ML19350C133
| ML19350C133 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 03/23/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19350C132 | List: |
| References | |
| NUDOCS 8103300568 | |
| Download: ML19350C133 (2) | |
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NUCLEAR REGULATORY COMMISSION 3.' - '
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w SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 66 TO LICENSE NO. DPR-49 IOWA ELECTRIC LIGHT AND POWER COMPANY CENTRAL IOWA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DOCKET N0. 50-331 DUANE ARNOLD ENERGY CENTER Introduction The Duane Arnold plant has a two inch nitrogen line penetrating the drywell that serves an instrument air function. This line serves the solenoid operated main steam isolation valves and valves in the ECCS piping.
Considered a nonessential system, this line is automatically isolated by a Group 3 containment isolation signal which can be actuated by either a high radiation signal, high drywell pressure or low reactor water level.
The containment isolation valve inside the drywell for this nitrogen line is a power operated diaphragm valve. This valve fails in the closed position and is reopened by pressure from the nitrogen system.
If this diaphragm valve closes and fails to reopen, the downstream nitrogen pressure would begin to decay resulting in gradual closure of the MSIVs and eventual plant trip. Reopening of this valve would require deinerting of the drysell and personnel entry.
In a letter dated February 20, 1981, Iowa Electric Light and Power Company (licensee) proposed replacing the' nitrogen supply power operated valve with a stop check valve. This change is being requested to reduce the potential of forced outages and inadvertent plant scrams due to a failure of the diaphragm valve. This change would modify tables in the plant's
' Technical Specifications that identify (1) containment isolation valves that must be leak tested and (2) primary containment power operated isolation valves.
Evaluation The licensee states that the stop check valve (#V-43-214) will be purchased to the same codes and specifications as the original diaphragm valve
(#CV-4371-8). The stop check valve will he locally leak tested as required
.by Appendix J to 10 CFR Part 50. Replacement of a diaphragm valve with a stop check valve inside containment is permissible under General Design -
Criteria 56, " Primary Containment Isolation."
J10 3 3 0 056
, Replacement of the diaphragm valve with the stop check valve does not require staff approval. However, the change in valve numbers necessi-tates a revision to the plant's Technical Specifications.
We have reviewed the proposed revisions to the plant's Technical Specifi-cations and find them acceptable. We conclude that the change of valve type in the nitrogen line should enhance plant operability.
Environmenta' Considerations We have determined that the amendment does not involve a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR Section Sl.5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
Conclusions We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the endangered by operation in the proposed manner, and (3)public will not be such activities will be conducted in compliance with the Commission's regulations and the issuance of the amendment will not be inimical to the common defense and security or_ to the health and safety of the public.
Dated: March 23,1981.
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