ML20115D348
| ML20115D348 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 07/10/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20115D343 | List: |
| References | |
| NUDOCS 9607150125 | |
| Download: ML20115D348 (4) | |
Text
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UNITED STATES l
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j NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20066-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.147 TO FACILITY OPERATING LICENSE NO. OPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION i
VERMONT YANKEE NUCLEAR POWER STATION i
DOCKET NO. 50-271 l
1.0 INTRODUCTION
By letter dated April 4,1996, the Vermont Yankee Nuclear Power Corporation (the licensee) submitted a request for changes to the Vermont Yankee Nuclear Power Station (VYNPS) Technical Specifications (TSs). The requested changes would revise the TS regarding secondary containment integrity including addition of required actions in the event secondary containment integrity is not maintained when required.
They also would require surveillance of the secondary containment isolation valves under the VYNPS in-service testing program.
The safety objectives of the secondary containment are to minimize ground level release of airborne radioactive materials and to provide a means for a controlled release of the building atmosphere should a design basis accident occur. There are two principal accidents for which credit is taken for secondary containment integrity. These are the loss-of-coolant accident (LOCA) and the refueling accident.
The analysis of these accidents is discussed in the VYNPS Final Safety Analysis Report (FSAR) section 14.6.
The secondary containment performs no active function in response to either of these limiting events, however, leak tightness is required to ensure that the release of radioactive materials from the primary containment is restricted to those leakage paths and associated leakage rates assumed in the accident analysis and that fission products entrapped in the secondary containment will be treated by the standby gas treatment system (SGTS) prior to discharge to the environment. The secondary containment system is described in VYNPS FSAR section 5.3.
2.0 EVALUATION The licensee proposed to revise TS 3.7.C.1 regarding requirements for integrity of secondary containment. The current requirement specifies four conditions which must all be met to allow relaxation of secondary containment. These requirements are that a) the reactor is subcritical with sufficient shutdown margin; b) reactor coolant water temperature is less than 212 "F and the reactor coolant system is vented; c) no activity is being performed which could reduce the shutdown margin; and d) tha fuel cask or irradiated fuel is not being moved in the Reactor Building. The proposed TS 3.7.C.1 specifies four conditions or activities during any of which secondary containment integrity shall be maintained. These are a) whenever the reactor is in the run mode, startup mode, l
or hot shutdown condition; b) during movement of irradiated fuel assemblies or 9607150125 960710 PDR ADOCK 95000271 P
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r C l the fuel cask in secondary containment; c) during alteration of the reactor core; and d) during operations with potential for draining the reactor vessel (0PDRVs).
During operation in the run or startup modes (as defined in VYNPS TS 1.0.R) or in the hot shutdown condition (as defined in VYNPS TS 1.0.V.1), a LOCA could lead to fission product release to the primary containment which could leak to the secondary containment. Secondary containment integrity is required during operation in these conditions.
Therefore, the staff finds proposed TS 3.7.C.I.a acceptable.
During operation in the cold shutdown condition (as defined in VYNPS TS 1.0.V.2) or in the refuel mode (based on mode-selector-switch position as defined in VYNPS TS 1.0.J), the probability and consequences of the LOCA are reduced due to the pressure and temperature limitations in those modes. Therefore, maintaining i
secondary containment integrity (to ensure a control volume) is not required, except during specified activities for which significant releases of radioactive material can be postulated, such as during OPDRVs, during alterations of the reactor core, or during movement of irradiated fuel assemblies or the fuel cask l
During these activities, secondary containment integrity is required. Therefore, the staff finds proposed TS 3.7.C.1.b through i
3.7.C.1.d acceptable.
I Proposed TS 3.7.C.2, 3.7.C.3 and 3.7.C.4 provide new required actions when secondary containment integrity is required but cannot be maintained or restored.
If secondary containment integrity is not maintained, it must be restored within l
4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (proposed TS 3.7.C.2).
This provides a brief period of time to correct a l
problem that is commensurate with the importance of maintaining secondary i
containment integrity during operation in the run or startup mode or in the hot shutdown condition.
This time period also ensures that the likelihood of an accident requiring secondary containment integrity occurring during periods where secondary containment integrity is not maintained is minimal. Therefore, the staff finds proposed TS 3.7.C.2 acceptable.
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If secondary containment integrity cannot be restored within the required time of TS 3.7.C.2, the reactor must be in the hot shutdown condition within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and the cold shutdown condition within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. These times are reasonable, based on operating experience to reach the required plant condition from full power operation in an orderly manner and without unnecessarily challenging plant systems. Therefore, the staff finds proposed TS 3.7.C.3 acceptable.
Movement of irradiated fuel assemblies or the fuel cask in the secondary containment, alterations of the reactor core (as defined in TS 1.0.B), and OPDRVs can be postulated to cause fission product release to the secondary containment.
In such cases, the secondary containment is the only barrier to the release of fission products to the environment. Alterations of the reactor core and movement of fuel assemblies or the fuel cask must be immediately suspended if secondary containment integrity is not maintained.
Suspension of these activities shall not preclude completing an action that involves moving a component to a safe position. Also, action must be initiated to suspend OPDRVs
l l to minimize the probability of a vessel draindown and subsequent potential for fission product release. Actions must continue until 0PDRVs are suspended.
l Therefore, the staff finds proposed TS 3.7.C.4 acceptable.
A new TS 4.7.C.1.d is proposed'which would require operability testing of reactor building automatic ventilation system isolation valves in accordance with the VYNPS in-service testing program.
Implementation of this testing requirement will demonstrate the operability of these isolation valves and therefore the staff finds proposed TS 4.7.C.I.d acceptable.
The licensee proposed to revise the applicability of TS 3.7.B.1 for the SGTS to include the hot shutdown and cold shutdown conditions to remain consistent with l
the proposed changes to TS 3.7.C.1.
This change clarifies the requirements for SGTS availability and ensures that they are consistent with the requirements for secondary containment integrity and therefore the staff finds proposed TS 3.7.B.1 acceptable.
l The licensee proposed to revise the numbering of existing TS 3/4.7.C.2 to i
3/4.7.C 5 to accommodate the proposed changes to TS 3/4.7.C.1.
In addition, the licensee proposed to add TS 4.7.C.2 through 4.7.C.4 as " Intentionally blank" to maintain consistency between new TS 3.7.C.5 and 4.7.C.5.
These changes are editorial and are therefore acceptable.
'The license proposed changes to the Bases for TS 3.7.8 and C and 4.7.B and C to address the proposed changes to those TS. The staff has reviewed the proposed Bases changes and has no objection to them.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Vermont State official was notified of the proposed issuance of the amendment.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes requirements with respect to installation or use of I
facility components located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has 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 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 (61 FR 20859). 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.
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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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
l Principal Contributor:
D. Dorman Date:
July 10, 1996 f
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