ML20235S478
| ML20235S478 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 09/30/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20235S470 | List: |
| References | |
| NUDOCS 8710090015 | |
| Download: ML20235S478 (3) | |
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UNITED STATES
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g NUCLEAR REGULATORY COMMISSION p
WASHINGTON, D. C. 20555 kJ [
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.146 TO FACILITY OPERATING LICENSE NO. DPR-49 j
IOWA ELECTRIC LIGHT AND POWER COMPANY CENTRAL IOWA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DUANE ARNOLD ENERGY CENTER J
DOCKET NO. 50-331 j
- 1. 0 INTRODUCTION A general letter to all utilities dated November 29, 1978, identified two areas of concern associated with operation of the containment vent and purge valves while the plant is at power.
The concerns relate to
- 1) a design basis loss of coolant accident (LOCA) occurring while the j
isolation signals for opening the vent / purge valves are overridden, and
- 2) a design basis LOCA occurring during vent / purge valve operation.
Both of these events could produce unacceptable radioactive releases.
In response to the general letter, Iowa Electric Light and Power Company (the licensee) provided information concerning the operation of their vent and purge valves. Upon review of these submittals, the NRC staff issued safety evaluation reports on June 3, 1981, January 20, March 29, May 22, and October 1, 1984, in which it was noted that the licensee's approach was acceptable, pending submittal of acceptable modifications to the plant Technical Specifications.
By a letter dated April 5, 1985, which was superseded by a letter dated i
December 18, 1986, the licensee submitted proposed modifications to their d
plant Technical Specifications in accordance with the staff's guidance, i
as provided in the general letter.
This evaluation deals with the p
acceptability of the proposed Technical Specification changes.
2.0 EVALUATION The April 5, 1985 submittal proposed changes to 1) plant Technical i
Specifications 3.7.A.9 and 3.7.A.10, which limit the time that the vent / purge valves can De opened and the related reporting requirements, respectively, 2) Table 3.7-2, which identifies the maximum valve opening angle to be 30 degrees and a listing of the affected valves, and 3)
Technical Specification 3/4.7,0.2, which deals with the operability of the valves and acceptable methods for their isolation.
Our review of the submittal indicated that there were some containment vent and purge valves which were not identified in the proposed Technical Specifications.
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Furthermore, the wording in some of the proposed Technical Specifications was ambiguous.
To rectify these concerns, the licensee provided revised proposed Technical Specifications in a submittal dated December 18, 1986.
Limitation on use of the Vent and Purge Valves A design basis LOCA, occurring while the vent or purge valves are open, could result in an uncontrolled release of the containment atmosphere to the environment.
To reduce the probability of this, the licensee provided Technical Specifications 3.7.A.9 and 3.7.A.10 (incorporated in the license by Amendment No. 100).
Specifically, 3.7.A.9 dealt with limiting the operational time to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year, and 3.7.A.10 dealt with the reporting requirements in the event that the requirements of 3.7.A.9 could not be met.
Our October 1, 1984 SER i
concluded that the vent and purge valves could close against the pressures associated with the design basis LOCA environment.
Subse-quently, the licensee has modified the standby gas treatment system (SGTS) such that overpressure would not damage either train of the SGTS in the unlikely event of the design basis LOCA occurring during vent or purge operations. On the basis of the valves' ability to close against the containment pressure from a LOCA, and since the SGTS has been modified to withstand the pressure buildup while the valves are closing, the licensee has proposed deleting these two specifications.
The licensee has proposed a new Specification 3.7.A.9 as a replacement.
The new specification identifies the containment vent and purge valves and specifies that they "may not be opened so as to create a flow path from the primary containment while primary containment integrity is required except for inerting, de-inerting, i
vent / purge valve testing, or pressure control".
Since the vent and purge valves can be closed against the containment LOCA pressure, no post accident degradation of the SGTS ductwork outside containment is 4
expected.
Also, the licensee has followed the NRC staff's guidelines as outlined in the general letter.
Hence, we find that the licensee's proposed modifications to Technical Specifications 3.7.A.9 and 3.7.A.10 are acceptable.
Surveillance of Mechanical Opening Limitation of 18-Inch Valves An NRC staff SER concerning the operability of the mechanical stop for the vent and purge valves was issued to the licensee on October 1, 1984.
As indicated in this SER, the staff found that all 18-inch vent and purge valves would be operable in the event of a LOCA if the open travel was limited to 30 degrees.
In order to bring the plant Technical Specifications into conformance with the October 1,-1984 findings, the licensee has proposed modifying Technical Specification Table 3.7-2.
The proposed modification requires the 18-inch vent and purge valves to have mechanical stops which limit the maximum valve opening to 30 degrees.
Since the proposed Technical Specification modifications bring the plant Technical g
Specifications into conformance with the guidelines provided by the staff, we conclude that.the proposed Technical Specification modifications are acceptable.
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Inoperable Primary Containment Power Operated Isolation Valves As noted above, the licensee has proposed the elimination of the Technical Specification which had limited the maximum acceptable operation time for the vent and purge valves.
In view of this, the licensee has proposed a revision to Technical Specification 3.7.D.2 to reflect more closely the wordisp of the Standard Technical Specifications.
This revision requires the restoring of the inoperable i
valves to operable status.
It also clarifies the acceptable method for providing isolation of the affected lines which contain inoperable valves.
Since this Technical Specification deals with action to be' taken in the event that a valve becomes inoperable, there is no need for surveillance requirement 4.7.D.2.
Hence, 4.7.D.2 has been deleted by the licensee.
On the basis that the proposed Technical Specification 3/4.7.D.2 conforms to the guidelines of the Standard Technical Specification, we find that it is acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.
We have determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase I
in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement'or environmental assessment need be prepared in connection with the issuance of the amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) 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.
Principal Contributor:
J. Ridgely Dated: September 30, 1987 i
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