ML20247K154
| ML20247K154 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/16/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20247K149 | List: |
| References | |
| NUDOCS 8906010231 | |
| Download: ML20247K154 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION r,
- l WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 45 TO FACILITY OPERATING LICENSE NO. NPF-30 UNION ELECTRIC COMPANY CALLAWAY PLANT. UNIT I DOCKET NO. STN 50-483 1.0. INTRODUCTION Callaway License Condition 2.C.(11) states:
" Prior to restart following the first refueling outage, UE shall submit for NRC review and approval an analysis which demonstrates that the steam generator single-tube rupture (SGTR) analysis presented in the FSAR is the most severe case with respect to the release of fission products and calculated doses. Consistent with the analytical assumptions, the licensee shall propose all necessary changes to Appendix A to this license".
The required SGTR analysis was submitted by letter dated January 8,1986 and supplemented with additional letters. This analysis takes credit for the operation of an Atmospheric Steam Dump (ASD) to mitigate the consequence of a SGTR accident. Since the ASD's have not previously been relied upon to mitigate postulated accidents and transients, there are currently no require-ments relating to operability of the ASD's in the Callaway Technical Specifi-cations (TS). Therefore, by letter dated January 14, 1986, the licensee submitted proposed TS that require ASD operability.
2.0 DISCUSSION The NRC staff is currently reviewing two separate concerns relating to l
License Condition 2.C.(11) of Operating License No. NPF-30. The first concern is the SGTR accident analysis. Two scenarios were analyzed as rerluested by the staff: the scenario'inost conducive to steam generator overfill, and the scenario that maximizes offsite dose. With regard to the SGTR analysis, the staff is currently examining assumptions being used for operator action times used in the analysis. The secord concern of the License Condition is the proposed TS for ASD operability. 'The staff is handling the two concerns separately and will address the acceptability of the' SGTR analysis in future correspondence.
By letter dated March 21, 1989, the staff provided the results of the review of the licensee's submittal of January 14, 1986.
In summary, the staff did not find the proposed TS to be acceptable. Areas of concern included the time interval allowed for inoperability of a single ASD and operability with an ASD isolated (via closure of the upstream block valve) due to excessive lea kage.
Included in the staff's response were alternatives that the staff felt would provide acceptable reliability of the ASD's for SGTR accident mitigation. By ' letter dated April 14, 1989, the licensee responded to the staff position with revised TS for the ASD's.
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. 3.0 EVALUATION The Callaway Plant design includes four ASD's, one ASD fet each steam gener-ator. The operability of at least three of the four ASD's ensures that reactor decay heat can be dissipated to the atmosphere in the event of a SGTR coincident with a loss of offsite power.
Reactor Coolant System (RCS) cooling can subsequently be performed through Residual Heat Removal System (RHR) operation.
For RCS cooldown to RHR system initiation, only one ASD is required, Three operable ASD's are adequate, assuming that one of the operable ASD's is on the faulted steam generator, and thus unavailable for heat removal, and that one ASD fails to function in accordance with single failure assumptions.
The proposed TS are only applicable in plant operational Modes 1, 2, and 3.
The purpose of the ASD's is to provide for removal of decay heat during the initial phases of the SGTR event up to RHR system initiation. Since the RHR system is available in Moces 4, 5, and 6, these TS are only applicable in Modes 1, 2, and 3.
Each ASD is equipped with a manual block valve, located near the ASD in the auxiliary building, to provide a positive shutoff capability should an ASD develop leakage. Closure of the block valves of all ASD's because of excessive seat leakage does not endanger the reactor core because decay heat can be dissipated with the steam line safety valves. Also, consistent with SGTR analysis assumptions, a block valve can be used to control release of steam to the atmosphere.
The LC0 Action statements included in the revised TS are consistent with those provided in the NRC st6ff position. The new proposed requirements state that three of the four steam generator ASD's shall be operable in Modes 1, 2, and 3.
If only two ASD's are operable, this specification allows 7 days to return one of the two inoperable ASD's to operable status.
If only one or no ASD is operable, this specification allows only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to return at least two ASD's to operable status.
If one or more of the required ASD's are inoperable due to excessive seat leakage, the associated upstream block valve may be closed. With the block valve closed, the specification allows 30 days to restore the required number of ASD's to operable status.
The restoration tine periods provided in the proposed LC0 Action statement are based on the low likelihood of having a SGTR event coincident with a loss of offsite power during the time period that one or more of the required ASD's is out of service. Theallowedtimeperiod(7 days)forthecaseof one inoperable ASD is longer than the time period (24 nours) allowed when more than one ASD is inoperable.
l The licensee's letter dated May 5,1989, clarifies earlier discussion in the April 14, 1969 letter regarding testing of the ASD's at power. Testing is normally done during Mode 3 to preclude plant transients associated with cycling the valves and it is done in accordance with the NRC approved Callaway Inservice Testing Program. The staff considers the surveillance requirements of the Callaway Inservice Testing Program for ASME Code valves appropriate I
and sufficient for the ASD's. Therefore, the surveillance requirements in the proposed TS refer to the provisions of existing specification 4.0.5.
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.. The licensee's revised TS submittal of April 14, 1989 is consistent with the staff's position regarding the operability of the ASD's. We consider l
the reviseo TS acceptable and appropriate for reliable mitigation of a steam-generator-tube-rupture event. The TS requirements constitute additional limitations on facility operations and satisfy, in part, the specific require-mentsofLicenseCondition2.C.(11)oftheoperatinglicense. Therefore, based upon our review of the licensee's submittal, we find the proposed TS changes regarding the ASD's to be acceptable.
The staff alsu notes that the licensee propored a wording change to remote shutdown instrumentation specification to provide consistent use of the term " atmospheric steam dump". The staff finds this change to be administra-tive in nature and, therefore, acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to a requirement with respect to the instal-1ation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or o change to a surveillance requirement. The 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 radinion exposure. The Commission has previously issued a proposed finding that this amendment involves ne significant hazards consideration and there has been no public comment on sucq finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuantto10CFR51.22(b),noenvironmental impact statement or environmental ossessment need be prepared in connection with the issuance of this amendment.
5.0 CONCLUSION
The staff 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; and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense dnd security or to the health and safety of the public.
Principal Contributors:
K. Desai, SRXB, T. Alexion, FDIII-3 Dated: May 16, 1989