ML20246D681

Safety Evaluation Supporting Installation & Design of Nitrogen Pneumatic Sys,Per Generic Ltr 84-09,by Adding New Check Valves to Existing Drywell Noninterruptible Instrument Air Lines

ML20246D681
Person / Time
Site:	Brunswick
Issue date:	08/18/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20246D669	List: ML20246D666 ML20246D681
References
GL-84-09, GL-84-9, NUDOCS 8908280223
Download: ML20246D681 (3)

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l SAFETY EVALUATION BY-THE OFFICE OF NUCLEAR RACTOR REGULATION RELATING TO THE DESIGN AND INSTALLATION OF THE NITROGEN PNEUMATIC SYSTEM CAROLINA POWER & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 DOCKET NOS. 50-325 AND 50-324

1.0 INTRODUCTION

In response to Generic Letter (GL) 84-09, "Recombiner Capability Require-ments of 10 CFR 50.44(c)(3)(ii)," Carolina Power & Light Company (CP&L) made several submittals (datea June 8, 1984, June 27, 1984, March 4, 1985, July 18, 1985, and March 20, 1986, December 12, 1986, March 27, 1987, November 20, 1987, March 10, 1986 and November that Brunswick Steam Electric Plant, Units 1 and 15,1988)},todemonstrate 2 (BSEP does not require hydrogen recombiners to control combustible gases after an accident. CP&L proposes to install a safoty-grade quality nitrogen backup system for use in conjunction with the nitrogen pneumatic air system, as a method for compliarce with GL 84-09. Details of CP&L's proposed installation and results of the NDC staff review are as follows:

A system description, related design information, and an amendment request to incorporate system operability and surveillance requirements into the BSEP Technical Specifications for the backup system were provided to the staff by the December 19, 1986 anc harch 27, 1987 submittals. CP&L has stated in these submittals that the nitrogen backup system is oesigned.as i a seismic, environmentally qualifiea Q-list system consisting of two i redundant divisions. The nitrogen backup system will automatically supply 3 pressurized nitrogen gas to the safety-related instrument system upon receipt of containment isolation or LOCA signals. Along with these submittals, CP&L also committed to install an additional isolation valve on the existing instrument air lines inside the drywell. The staff reviewed the submitted material and found the design and installation of the backup system to be acceptable. The staff also approved the new backup system and the related CP&L requested amendment on August 20, 1987.

By letter dated November 20, 1987, CP&L requested staff approval to replace the normal noninterruptible instrument air supply with a full-time pressurized nitrogen system to supply controlled nitrogen pressure to instruments inside containment, instead of installing additional isolation valves on the existing instrument air lines as committed to in the previous submittals. In the same November 20, 1987 letter, CP&L requested staff approval to delay the installation schedule of the new full time nitrogen system for Unit 2.

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l r-On December 17, 1987, the NRC staff approved CP&L's request to ' delay the

. installation of the full-time nitrogen system on Unit 2 until the Cycle 8 reload outage which is scheduled to begin on September 9, 1989. With this approval, the staff also requested that CP&L provide the staff with informa-tion related to the design of the nitrogen pneumatic system prior to the start of the Unit 1 Cycle 6 reload outage. f i

By letter dated March 10, 1988, CP&L submitted the design related informa- ]

tion for the nitrogen pneumatic system, which included system description, piping and instrumentation diagram, general system arrangement, and the piping routing plan for inside of the reactor building. The staff performed a preliminary review of the submitted information and found that the design did not meet the requirements of 10 CFR Part 50, Appendix A, Design Criterion 56, for primary containment penetration isolation for the new system. A meeting between the NRC staff and CP&L was held on April 9, .1988 to resolve the staff concern. At this meeting, CP&L committed to re-examine the design j of the nitrogen pneumatic system and related requirements for system contain- j ment penetration isolation.

By letter dated November 15, 1988, CP&L informed the staff that the nitrogen pneumatic system design had been re-evaluated and CP&L is committed to add a new check valve to the existing noninterruptible instrument air lines inside the drywell. Because the new full time nitrogen system.is designed to share a penetration and a portion of the piping with existing instrument air lines, the installation of the new check valve is needed to satisfy 10 CFR Part 50, Appendix A, Design Criterion 56 (for coraainment isolation requirement) for the new full time nitrogen system. CP&L further stated that the system will eliminate the introduction of oxygen into the drywell during plant operation and that the nitrogen system may be isolated during a plant outage and the existing noninterruptible instrument air system may te used while plant personnel are working and entering the drywell. In th u same Novenber 15, 1988 letter, TP&L also-provided design details and a system description for the nitrogen pneumatic system, and valve details and the basis for the new check valve. In the basis for installation of the new check valve, CP&L describes how the new valve will function as a second i isolation device and act as a barrier between the containment and the l outside atmosphere in the case of an accident that is coincident with a j breach of the drywell's noninterruptible instrument air lines.

2.0 EVALUATION The staff has reviewed the above submitted design information, system description, and piping drawings on the nitrogen pneumatic system, as well as information on the new check valve. Following are results of the '

staff review:

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(1) The nitrogen pneumatic syst.tm is designed to Class I seismic requirements with the capability of' supplying all the nitrogen required in the drywell for plant safety. The nitrogen backup system provides an independent pneumatic source of bottled nitrogen to selected safety-related loads in the. drywell in the event of either a LOCA or the loss of the nitrogen pneumatic system. Should the nitrogen backup system become inoperable, the control room operator can override the isolation of the nitrogen pneumatic system by using a control switch in the control room. Therefore, the nitrogen pneumatic system is also designed to operate during any design basis event.

(2) CP&L's analysis and basis for adding the new check valves on the existing drywell noninterruptible instrument air lines are adequate and meet the containment isolation requirements specified in 10 CFR Part 50, Appendix A, Criterion 56.

In conclusion, the staff finds that the design and installation of the new nitrogen pneumatic system and the adding of the new check valves to the existing drywell noninterruptible instrument air lines at BSEP are acceptable for compliance with the provisions of GL 84-09. $

Princip&l Contributor: N. B. Le Dated: August 18, 1989

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