ML20041F977
| ML20041F977 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 03/11/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20041F971 | List: |
| References | |
| NUDOCS 8203170612 | |
| Download: ML20041F977 (4) | |
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UNITED STATES
[1p.qyj NUCLEAR REGULATORY COMMISSION MC WASHINGTON. D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 28 TO PROVISIONAL OPERATING LICENSE NO. DPR-45
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DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR DOCKET NO. 50 409 1,0 INTRODUCTION By letter dated February 23, 1982, as supplemented by letter dated March 4, 19S2, DLiryland Fower Cooperative (DPC) (the licensee),
proposed changes to Appendix A of the Technical Specifications for the La Crosse Boiling Water Reactor (LACBWR). The changes involve
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revision to fuel exposure (burnup) limitations for fuel assemblies not located on the periphery of the core for Cycle 7.
2.0 BACKGROUND
The La Crosse Boiling Water Reactor (LACBWR), owned and operated by the Dairyland Power Cooperative (DPC) in Wisconsin, is a 165 megawatt (thermal) plant, built by Allis Chalmers.
It is the only Eoiling Water Reactor that utilizes fuei rods with stainlass steel cladding, and it has had a history of fuel failure problems associated with stress corrosion cracking (SCC) of the ;'ainless steel.
For example, as many as 26 of 72 fuel assemblies ccnstituting the LACEWR core were founc to have some degree of fuel damage, including leaking rods and nissing sections of rods (57 inches in ene case),
at the end of Cycle 4 (refs. 1, 2).
As a result of a lengthy and ccmp ehensive study of the contributing factors to the failures, a technical specification on fuel assembly burnup (No. 4.2.4.2.5) was imposed in March 1978 as part of Amendment 11 to the license. The burnup limitation was 15,000 MWD /MTU on all assemblies in the core.
Subsequently, the maximum allowable average exposure linit (cf any fuel assembly) was raised to 15,600 i%D/MTU. To compcasate for this i crease in naximum allowable excesure, new and more restrictive limits n
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It Arend-ment 20 (Ref. 4), the burnup limitation was removed from fuel assemblies located on the per'iphery of the core in recognition of fact that operating eroerier cs had shoven that the 2E outer fcel assenblies had hSd a much lower rate of f ailure than the 44 interior fuel assemblies. This trend has been attributed to the lower power density along with reduced effects of control rod movements at the peripheral locations. Amendment 26 (Ref. 6) to the LACEWR license was issued on November 6,1981 in response to a June 1,1981 recuest (Ref. 5) from LACEWR.
Because of the much improved Cycle 7 performance of the LACEWR fuel (shown by low off-gas and primary coolant activity), the burnup limit for fuel assemblies not located on the perichery of the core was increased f_ rom 15,600 MWD /MTU to 16,500 MWD /MTU.
8203170612 820311 PDR ADOCK 05000409 P
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L 3.0 DISCUSSION AND EVALUATION
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The proposed technical specification (Ref. 7) would further increaseallowable exposure of LACBWR fuel (Technical Specification 4.2.4.2.5) from 16,300 MWD /MTV to 17,200 MWD /MTV. The licensee's main rationale. for the requested burnup extension is the apparent improved performance of the redesigned Type III (Exxon) fuel that now constitutes all but two of the assemblies in core.
According to DPC the improved performance (relative to Cycle 1 through 5 experience with Allis/Chalmers fuel) is being demonstrated by off-gas and primary coolant gross e/V, a, I-131 and Dose Equivalent I-131 activities that are less than or approximately equal to those exhibited during the previous cycle of operation (Cycle 6).
At the end of Cycle 6, the assev61ies with more than one cycle of operation were examined visually and by dry sipping, cod only one " probable" leaker was found.
In their February 23,.1982 submittal (letter, Frank Linder to Dennis Crutchfield), DPC provided the following correlation that can be.used' to estimate the number of failed fuel rods from the off-gas activity rate.
R
= 0.096 (0G (P /P) - 356,)
def p
where R ef is the number of defective rods in the core, 0G is the off-gas d
activity (Cj/ day) and P /P is the rated thermal power to operation F
thermal power ratio. This relation was fitted to EOC5 and 6 da.ta by DPC and reportedly " predicts" the conditions observed at E0C 1A, 2, and 3 quite well. When applied to the present operating conditions, DPC states that the correlation indicates there is at most about six or seven failed fuel rods in the LACEWR core. That is considered to be a conservative estinate, since DPC's "best estimete" Lased en previous experience is that tnere is currently only one failed rod (Ref. 8).
In addition to providing a failed fuel correlation end current estimate of the number of failures based on off-gas activity, DPC has also reaffirmed their ccmmitment to (a) closely monitor the off-gas activity and to provide estirates cf any increase in fuel failures, and (b) examine all the fuei asse-t'ies 'n the prcscnt c:ra : ttc n;xt rtfucling cutage, t:th /isually and by dry sipping, to confirm the integrity of the assemblies and to identify the location of suspected leakers.
DPC has also proposed to place a more corservative limit in Technical Soecification d.2.2.22 for off-gas activity.
Tae new limit will be 571 Ci/ day for the limited extension of Cycle 7 operation (versus the present 750 Ci/ day). As a point of reference, the peak activity reading in late February 1982 was 387 Ci/ day.
If the off-gas activity were to further increase s'ignificantly above current daily values, we would expect DPC to take appropriate mitigating actions, including possibly reducing reactor power.
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Therefore, on the basis of the reported generally improved (relative to Cycles 1 tnrough 5) performance of the Type III Exxon. fuel and the commitment to (a) continue fuel failure monitoring, (b) perform visual ~and sipping examinations at the next refueling outage, and (c) reduce the off-gas activity limit for the remainder of Cycle 7 operation, we conclude that reasonable assurance has been provided that the proposed burnup extension will not endanger the health and safety of the public and that the burnup extension should be approved for the remainder of Cycle 7 operation.
Because LACBWR has had a history of cladding problems related to stress corrosion cracking, we believe that a permanent extension to the burnup limit should await confirmation of satisfactory performance.
Such con-firmation may be provided by the post-irradiation examinations to be performed at the next refueling outage.
Thus, we find the proposed change, as modified, acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
We have determined that this amendment does not autnorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this.
determination, we have further concluded that the amendment-involves an-i action which is insignificant from the standpoint of environmental impact and, pursusnt to 10 CF 551.5(d)(4), that an environmental impact statement, i
or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
5.0 CONCLUSION
We have concluded, based on the consideration discussed above, that:
(1) because the amend ent does not involve a significant increase in the. pro-bacility or consecuences of accidents previcusly considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not endangered by operation in the proposed manner, and (3) such activities will be conducted in comDliance with the Commission's regulations and the issuance of the amenenent will not be inimical to the common defense and security or to 4 21 u c c
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4 6.0 ACKNOWLEDGEMENTS The following NRC pertornei have contributed to this evaluation:
M. Tokar R. Dudley Date:
March 11, 19E2
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REFERENCES 1.-
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R~. Riggs, " Analysis lof LACBWR Fuel Failures," USNRC, February 1978, attachment to Amendment 11 to Operating License No. DPR-45, March 3, 1978.
- 2. _ Paul S. Check (NRC), Memorandum to Dennis L. Ziemann, " Motion to Suspend DPR-45 (LACBWR) License (TAC 11839), July 19, 1978.
3.
Dennis L. Ziemann (NRC) Letter to Frank Linder (DPC), with Amendment _19 to License No. DPR-45, February 4, 1980.
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4.
Dennis M. Crutchfield -(NRC), letter -to Frank Linder (DPC), with Amendment 20 to License no. DPR-45,11ay 13,1980.
Sa. Frank Linder (DPC) Letter to Dennis M. Crutchfield, (NPC), No. LAC-7572, June 1, 1951.
- b. S. J. Rafferty, "LACBWR Cycle 5 Fuel Performance and Finalized Refueling Plan for Cycle 7," Enclosure 1 to DPC letter LAC-7572, DPC Report LAC-TR-096 (Undated) 6.
Dennis'ft. Crutchfield (NRC), Letter to. Frank _Linder DPC), with Amendment 24 to License No. DPR-45, November 6, 1981.
7.
Frank Linder (DPC), Letter to Dennis M. Crutchfield (URC), No. LAC-8109, February 23, 1982.
8.
Frank Linder (DPC, Letter to Dennis M.-Crutchfield, (NRC).fh). LAC-9131, March 4, 1982.
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