ML20101G921

Part 21 Rept Re Rotated Fuel Assemblies Sometimes Inappropriate for Modern Type Fuel Designs.Reevaluation Concluded That Inadvertently Rotated Fuel Assembly for BWR 4/5 C-lattice Plant Could Not Exceed TS Safety Limit MCPR

ML20101G921
Person / Time
Site:	Perry, Grand Gulf, River Bend
Issue date:	06/19/1992
From:	Stark S GENERAL ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-92 MFN-132-92, PWM-92-056, PWM-92-56, NUDOCS 9206290026
Download: ML20101G921 (4)

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GE Nuclear e netuv June 19,1992 92 01nre.wp PWS192 056 51FN# 132-92 Document Control Desk U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

10Cl R PART 21, Ill:POllTAllt.E CONDITION 1(utated C- or S-l. attire 1 uel Assemhi)

This letter is to inhum the NRC of a repoitable detect per 10CFR Part 21. as reported to Thomas H.

Andrews. the duty otticer in the NRC operations center by G.11. Strambael, Safety 1: valuation Programs hianager on June 19. 1992.

Recent studies have shown that the coaelusion of a generie analysis performed in 1982, regarding rotated tuel assemblies, is sometimes inappropriate for modern type fuel designs. Even though a substantial sately hazard does not exist, this issue is reportable to the NRC because of the potential for exceeding the Technical Specification Safety 1.imit NICPR.

The af fected flWR plants are neing nontied of this condition The attached reportable condition report identities all pertinent information required by 10Cl R Part 21.

Very truly yours, e <

C ,

D,d. b-S. J. Stark, Acting hianager Regulatory and Analysh Services Attachment ee: R. C. Jones. NRC-Rockville C. E. Rossi, NRC-Rockville L. S. Gittord. GE-Rockville e

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Attachment l

REPORTABLE CONDITION i (i) Name und address of the indhidual or individuals informing the Commission. j

, S. J. Stark, Acting Manager of Regulatory and Analysis Services, GE Nuclear Energy,175 Curtner Avenue, San Jose, CA 95125 (11) Identification of the facility, the activity, or the basic component supplied for such facility or such utthily within the United States which fails to comply or contains defect.

llackground The concern is the change in Critical Power Ratio (CPR) resulting from the inadvertent rotation of a fuel assembly in a C- or S lattice plant. The original approved version of GESTAR-II (NEDE 24011 P A, Rev. 0) concluded that there is no need to perform cycle specific evaluations of a rotated fuel assembly for a C-lattice plant since the change in CPR was analyzed ,

to be insignificant due to the fuel design configuration. The original generic studies performed i in 1982 had shown that this change in CPR was approximately 0.07 and, therefore, could never '

impact the plant Technical Specification (Tech Spec) Safety Limit Minimum Critical Power I Ratio (MCPR).

The rotation of the C- or S-lattice fuel assembly is important because the physical configuration of the fuel assembly and its mating surfaces has a symmetric configuration with the fuellower easting, however, the fuel assembly mating at the upper core plate is not symmetric. When rotated, there is a slight vertical tilt of the fuel assembly from the bottom to the top of the fuel assembly. This vertical tilt results in a non-uniform water gap over the active fuel length. This non-uniform water gap changes the local power peaking of the fuel rods, thereby changing the CpR of the fuel assembly.

The 1982 generic analysis included the variable water gap of a rotated bundle. Recent studies have now shown that the conclusion of the generic analysis is sometimes inappropriate for modern type fuel designs. This conclusion is different because of the evolution cf the fuel designs and their nuclear characteristics, not the calculation procedures employed.

(iii) IdentificMion of the firm constructing the facility or supplying the basic component which falls to comply or contains a defect.

GE Nuclear Energy, San Jose, California.

(iv) Nature of the defect or failure to comply and the safety hazard which is created or could he created by such defect or failure to comply. ,

Safety liasis-

- GE performed a complete re-evaluation of the CPR impact of a rotated fuel assembly in C and S lattice plants, includirag calculating the magnitude of the fuel assembly tilt, the impact on local power peaking, the impact on R-factor and the resulting delta CPR. This evaluation included thc NRC mandated 1.01 multiplier to rotated bundle R-factors and the 0.02 delta CPR adder to the final calculated value cthe delta CPR.

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Attu b nent (cont'd) r The re-evaluation concluded that:

1) An inadvertently rotated fuel assembly for a BWR 4/5 C-lattice plant could not have resulted in exc, eding the Tech Spee Safety Limit MCPR.

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2) For BWR/6 S-lattice plants the delta CPR for the rotated bundle is larger than the delta CPR calculated for the identified limiting transient.

A) Review of the exposure accounting for a BWR/6 plant during a past operating cycle i revealed that the Tech Spec Safety Limit MCPR for this BWR/6 S-lattice plant could not j have beto exceeded with an inadvertently rotated fuel assembly.

i B) Assum:ng that a BWR/6 S-lattice plant is operanng at the Operating Limit MCPR, i

this postulated rotated bundle condition could result in exceeding the Tech Spec Safety Limit MCPR. Even though a substantial safety hazard does not exist, this issue is reportable to the NRC because of the potential for exceeding the Tech Spec Safety Limit

• MCPR.

In the late 1970's the NRC mandated that either the calculated delta CPR for a rotated bundle has to be added to the Safety Limit MCPR, or appropriate Tech Spec limits must be adopted to assure detection of the postulated fuel _ failures resulting from a rotated bundle and appropriate .

action taken. It continues to be the GE posHon that the rotated bundle she.nld be considered as an accident and demonstrated compliance to an MCPR Safety Limit is not required.

Furthermore, it is important to note that there has been no identified instance of a plant being

operated with a rotated bundle since the 1980 issuance of GE Service laformation Letter (SIL)  ;

347 "Misuriented Fuel Bundles" i

e (v) The date on which the information of such defect or failure to comply was obtained, i

June 17,1992 (vi) In the case of a 1,asic component which contains a defect or falls to comply, the number and

, location of all such components in use at, supplied for, or being supplied for one or more facilities or activities subject to the regulations in this part.

i l Clinton, Grand Gulf, Perry, River Bend. and plants outside the United States.

I j (vii) The corrective action which has been, is being, or will be taken; the name of the individual or -

l organization responsible for the action; and the length of time that has been or will be taken to

complete the action.

l All BWR/6 utilities were informed of the on-going evaluation. Cycle specific delta CPR values accounting for the rotated bundle event have been calculated and provided to the near term operating BWR/6s with GE fuel. The NRC was informally contacted. GE has scheduled a meeting with the NRC staff to re visit the rotated bundle analysis design basis with the intent to request removal of the requirement to apply transient event acceptance criteria. GE will perform cycle specitic rotated bundle analyses for future C- and S-lattice fuel designs until the j NRC agrees with redefinition of the acceptance criteria. GESTAR-Il will be appropriately 2

revised. GE will inform all BWR utilities of this issue because it emphasizes the significance of i maintaining sound core verification techniques.

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, . Atturhinent (cont'd)

(sili).- Any adsice related to the defect or failure to cornply about'the facility, activity, or basic curuponent that has been, is being, or will be gisen to purchasers or licensees.

See vil above.

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