ML20154B884

Safety Evaluation Accepting Response to Generic Ltr 88-05, Boric Acid Corrosion of Carbon Steel Reactor Pressure Boundary Components in PWR Plants

ML20154B884
Person / Time
Site:	Dresden, Sequoyah, NS Savannah
Issue date:	09/09/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
Shared Package
ML20154B867	List: ML20154B862 ML20154B884
References
GL-88-05, GL-88-5, NUDOCS 8809140172
Download: ML20154B884 (2)

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'o, UNITED STATES 5' e NUCLE AR REGULATORY COMMISSION

{. :I WASHINGTON, D. C. 20666 ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS RESPONSE TO GENERIC LETTER 88-05 BORIC ACID CORROSION OF CARBON STEEL REACTOR PRES $URE BOUNDARY COMPONENTS IN PWP PLANTS TENNESSEE VALLEY AUTHORITY SE000YAH NUCLEAR PLANT, UNITS 1, AND 2 DOCKET NOS. 50-237. AND 50-238

1.0 INTRODUCTION

Ry Generic letter O-05 dated March 17, 1988, NRC requested information from pressurized water reactor (PWR) licensees to assess safe operation of their I plants when reactor ecolant leaks below Techrical Specification (TS) limits I develop and the coolant containing dissolved boric acid comes in contact with and degrades low carbon steel components. The principal concern is the corrosion of the carbon steel reactor coolant pressure boundary (RCPB) to the extent that General Design Criteria (GDC) 14, 30 and 31 of Appendix A to 10 CFR Part 50 may not be net. Several occurrences at operating plants resulted in significent corrosion of RCPB components. In many cases, although t the licensees had detected leaks, they had not evaluated their significance relative to the safety of the plant nor had they promptly taken appropriate corrective actions.

The Generic Letter requested PWR licensees to develop and implement a program to ensure that boric acid corrosion of carbon steel RCPB components will not degrade the boundary such that its integrity is threatened. Program guidelines required four elements: (1) a determination of the principal locations where leaks smaller than allowable TS limits can cause degradation of the primary RCPB by boric acid corrosion, (2) procedures for locating small coolant leaks less than TS limits. (3) methods of conducting examinations and perfonning engineering evaluations to establish the impact on the RCPB when leakage is detected, and (4) corrective actions to prevent recurrences of this type of corrosion.

2.0 EV ALUATION The Tennessee Valley Authority's (TVA's) initial response of June 1, 1988, related to operating pressure and temperature tests for startup of Sequoyah Nuclear Plant, Unit 2, where visual inspections of the RCPB for leakage, evidence of leakage, and corrosion were made. A supplenental response dated July 29, 1988, describe.t TVA's nian to develop an Engineering Requirements l Specification and subsequent auions to be taken to establish its program.

Three of the four key considerations were directly addressed in the July 29,

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1988 letter; however, the procedures for locating small coolant leaks less than TS limits were not directly addressed. TVA has comnitted to implement this ,

l program at the Sequoyah site by March 1,1989. .

In its letter dated July 29, 1998 TVA comnitted to (1) issue the Engineering l Requirements Specification for boric acid corrosion centrol by September 30, 1688, and (2) implement the Sequoyah program for boric acid corrosion to ,

comply with the requirements in GL 88-05 through existing plant procedure i

revisions and development of a new plant procedure, as applicable, by March 1, 1989. This is acceptable.

3.0 CONCLUSION

Based on the staff review of the submittals for the Sequoyah site, the staff concludes that the TVA response to GL 88-05 is acceptable. Although methnds for locating small coolant leaks less than TS limits were not directly addressed, the elements of the means of locating small coolant leaks (monitoring and surveillance) and the use of industry experience end recommendations from industry working groups on boric acid corrosion are mentioned. Accordingly. TVA is viewed as being cognizant of what is necessary to establish an acceptable program. The Sequoyah site should be in:luded in the population of plants to be audited by NRC in the future in accordance with the generic letter.

4.0 REFERENCES

1. Generic Letter 88-05, Boric Acid Corrosion of Carbon Steel Peactor Pressure Boundary Components in PWR Plants, dated March 17, 1988,

2. Letter from TVA dated June 1, 1988.

3. Letter fron TVA dated July 29, 1988.

Principal Contributor: D. E. Smith >

Dated: September 9,1988 1

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