ML13330B317
| ML13330B317 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/31/1988 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-88-05, GL-88-5, TAC-68946, NUDOCS 8806030365 | |
| Download: ML13330B317 (4) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M.O:MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING May 31 198 191> 302-1749 AND LICENSING U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Response to NRC Generic Letter 88-05 Docket Nos. 50-206, 50-361 and 50-362 San Onofre Nuclear Generating Station Units 1, 2 and 3 NRC Generic Letter 88-05, dated March 17, 1988 requested licensees to affirm that programs were being established to address boric acid corrosion of carbon steel reactor coolant pressure boundary (RCPB) components resulting from leakage below technical specifications limits.
Independent of this request, in July 1987, the Southern California Edison Company established a boric acid leakage reduction task force. Consequently, many programmatic elements are already in place which address the issues identified by Generic Letter 88-05.
SCE believes that these elements in conjunction with other task force recommendations which are to be implemented constitute an acceptable program with respect to the Generic Letter requirements. Although the Generic Letter did not request submittal of the program, SCE considers that a brief description of the most significant aspects relative to the Generic Letter requirements is necessary to establish a common understanding of our program's scope. The enclosure addresses each of the four items identified in Generic Letter 88-05.
As identified in the enclosure, SCE relies heavily on existing practices to address boric acid leakage. By July 1, 1988 a revision will be made to the Nonconformance Report (NCR) program to address boric acid leakage. This revision will ensure that any boric acid leakage discovered will be documented and dispositioned using the NCR program. Additionally, by September 1988, the Station Technical organization will implement a procedure which will formalize and integrate practices related to boric acid leakage control.
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Document Control Desk May 31, 1988 SCE is confident that these provisions will satisfy the requirements of Generic Letter 88-05. Should you have any questions regarding the information provided by this letter, please call me.
Respectfully submitted, M. 0. Medford Manager of Nuclear Engineering and Licensing Subscribed and sworn before me this JAd day of 1988.
AGNES CRABTREE Notary Public-California A.1 LOS ANGELES COUNTY Noty Public in and for the County MyComm.Exp.Sep.149 of os Angeles, State of California Enclosure cc: 3. B. Martin Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3
ENCLOSURE RESPONSE TO GENERIC LETTER 88-05 (1) A determination of the principal locations where leaks that are smaller than the allowable technical specification limit can cause degradation of the primary pressure boundary by boric acid corrosion. Particular consideration should be given to identifying those locations where conditions exist that could cause high concentrations of boric acid on pressure boundary surfaces.
It has been the practice at San Onofre to conduct visual inspections for RCPB leakage as part of Operations walkdowns of the RCPB at normal operating temperature and pressure (Mode 3).
These walkdowns are routinely conducted at outages which permit access to containment for sufficient duration including refueling outages, as a minimum.
Experienced maintenance and engineering personnel are included on the team performing the walkdown. The use of an experienced team ensures a thorough visual inspection of the containment. Principal locations where leaks could occur have been identified through experience gained in past walkdowns. The responsible participating Station Technical engineer ensures that the principal locations are examined.
These visual inspections have proven to be effective in identifying boric acid leakage. Procedure revisions will be written to formalize the existing inspection points. Procedures will identify specific areas to be visually inspected, and where necessary, provide detailed guidance regarding obscure locations within an area. Procedure revisions will be in place by September 1988, in time for the next refueling outage for each unit.
(2) Procedures for locating small coolant leaks (i.e., leakage rates at less than technical specification limits). It is important to establish the potential path of the leaking coolant and the reactor pressure boundary components it is likely to contact. This information is important in determining the interaction between the leaking coolant and reactor coolant pressure boundary materials.
Reactor Coolant System (RCS) inventory balances conducted at frequencies specified in technical specifications and containment airborne radiation monitors are the principal means used for leakage detection. The RCS inventory balance sensitivity is approximately 0.1 gpm at Unit 1 and approximately 0.035 gpm at Units 2 and 3. Radiation monitor sensitivity is approximately 0.01 gpm, but is a function of RCS activity.
Unidentified leakage data is routinely trended. Although there is no specific action threshold below the 1 gpm unidentified leakage T.S.
criteria, significant changes in measured leakage are investigated.
Appropriate methods are used to identify the location of the leak such as analysis of pressurizer steam space samples. In the past, it has been possible to determine the general location of leaks during power operation. Leaks determined to be outside the bio-shield can be examined during power operation. An assessment is made of all leaks discovered during operation to determine the appropriate course of action, including shutdown of the unit, if necessary.
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-2 (3) Methods for conducting examinations and performing engineering evaluations to establish the impact on the reactor coolant pressure boundary when leakage is located. This should include procedures to promptly gather the necessary information for an engineering evaluation before the removal of evidence of leakage, such as boric acid crystal buildup.
Evidence of leakage is most often discovered during Operations walkdowns at the beginning of an outage. Currently, the responsible Station Technical engineer participating in the walkdown assesses identified leaks and prescribes appropriate corrective action. For example, in a case of apparent leakage from a valve packing where boric acid residue was localized, not affecting carbon steel or other components, a maintenance order would be initiated which would allow cleanup of any boric acid residue and adjustment of the valve packing. In a more severe case where boric acid crystals are caked on adjacent components or where past corrective action, such as packing adjustment, was not effective in preventing recurrence of the leakage, a Nonconformance Report (NCR) would be initiated. Evidence of boric acid leakage is rarely discovered at times other than during walkdowns. Specific action taken in these cases depends on the circumstances, but generally results in a maintenance order or NCR.
Revisions to Station Technical procedures and to the NCR procedure will result in all identified boric acid leaks being subject to the NCR program. The NCR procedure provides for thorough investigation of identified deficiencies, evaluation of their effects and identification of corrective actions.
This change will add more formality and an engineering review to the existing process and ensure appropriate priority in the evaluation and elimination of boric acid leaks.
By July 1, 1988 program revisions will ensure that any boric acid leakage discovered will be evaluated and dispositioned using NCR's.
(4) Corrective actions to prevent recurrences of this type of corrosion.
This should include any modifications to be introduced in the present design or operating procedures of the plant that (a) reduce the probability of primary coolant leaks at the locations where they may cause corrosion damage and (b) entail the use of suitable corrosion resistant materials or the application of protective coatings/claddings.
Use of the existing NCR program will require that all boric acid leakage be adequately evaluated which may include a formal "Root Cause Evaluation," and that the identified corrective actions be implemented which could include design changes to minimize sources of leakage and the use of corrosion resistant materials, as necessary.
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