ML20066J171
| ML20066J171 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/20/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20066J168 | List: |
| References | |
| NUDOCS 9102260014 | |
| Download: ML20066J171 (5) | |
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/.[pneayk UNITED STATES g
NUCLEAR REGULATORY COMMISSION
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W ASHING TON, D. C. 20555 SAFETY EVALUATION BY-THE OFFICE OF. NUCLEAR. REACTOR REGULATION
- RELATED T0 AMENDMENT NO.151 TO FACILITY OPERATING LICENSE NO. DpR-53 EALTINORE GA_S AND ELECTRICnCOMPAN!
CALVERT CLIFFS NUCLEAR-POWER PLANT, UNIT 1 DOCKET NO. 50-317 1.0 _ INTR 0DUC_ TION By letter dated February 8,1991, Baltimore Gas and Electric (BG&E) Company requested an emergency amendment to its Facility Operating License No. DPR-53 for Calvert Cliffs, Unit No.1, to allow operation of the unit for the remainder af the current fuel cycle with the center Control Element Assembly (CEA) excluded from its current operability ano alignment recuirements.
The request is only needed for the remainder of the Unit 1 Cycle 10, because the center CEA will be replaced during the next refueling outage for the-upcoming Cycle 11 operation. Specifically, BG&E proposes changes to Technical Specifications 4.1.1.1.1, a.1.1.2, 3.1.3.1, 4.1.3.1.1, 4.1.3.1.7, 4.1.3.1.3, '.1.3.3, 4.1.3.3.1, 4.1.3.3.2, 3.1.3.4, 4.1.3.4, 4.1.3.5, 3.10.1, 4.10.1.1.-and 4.ls.1.2, which consists of a footnote excluding the applicability of the Technical Specifications to the center CEA for Cycle 10.
Technical Specifications 3.1.3.6 and 4.1.3.6
-do not specifica71y deal with single CEAs; however, a footnote is requested to permit the exclusion of the center CEA from the determination of CEA Bank 5 position. The proposed changes to Technical Specifications 3.2.2.1, 4.2.1.3, 4.2.2.1.3, 4.2.2.3, 3.2.3, and 4.2.3.3 censist of a footnote which permits exclusion of the center CEA from the stated full lengtn CEA insertion limit.
BG&E'. request to process this amendment on an emercency basis is due to the failure of.the center CEA to fully insert during the shutdown of Unit 1 on-February 2,-1991.
BG&E discovered that the rod bottom light and the lower electric limit light, which provided indication of full insertion, had not energized for the center CEA after it had been oriven into the core.
Subsequent testing has' led to the conclusion that the center CEA is binding in the buffer region of the guide tube due to swelling of the tips of the control rod fingers.
The center CEA has been declared inoperable because BG&E cannot determine that it will continue to satisfy the rod drop time surveillance ruuirements due to the binding problem when the center CEA approaches the fully inserted position.
The determination that the center CEA is-inoperable resulted in BG&E requesting a Temporary Waiver of Compliance (TWOC) on February 8,1991.
The NRC staff reviewed the requested TWOC and granted it by letter dated February 8, 1991.
The TWOC became effective as 01a00 bcurs cn February 8, 1991, and will expire upon issaance of this requested amendment.
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'. 2.0 EVALUATION Unit I normally operates with all CEAs essentially fully out, including control Bank 5 the last bank withdrawn on approach to full power.
The center CEA is a member of Bank 5.
It is the onl BG&E concludes, and staff agrees, y " weak" CEA in Bank 5 and in the core.
that the most probable source of the swelling is.the Zircaloy (Ir) slugs in the center CEA fingers, due to hydriding of the slugs.
There are no other CEAs with Zr slugs having the potential for swelling. This CEA
-is desig(early in a 24-month cycle) power distribution control.ned as a unique " we of the Unit 1 is now about halfway through Cycle 10. The CEA is unusual in that only-the center finger of the five finger configuration contains control material. The outer four fingers contain non-control material, including a Zr slug at the bottom tip of the fingers.
It is noted that the center CEA, because of reduced absorption, has a low reactivity worth relative to other control rods (with B times the control material inventory) and shutdown rods (which are " double strength" rods covering two fuel assemblies).
Furthermore, its worth is reduced because it is in a low worth twice-burned fuel assembly. BG&E !hus concluded that the reactivity and associated power distribution effects from misalignment would be expected to be minor.
Staff finds that this conclusion is valid.
BG&E's request presented evaluations which had been made to support operation with the CEA inoperable in various axial positions as well as failing to scram when required, and proposed Technical Specification changes which would provide permission for such operation. They evaluated the effects of a range of mispositioning on the physics data used in safety and setpoint analyses. This included full-in and fJll-out mispositioning of the CEA, and where axial power distribution is of interest intermediate misalignments were examined.
Staff has reviewed BG&E's safety analyses and evaluations and agrees with BG&E's conclusion that such misalignments would not significantly affect-the data input to the safety and setpoint analysis.
The shutdown margin evaluation indicated that neither the scram function used in safety analyses nor the steam line break analysis physics input data would be.significantly affected. Simila'rly the evaluations indicated that the full-in insertion of the center CEA would'not 'ffect the physics parameters which had been used for the CEA ejection at pot analysis.
Staff has reviewed and agrees with the findings of these Bs(: evaluations.
-The calculation by the incore detector power dist ution monitoring system (INCA) would be-affected by a misalignment.
Staff agrees that these values can be appropriately adjusted by BG&E if a misalignment of the center CEA occurs.
The staff review of these evaluations by BG&E has concluded that appropriate studies and evaluations were performed by BG&E and that the results of these evaluations are reasonable in view of the low reactivity worth of the center CEA. The results of BG&E's evaluations are in agreement with staff estimates
.of the significance of possible center CEA misoperations. The staff finds that these evaluations are acceptabla. The staff expects, as has been stated by BG&E, that the center CEA will e removed from the core following Cycle 10 operation and replaced with an approved CEA.
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, 3.0 SJATENENT OF EMERGENCY CIPCUMSTANCES 3
B The February 8,1991 TWOC allowed BG&E to initially start-up as scheduled on February 9,1991. An emergency Technical Specification amendment is needed to allow BG&E to operate Unit 1 for the remainder of Cycle 10 operation due to the inoperable center CEA. During the shutdown _of the Unit on February 2,1991, the rod bottom light and lower electrical limit light, which provide indication of full insertion, did not energize when the center CEA was driven into the reactor core. Subsequent testing led to the conclusion thet the center CEA was binding in the buffer region of the guide tube due to swelling of the tips of the control rod fingers. The center CEA has been declared inoperable because of BG&E's inability to determine that it will continue to satisfy the rod drop time surveillance requirements. Because of this, the Limiting Conditions for Oseration of Technical Specification L.1.3.4 cannot be met and the plant, a)sent the TWOC, would not have been able to resume power operation.
PG&E states that the conditions leading to this situation could not have been reasonably anticipated. BGEE hed performed evaluations of observed swelling in other similar CEAs and had made correlations between observed swelling and length of operation. BG&E states that these evaluations did r.ot indicate that it was likely that the center CEA would experience any interference during Unit
- 1. Cycle 10, operation. The CEA has been fully inserted several time,e during the current cycle, and has shown no indication of interference. BG&E states that it could not have avoided this situation because the ut.
vas already operating in the current cycle when the swelling problem was discovered.
The NRC staff has reviewed BG&E's statement of emergency circumstances and concludes that BG&E has acted in good faith and that it made a timely application for revising the Technical Specifications relating to the operability and aligament of the center CEA, as detailed above. The staff further notes that BG&E will replace the center CEA with a different design during the next refueling outage which will preclude recurrence of this type of-emergency.
Based on~ the above, the Comission has determined that the licensee has not abused the emergency provisions of 10 CFR 50.91(a)(5); failure for the Comission to act on the licensee's request would result in shutdown or prevent resumption cfpoweroftheunit;andtherefore(a)herequestshouldbeprocessedunderthe t
emergency provision of 10 CFR 50.91 (5).
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SUMMARY
The staff has concluded, based on the discussions in Section 2.0, that the proposed Technical Specifications deleting the operability and alignment requirements for the. center CEA for the remainder of the Unit 1, Cycle 10, operation are acceptable.
Further, based on the discussion in Section 3.0, a determination has been made that the licensee has acted in good faith and justified the need for emergency action on SMs aandment request.
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.4 5.0 FINAL DETERMINATi0H OF NO SIGNIFICANT HAZARDS CONSIDERATION The Comission has provided standards for determining whether a significant hazardsconsiderationexists(10CFR50.92(c)). A proposed amendment to an operating license for a facility involves no significant hazards considerathn if operation of the facility in accordance with the proposed amendment woulc wt: (1) involve a significant increase in the probability or consequences o an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from an accident previously evaluated; or (5) involve a significant reduction in a margin of safety.
-The following evaluation, by BG&E and with which we agree, demonstrates that the proposed amendment does not involve a significant hazards consideration, s
[1] involve a significant increase in the probability or consequences of an sccident previously evaluated.
The Technical Specification changes will allow plant operation with the center CEA excluded from_ operability and alignment requirements.
This in itself will not affect the operation of any other CEA-or plant component.
Thus, the changes will not increase the probability of failure.of any other plant-component. Also, since the center CEA will not be operated in a different fashion than before except for possible misalignment, this change will not increase the probability of the failure of the center CSA itself. Therefore, the probability of occurrence of an accident previously evaluated is not increased.
The consequences of accidents ;treviously evaluated are not increased since, as shown in the safety analysis, none of the physics data input to the current licensing analyses for Unit 1 are invalidated due to removing the operability-and alignment requirements of the center CEA.
[2]. create possibility of a new or different type of accident from any accident previously evaluated.
The Technical Specification changes-will not affect the operation of a plant componu t other than the center CEA. The center CEA will not be operated differently than before. The misalignment of the center CEA creates new CEA configurations which have been considered,
'but it does not create new event scenarios. We[BG&E]haveevaluated the possibility that the CEA swellin assisted stress corrosion crackin. (g could induce irradiation IASCC). The cladding material in the CEA is ductile because it is a new CEA in its first Cycle 0 operation, and is not susceptible to the IASCC-related problems in high exposure CEAs, t
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involve a significant reduction in a margin of saf'ty.
I None of the physics data input to the current licensing analyses for Unit I are invalidated due to removing the o)erability and alignment requirements of the center CEA. Thus, all tie licensing analyses remain valid and the existing margin of safety is preserved.
Based on the foregoing, the Comission has concluded that the standards of 10 CFR 50.92'are satisfied. Therefore, the Comission has made a final determination that the proposed amendment does not involve a significant hazards consideration.
6.0 STATE CONSULTATION
J The appropriate representative of the State of Maryland was notified of this amendment. The State of Maryland had no coments.
7.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change in a requirement with respect to the installatinn or use of the facility components located within the restricted areas as defined in 10 CFR Part 20 and changes survillance requirements. The staff has determined that Ws amendment involves no significant increase in the aroui;tc, :.ad no sign'racant change in the types, of any effluents that may be released offsite and that there is no.-ignificant increase in individual or cumulative occupational radiation exposure. The Comission has made a final no significant hazards consideration finding with respect to this amendment.
Accordingly, this 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 this amendment.
8.0~ CONCLUSION The staff has concluded, based on the considerations discussed above, that:
(1) the amandment does not (a) significantly increase the probability or consequences of an accident previously evaluated, (b) increase the possibility of a new or different kind of accident from any previously evaluated, or (c) significantly reduce a safety margin and,)therefore, the e.mendment does no involve significant hazards consideration; (2 there is res wnAle assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Comission's regulations and the issuance of the amendment will not be inimical to the comon-defense and security nor to the health and safety of the public.
Dated:
February 20, 1991 Principal Contributors:
H. Richings D. Mcdonald