ML20212M386

Safety Evaluation Accepting Util 861223 Response to IE Bulletin 79-26, Boron Loss from BWR Control Blades, Per License Condition 2.C.(12)

ML20212M386
Person / Time
Site:	Grand Gulf
Issue date:	03/04/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20212M385	List: ML20212M381 ML20212M386
References
IEB-79-26, TAC-64235, NUDOCS 8703110418
Download: ML20212M386 (3)

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Enclosure SAFETY EVAll'ATION BY THE OFFICE OF NIICLEAR REACTOR PEGULATION RELATING TO NPF-29 OPERATING LICENSE CONDITION 2.C.(12)

SURVEILLANCE OF CONTROL BLADE (IE BULLETIN NO. (79-261 SYSTEM ENERGY RESOURCES, INC.

GRAND GULF NUCLEAR STATION (GGNS) UNIT 1 DOCKET N0. 50-416

1.0 INTRODUCTION

By letter dated December 23, 1986, System Energy Resources, Inc. (SERI) submitted its response to IE Bulletin (IEB) No. 79-26, Boron Loss from FWR Centrol Blades to satisfy NPF-29, Operating License Condition 2.C.(12).

License Condition 2.C.(12) required that a response to IEB No. 79-26 be submitted within 30 days after plant startup from the first refueling outage.

Startup after refueling began November 30, 1986.

The loss of boron carbide by leaching from cracked control blade tubino isaddressedinIEBNo.79-26and79-26 Revision 1(References 1and2)which require operating BWRs to perform various actions including (1) determining boron depletion for individual control blades, (2) limiting the maximum extent of boron depletion in individual control blades under certain conditions, and (3) conducting shutdown-margin tests and modifying shutdown margin requirements to accommodate the boron loss phenomenon. After the issuance of IE Bulletin 79-26. The General Electric Compan examinations (References 3 and and 4) ydeveloped (GE) performed a boron analysesdepletion model and post-irradiation (Reference 5). This model supports GE's claim that the amount of boron loss can be determined analytically and that potential control blade degradation resulting from this mechanism can be limited so that it will not significantly affect plant operation.

2.0 EVALUATION SERI's response to IE Bulletin 79-26 Revision 1, Baron Loss from BWR Control Blades is described as below:

Iter 1. GGNS Technical Section Instruction 09-S-02-13 " Control Rod Lifetime Calculation", requires the boron depletion of each control blade to be determined. Results from the most recent performance of this procedure (November 24,1986) indicated the highest boron-10 depletion averaged over any control blade quarter segment to be 870312043g g7ggg4 gDR ADOCK 05000416 i:

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5.71. Pecords of boron-10 depletion for each control blade are maintained on a continuing besis in-accordance with this procedure.

-Therefore, this procedure satisfies IEP No. 79-26 Revision 1, Item 1.

Item 2. The highest boron-10 depletion averaoed over any control blade-quarter segment was less than 34%. At the projected rate of boron

, depletion, no control blade was predicted to exceed the 34% limit unti! Cycle 5. Therefore, no control blades are predicted to exceed 34% boror depletion by the second refueling outage. Therefore, this satisfies IEB No. 79-26 Revision 1, Item ?.

Item 3a. GGNS Surveillance Procedure 06-RE-SB13-V-0401,_"Shutoown Margin Demonstration", was performed on November 30, 1986 during the initial startup in C Specifications (TSs)ycle 2 to satisfy this item and GGNS TechnicalSurveilla This surveillance test involved pulling control rods in a nomal startup sequence under cold xenon-free core conditions until criticality with a slightly positive reactor period was cbtained.

The control rod pattern was recorded along with the reactor coolant temperature and the reactor period. The reactivity associated with the critical control rod pattern was corrected to compensate for the reactivity worth of the positive period and the reactivity worth of the increased reactor coolant temperature above the 68' F analytical temperature.

The Cycle 2 minimum shutdown margin was calculated by subtracting the reactivity of the analytically detemined highest worth rod and the R factor from the temperature and period corrected reactivity cf the critical control blade pattern. The R factor accounted for the difference in shutdown margin at beginning of cycle and the shutdown margin at the most reactive point during the cycle. GGNS Surveillance Procedure 06-RE-SB13-V-0401 performed on November 30, 1986 determined the cycle minimum shutdown mergin to be 2.75% dK/K, which satisfied the GGNS Technical Specifications 3.1.1.a Limiting Condition for Operation to maintain a shutdown margin of at least 0.38% dK/K. Therefore, this surveillance test satisfies the require-ment of IEP No. 79-26 Revision 1. Item 3a.

Item 3b. GGNS Technical Section Instruction 09-S-02-13. " Control Rod Lifetime Calculation", was most recently performed on November 24, 1986 to determine the current boron depletion for every control blade. The procedure performed on Novertber 24, 1986 prior to startup in Cycle 2.

determined the hiahest boron-10 depletion averaged over any quarter segment of any control blade to be 5.70% and estimated that the end of control rod blade lifetime limit of 34% average boron-10 depletion in any quarter seament would not be reached until Cycle

5. This 34% lifetime limit includes loss of boron poison due to cracking of the absorber rod tubes in addition to the boron

depletion factor. Grand Gulf procedures require a control bl6de to be replaced prior to the cycle in which t_he estimated boron-10 depletion for any quarter segment exceeds 34%, thus ensuring that the shutdown margin determinaticn is not adversely impacted by the boron loss phenomenon. The low control blade depletion at the end of Cycle 1 and the procedural controls to replace control red blades prior to exceeding 34% depletion satisfies the requirement of IEB No. 79-26 Revision 1. Item 3b.

3.0 CONCLUSION

The staff has reviewed SERI's letter dated December 23, 1986, which was submitted in response to NPF-29 Operating License Condition 2.C.(12). Based on its review, the staff concludes that the SERI submittal meets the guidelines of IE Bulletin 79-26 Revision 1, " Boron Loss from BWR Control Blades" and satisfies the time requirement for submittal in NPF-29 Operating License Condition 2.C.(12) and, therefore, is acceptable.

4.0 REFERENCES

-1. IE Bulletin No. 79-26, " Boron Loss from BWR Control Blades, " dated November 20, 1979 US NRC, Washington, D.C.

'2. IE Bulletin No. 79-26 Revision 1 " Boron loss from BWR Control Blades,"

dated August 29, 1980, US NRC, Washington, D.C.

3. K. W. Brayman and K. W. Cook, " Evaluation of Control Blade Lifetime With Potential loss of B C", NEDE-24226-P, Class III, December 1979, Nuclear A

Power Systems Division, General Electric Company, San Jose, CA.

4 K. W. Brayman, P. vanDieman, K. M. Douglas and L. M. Zull, " Evaluation of Control Blade Lifetime With Potential Less of 8 4C (Supplement li."

NEDE-24226-1, Class III, March 1981 Supplement 1, Nuclear Power Systems Division, General Electric Company, San Jose, CA.

5. K. W. Brayman, K. M. Douglas, P. vanDieman, and L. M. Zull, " Control Blade Examination Results and Response to Item 4 of Bulletin 79-26,"

NEDE-24325-P Class III, March 1981, Nuclear Power Systems Division, General Electric Ccmpany, Sen Jose, CA.