loads over the spent fuel pool, and within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> restore at least one system to OPERABLE status or apply the requirements of the CRMP, or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

NOC-AE-08002291 Page 3 In response to the discrepancy described above, STPNOC performed a calculation that determined that two trains of CRHVAC pressurization (fans) with one train of cooling is adequate for the dose mitigation function based on maintaining the required control room envelope positive pressure and maintaining the relative humidity of the control room air below the 70% acceptance criteria required to support design basis assumptions for carbon filter efficiency. The calculation shows that with a train of CRHVAC in TS 3.7.7 Action a for loss of cooling (i.e., the associated train of EW or EChW is inoperable), either of the two operable trains of CRHVAC provides adequate cooling to maintain the filter efficiency for the CRHVAC system to perform its design function to mitigate dose. STPNOC concluded that the system is capable of meeting its dose mitigation function in this configuration. Therefore, application of the CRMP to TS 3.7.7 Action a for one train of CRHVAC inoperable because it cannot perform its cooling function is permissible in accordance with the Bases for the TS.

For TS 3.7.7 Action b or Action c, application of the CRMP would be to extend the time to restore the required redundancy for the unmodeled dose mitigation function and is not allowed.

STPNOC has revised the Bases for TS 3.7.7 to allow application of the CRMP only to TS 3.7.7 Action a.

Follow-up Actions:

STPNOC plans to submit a license amendment request to permit unrestricted application of RMTS to TS 3.7.7 by October 2, 2008.

There are no commitments in this letter.

If you have any questions, please call Wayne Harrison at 361-972-7298 or me at 361-972-7136.

Scott M. Head Manager, Licensing

NOC-AE-08002291 Page 4 cc:

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Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 612 East Lamar Blvd, Suite 400 Arlington, Texas 76011-4125 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Thad Hill Senior Project Manager Catherine Callaway U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 7 D1) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Ed Alarcon Senior Resident Inspector J. J. Nesrsta U. S. Nuclear Regulatory Commission R. K. Temple P. 0. Box 289, Mail Code: MN1 16 Kevin Pollo Wadsworth, TX 77483 City Public Service C. M. Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department.

721 Barton Springs Road C. Kirksey Austin, TX 78704 City of Austin Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189