ML20114B311
| ML20114B311 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/10/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20114B308 | List: |
| References | |
| NUDOCS 9208260056 | |
| Download: ML20114B311 (3) | |
Text
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ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.161 TO FACILITY OPERATING LICENSE NO. OPR-77 AND AMENDMENT NO.151 TO FAClllTY OPERATING LICENSE NO. DPR-71 TENNESSEE VALLEY AUTHORITY SE000YAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
By application dated May 26, 1992, the Tennessee Valley Authority (the licensee) proposed an amendment to the Technical Specifications (TS) for Sequoyah Nuclear Plari (SQN) Units 1 and 2.
The requested changes would revise the TS to provide additional requirements designed to ensure operability of the ice condenser doors. The licensee has proposed re-labeling the existing Limiting Condition for Operation (LCO) 3.6.5.3 to 3.6.5.3.b and inserting a new LC0 numbered 3.6.5.3.a.
In addition, a proposed change to Surveillance Requirement 4.6.5.3.1.b.2 would verify that opening of each door is not impaired by an " obstruction," in addition to the items that are presently verified (ice, frost, and debris) at 18-month intervals.
The proposed change to Bases 3/4.6.5.3 would emphasize the importance of maintaining the inlet doors free to open and the need to take immediate corrective action.
2.0 EVALUATION The ice condenser is a passive device located inside the primary containment.
It contains borated ice that is used in the event of a loss of coolant
. accident (LOCA) or high energy line break (HELB) to absorb the thermal energy that would be released by condensing the steam that would be released as a result cf the accident. The resulting pressure reduction, along with the containment spray system, ensures the integrity of the containment during the early stages of the accident.
It also reduces the fission product iodine concentration in the post-LOCA and/or post-HELB containment atmosphere.
The ice condenser is divided into 24 bays, with each bay having a pair of inlat doors in the lower compartment.
These doors are designed to be opened by the differential pressure produced by the LOCA or HELB, which allows the 9208260056 920010 PDR ADOCK 05000327 P
steam and air to flow through the condenser. The inlet doors are normally closed to form a barrier to the containment atmosphere during normal plant operation, and they are maintained closed by tension spring mechanisms that produce a small closing torque.
This prevents excessive loss of ice during normal plant operation.
The present TS LCO 3.6.5.3 requires that if one or more of the ice condenser doors is open or otherwise inoperable, power operation can continue for 14 d.ys provided that the ice bed temperature is monitored at least once per 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and that the niaximum ice bed temperature is maintained less than or equal to 27'F.
Otherwise, the doors must be closed or made operable (as appropriate) within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or the plant placed in the Hot Standby condition within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in the Cold Shutdown condition within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. This LCO would remain, but would be relabeled 3.6.5.3.b.
The new LC0 proposed by the licensee would become 3.6.5.3.a and would require that if one or more of the ice condenser inlet doors are inoperable because they are physically restrained from opening, the inlet door (s) must be restored to the operable status witidn one hour or the plant placed in at least the Hot Standby condition within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in the Cold Shutdown condition within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The purpose of the new LCO is to provide actions that address the potential for the inlet doors to be physically restrained from opening and, therefore, not capable of automatically opening when required.
The present LC0 is appropriate to address the required actions shculd one or more of the doors be open..However, it is nonconservative in that it does not provide appropriate actions should one or more (up to all) of the doors be blocked from opening. Allowing the doors to remain in this condition for the 14 days is not appropriate and is potentially more serious from a plant risk perspective since the ice condenser system may not be capable of performing its safety-related function of reducing the primary containment pressure following a LOCA or HELB.
The new LC0 addresses this concern by allowing plant-operation for only one hour under this condition, and is consistent with Revision 4a of the Westinghouse Standard Technical Specifications dated September 1987.
In an effort to determine that opening of the doors is not impaired, the licensee proposed addition of a check to ensure that an obstruction does not exist, in addition to the present requirement to check for ice, frost and debris when the surveillance test is performed. This represents a more conservative approach to the surveillance test that is performed at 18-month interval s.
Since the proposed changes appropriately reflect the additional operability concerns of the ice condenser doors, represent an increase in the safety-related aspects of plant operation, a more conservative approach, and is consistent with staff guidance, the staff has determined that they are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official was notified of the p*oposed issuance of the aw ndments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change 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 to the surveillance requirements.
The NRC staff has determined that the amendments involve 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 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 (57 FR 30262). Accordingly, the amendments meet 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 er environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The Commission has 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, -(2) such activities will.be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to.the common defense and security or to the health and safety of the public.
Principal Contributor:
D. LaBarge Date: August 10, 1992 m