ML19257B080
| ML19257B080 | |
| Person / Time | |
|---|---|
| Issue date: | 07/10/1978 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Mattson R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML111230364 | List: |
| References | |
| REF-GTECI-A-22, REF-GTECI-CO, REF-GTECI-FU, REF-GTECI-RV, REF-GTECI-SY, TASK-A-22, TASK-OR NUDOCS 8001150201 | |
| Download: ML19257B080 (3) | |
Text
jN UNITED STATES NUCLEAR REGULATORY COMMISslON M.pt,j y-j,
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WASHINGTON, D. C. 20555 q..
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JUL 10 1978 10RANDUM FOR: Roger J. Mattson, Director Division of Systems Safety FROM:
Robert L. Tedesco, Assistant Director for Plant Systems Division of Systems Safety
SUBJECT:
CLASSIFICATION OF MAIN FEEDWATER ISOLATION VALVES FOR PRESSURIZED WATER REACTORS STATEMENT OF ISSUE Non-safety grade components of the main feedwater system for pressurized water reactors that are upstream of the containment isolation valves are classified Quality Group D and are constructed to the applicable component codes and standards in Table 1 of Regulatory Guide 1.26.
These components are not designed for the safe shutdown earthquake (seismic Category I) as defined in Regulatory Guide 1.29.
Thus, the main feedwater control valves which may be used to perform a safety function as a bac;.up valve to the main feedwater isolation valve is a Quality Group D component.
Applicants in many recent licensing applications have utilized a backup valve which is classified Quality Group B.
Other Applicants such as Toledo Edison Co. (Davis Besse 2 & 3) propose to utilize the feedwater control valve as the backup valve.
Pending resolution of Task Action Plan A-22 which will resolve this issue, the Auxiliary Systems Branch has developed an interim position which is discussed below.
AUXILIARY SYSTEMS BRANCH INTERIM POSITION In the case of isolation of feedwater to the steam generators, should an applicant add an additional backup isolation valve or simply upgrade the main feedwater control valve to " safety grade" quality, the components (interconnecting piping and valve) should be classified Quality Group B, (constructed to ASME Section III, Class 2), and designed to seismic Category I requirements.
By imposing seismic Category I requirements on these components, we assure the quality assurance requirements of Appendix B to 10 CFR Part 50 are applied, in conformance with Regulatory Guide 1.29.
CONTACT:
RKirkwood, ASB X27763 1750 002 8001150 A O /
e ML 101978 Roger J. Mattson For construction permits, we should require an applicant to commit to Quality Group B and seismic Category I design requirements for the addi-tional backup isolation valve or main feedwater control valve; however, this requirement would De reevaluated at the operating license stage in conjunction with the resolution of Task Action Plan A-22, "PWR Main Steam Line Break, Core, Reactor Vessel, and Containment Building Response."
Included in this evaluation would be the need for reliance on nonsafety For plants under review grade components to perform a backup function.
for operating licenses, where the feedwater control valve may also be used as a backup valve, it should not be required to meet seismic Category I requirements or the quality assurance program of Appendix B In this instance, a Quality Group D valve would to 10 CFR Part 50.
This classification would be sufficient pending completion of suffice.
Task Action Plan A-22 dealing with the question on the use of nonsafety In this case, it seems appropriate not to require that a grade equipment.
new valve of safety grade quality be provided in a plant late in design Should the outcome of Task and construction when it may not be necessary.
Action Plan A-22 indicate otherwise then backfit action could be taken on all plants according to Section 50.109 of 10 CFR Part 50.
BACKGROUND As noted in NUREG-0138, in the event of a steam line break inside contain-ment, it is necessary to isolate the main feedwater to the steam generator associated with the failed line to preclude overpressurizing the contain-If the single active failure ment and to limit the reactivity transient.
postulated for this accident is the failure of the appropriate safety grade main feedwater isolation valve to function, then credit is taken Reliance for closing the nonsafety grade main feedwater control vahe.
on this nonsafety grade valve in the postulated accident evaluation is permitted based on the reliability of these valves.
The staff believes that it is acceptable to rely on the nonsafety grade main feedwater control valve as a backup because its design and perfor-mance is compatible with the accident conditions for which it is called The staff position is that utilization of the main feed-water control valve as a backup to a single failure in safety grade components upon to function.
Except for the Auxiliary Feedwater System, Quality Group C is normally used for conponents and piping in safety related systems of NOTE:
Although Quality Group C components are designed to the requirements of ASME Section III, Class 3, the Appendix B quality moderate energy.
assurance program is only applicable when the components are designed to seismic Category I requirements. To design the backup valve to Quality Group C requirements would create a hybrid situation.
1750 003
JUL 101978
. Roger J. Mattsor.
-3_
adequately protects the health and safety of the public. This matter is the subject of Task Action Plan A-22.
M>
R. L. Tedesco, Assistant Director for Plant Systems Division of Systems Safety cc:
T. Novak V. Benaroya G. Lainas D. Ross R. Kirkwood J. Glynn C. Long 1750 004