ML20244D758
| ML20244D758 | |
| Person / Time | |
|---|---|
| Issue date: | 03/24/1986 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| Shared Package | |
| ML20244D762 | List: |
| References | |
| REF-GTECI-A-03, REF-GTECI-A-04, REF-GTECI-A-05, REF-GTECI-SG, TASK-A-03, TASK-A-04, TASK-A-05, TASK-A-3, TASK-A-4, TASK-A-5, TASK-OR GL-85-02, GL-85-2, NUDOCS 8604030305 | |
| Download: ML20244D758 (8) | |
Text
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.. j March 24, 1985 SECY-86-97 FOR: The Commissioners FROM: Victor Stello, Jr.
Acting Executive Director for Operations
SUBJECT:
STEAM GENERATOR USI PROGRAM - UTILITY RESPONSES TO STAFF RECOMMENDATIONS IN GENERIC LETTER 85-02 PURPOSE: To inform the Commission of utility responses to staff recommendations stemming from steam generator Unresolved Safety Issues (USIs) A-3, A-4, and A-5.
BACKGROUND: NRC Generic Letter 85-02 was issued on April 17, 1985, to inform licensees and applicants of PWRs and Fort St. Vrain of staff recommended actions stemming from the staff's program for the . resolution of USIs A-3, A-4, and A-5 regarding' steam generator tube integrity. This letter also requested that the subject licensees and applicants provide a description of their overall programs for assuring steam generator tube integrity and for steam generator tube rupture mitigation.
The description of the plant-specific programs was requested to be of sufficient detail to permit the. staff to compare these programs with the staff recommended actions.
This paper responds to Commission directives transmitted from the Secretary to the Executive Director for Operations in a January 23, 1985 memorandum for a sumary report on the number and quality of responses received from utilities in response to the staff recommended actions. This paper also provides the staff's assessment of these responses and planned follow-up l efforts.
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l CONTACT:
l G. Holahan, ORAS/NRR x24410 i
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The Commissioners DISCUSSION: Number and Quality of Responses Utility responses to the staff recommended actions have.been received for all PWRs with the exception of plants where i construction has been delayed indefinitely. The applicants for Washington Nuclear 1 and 3 and flidland I and 2 have committed !
to submitting responses when and if construction is resumed.
A response was also submitted for the steam generators at the Fort St. Vrain gas-cooled reactor plant.
Overall., the staff believes the quality of the responses was adequate to meet the objectives of the information gathering effort; namely to gather data regarding how licensee programs and practices in certain key areas compare to the staff recommended actions in terms of the effectiveness of these approaches in ensuring steam generator tube integrity and the mitigability of steam generator tube ruptures. Where necessary, additional information concerning the licensee programs was obtained by telephone. This data has permitted the staff to !
j observe the industry-wide trends in the licensee programs in :
these areas and the variability in these programs among plants.
Considering that the licensee responses were submitted on a voluntary basis, the overall industry response to the staff's ,
l request for information must be considered good. However, caution must be exercised in drawing long range conclusions from this information since many aspects of licensee responses in z.reas addressed by the staff recommended actions go beyond current regulatory requirements. Licensees have not formally committed to continue implementation of these aspects in the future.
Also, implementing procedures, where applicable, were not reviewed by the staff.
Assessment of Utility Responses to Staff-Recommended Actions in Generic Letter 85-02 The utility responses to NRC Generic Letter 85-02 relative to each of the staff recommended actions were reviewed by the cognizant staff technical review branch for that particular issue. Where differences existed between a staff recommended action and a utility's approach (i.e., program, practice, or policy) to the area of concern addressed by the staff's recommendation, the staff evaluated the effectiveness of the utility's approach in ensuring steam generator tube integrity and/or mitigability of steam generator tube ruptures as compared to the specific actions recommended by the staff. For each plant, the licensee's approach to each area of concern was ranked by the staff as being largely consistent or equivalent; partially l
The Commissioners consistent or equivalent; or not consistent or equivalent to the staff recommended actions. It must be emphasized at'this-point that these rankings are intended only for purposes of comparison with the staff recommended actions. These rankings do not necessarily translate to adequate, partially adequate, or inadequate.
Table 1 provides an overall summary of the number of plants falling into each of the above three categories for each issue l addressed by the staff's recommended actions. It can be seen i in this table that with the exception of condenser inspection ;
programs, the large majority of licensees and applicants are !
following programs, practices, and/or procedures which appear ,
to be largely consistent with or equivalent to the staff 1 recommended actions. In addition, few licensees are following approaches which are not.at least partially consistent with or-equivalent to the staff recommended actions.
Of particular interest in Table 1 are the industry responses to the issues dealing with. the prevention and detection of loose parts (issues 1.a and 1.b), and secondary water chemistry control-(issue 4). Actions pertaining to these issues have been shown in the staff's value-impact analysis to have the greatest potential for reducing the frequency of steam generator tube rupture events and the associated potential for significant non-core melt levels of radiological releases. In addition, actions pertaining to secondary water chemistry control have been shown to have the highest. potential for producing significant reductions in occupa-tion radiological exposures. Except as noted for three plants in Table 1, all plants appear to be implementing actions and programs concerning these issues which appear to be at least 1 partially consistent with or equivalent to the staff's recommended. a actions,.with the large majority of plants implementing programs j which appear to be largely consistent or equivalent to the staff I recommendations. l The utility responses with respect to the condenser inspection issue merit discussion since mott utility practices in this area either fall short of or did not fully address the staff recomended actions. The staff believes that implementation of the staff recommended actions in this area will be beneficial in ensuring the leak tightness of the condensers as part of a successful 4 secondary water chemistry program. However, regardless of the 1 actual utility approach to condenser inspections, the key to a q v
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1 The Commissioners successful water chemistry program will be the commitment of plant management to maintaining the water chemistry to within the program specifications and taking timely corrective ection, including reductions and plant shutdowns as appropriate, for out-of-specification conditions. Thus, a commitment by plant management to a successful secondary water chemistry program, plus the desirability from an economic standpoint of minimizing power reductions and plant shutdowns provides strong incentive for implementing adequate condenser maintenance.
Another point of particular interest in Table 1 concerns the Technical Specification litits on primary to secondary leakage at Oconee Units 2 and 3. Because secondary water chemistry and steam generator tube inspection programs have not been successful in totally eliminating primary to secondary leakage, Technical Specification limits on allowable primary to secondary leakage have been relied upon to ensure that the plant will be shytdown for appropriate corrective action before an SGTR occurs. With the exception of Oconee Units 2 and 3, Technical Specification leakage limits for an individual steam generator generally range among plants from 0.1 gallons per minute (gpm) to 1.0 gpm. (The staff recommended limit is about 0.35 gpm per steam generator).
The plant Technical Specification limit for Oconee Units 2 and 3 1s 10.0 gpm which the staff does not consider to be a sufficiently effective limit for preventing tube ruptures. Although the licensee, in practice, has normally initiated a plant shutdown when the measured leak rate reaches 0.3 to 0.5 gpm, the staff has initiated discussions with the licensee for changes to the plant Technical Specifications to incorporate an acceptable limit.
None of the staff's findings in Table 1 are indicative, in-and-of-themselves, of significant risk, and with the exception of primary to secondary leak rate limits for Oconee Units 2 and 3, none are indicative of areas requiring formal regulatory action at this time. The staff's findings, however, are indicative of areas where the effectiveness of overall plant-specific programs can be improved. The staff will inform licensees of its findings relative to their plants and will continue to encourage utilities to implement the staff's recommendations or appropriate alter-natives.
As has been previously reported to the Commission, the staff has concluded that steam generator tube rupture events are not a major contributor to overall risk from nuclear power plants. Industry trends toward implementation of more effective preventive maintenance programs will serve to counteract the effects of increasing age and attendant accumulated mechanical and corrosion-induced degradation of the steam generators, and thur will provide added assurance that risk will continue to be small.
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. The Commissioners However, it is important to recognize that SGTR events are not l an inherent " low risk" issue. Rather, low risk is assured only
'through implementation of programs which are effective.in ensuring steam generator- tube integrity and SGTR mitigability. As has been true in the past, utilities must be vigilant against new or unusual problems which may. necessitate preventive, diagnostic, and/or corrective actions beyond normal utility practices and/or regulatory requirements. The staff will continue to monitor steam generator operating experiences as an indicator of the effectiveness of utility programs. Again, as has been the case in the past, the staff may require additional actions on a plant-specific basis in cases of severe or extensive degradation where such actions are needed to provide continued assurance of low risk and compliance with the regulations. Any such requirements would of course, be subject to the Commission's backfit rule as applicable.
SUMMARY
AND CONCLUSIONS: '1. . Licensees and applicants for all PWRs and . Fort St. Vrain provided responses to the staff recommended actions.
The quality of the responses were generally adequate to meet the objectives of the infonnation-gathering effort.
- 2. The responses indicate that the large majority of the licensees and applicants are following programs, practices, and/or procedures which are partially to fully consistent or equivalent to the staff recommended actions. It appears that both industry initiazive and the staff recommendations have been responsible for significant improvements over the past few years.
- 3. The staff will continue to monitor operating experience.
As in the past .the staff may require additional actions on a plant-specific basis in instances of severe or extensive degradation as needed to ensure continued safe !
operation of the plant. Such requirements would be subject ,
to the Commission's backfit rule where applicable, ,
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. The Commissioners s
- 4. Changes to the Technical Specification limits on primary-to secondary leakage for Oconee Units 2 and 3 are necessary to ensure that appropriate corrective actions are taken before rupture occurs. The staff is currently discussing the needed changes with the licensee.
- 5. The staff will issue its findings regarding the individual utility responses to NRC Generic Letter 85-02 to the respective utilities. Licensees will be encouraged to upgrade their program as needed to meet the intent of the staff's recomended actions; however, this will not be a requirement. .l
- 6. -The staff recommended actions will be used as review guidance for OL applicants; however, applicants would be required to make programmatic changes only where these changes- l are found to be consistent with the Comission's backfit rule.
In order to ensure consistency among staff guidance documents in these areas, the Standard Review Plan and Standard Technical Specifications will be revised as necessary to be consistent with the Staff recomended actions.
- 7. The staff's program document for resolving USI's A-3, A-4, and A-5 is being updated to reflect the staff's findings from the information-gathering effort herein.
This document, NUREG-0844, was issued in draft form for public coment in April 1985 and is scheduled for final publication in April 1986. Final publication for NUREG-0844 will constitute final resolution of USI's A-3, A-4, and A-5 regarding steam generator tube integrity.
- f ,- e f5 Victor Stello,/Jr.
Acting Executive Director j for Operations j
Enclosure:
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