ML20150D555

Safety Evaluation Accepting Extended Burnup of Batches K & L for Facility,Per ANF-87-139, Extended Burnup Rept for Fort Calhoun Reloads XN-4 & XN-5 (Batches K & L)

ML20150D555
Person / Time
Site:	Fort Calhoun
Issue date:	03/11/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20150D551	List: ML20150D548 ML20150D555
References
NUDOCS 8803240342
Download: ML20150D555 (3)

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ENCLOSUDE 1 SAFETY EVALUATION BY THE OFFICE OF Nt! CLEAR REACTOR REGillATION TOPICAL PEPORT ANF-87-139(Pj d V. O "EXTFNDED BURNUP RFPORT FOR FORT CALHOUN RELOADS XN-4 AND XN-5 (BATCHES K AND L)"

OMAHA PUBLIC POWER DISTRICT FORT CALH0llN DOCKET NO. 50-?85

1.0 INTRODUCTION

By a letter dated December 14, 1987, from R. L. Andrews (OPPD) to NRC, the licensee submitted a topical report entitled "Extended Burnup Report for Fort Calhoun Reloads XN a and XN-5 (Batches X and L)" (ANF-87-130), for Fort Calhoun. The report describes fuel assembly design for extended burnup based on the approved generic topical report XH-NF-82-06, Rev. 1 (Qualification of ANF Fuel for Fxtended Burnup Peportl. However, there are a few conditions attached to the approval of XN-NF-8?-06, which should be addressed by each licensee referencing the generic report.

The Fort Calhoun fuel assembly is a 14x14 array, consisting of 176 fuel rods, 5 guide tubes, and 9 bi-metallic grid spacers. The XN-4 and XN-5 fuel assemblies are designed to reach high burnup ranges of 49,000 and 51,600 mwd /MTU peak rod burnup, respectively.

Our review and evaluation address only those items listed in the safety evaluation of the generic report XN-NF-92-06, Rev. I with respect to Fort 1 Calhoun fuel for extended burnup.

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2.0 EVAttlATION (1) Ciadding Design Strain The design criterion for fuel rod cladding strain is that the total mean circumferential strain shall not exceed 1% for steady-state conditions and anticipated operational occurrences. We have approved this cladding design strain criterion in the generic report XN-NF-82-06, Rey, 1.

The licensee performed the cladding strain calculation usino the approved fuel performance code PODEX2 and six different bounding power histories. The results showed that the predicted strains were well below 1% limit. We thus conclude that the licensee has demonstrated an acceptable strain calculatinn and Fort Calhoun fuel rods will remain below 1% limit.

(2) Strain Fatigue The design criterion for fuel rod cladding fatigue is that the cumulative fatigue usage factor be less than 0.67 when a minimum safety factor of ? on the stress amplitude or a minimum safety factor of 20 on the number of cycles is imposed as defined by the O'Donnell and Langer fatigue curve. This criterion is consistent with SRP and is thus acceptable.

The licensee performed the fatigue analysis using a transient code RAMPEX to conservatively predict stress levels. Six different power histories were used. The results showed that all cumulative fatigue usages were below 0.67.

We thus conclude that there is reasonable assurance that strain fatigue will  :

not be a problem for Fort Calhoun.

(3) Rod Internal Pressure The approved rod internal pressure criterion in the generic report XN-NF-82-06, Rev. 1 is that the end-of-life rod pressure shall not exceed a I

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3 certain limit above the system pressure. This limit is a proprietary value, and we have accepted this proprietary value. Hence, the rod pressure criterion is acceptable for Fort Calhoun.

Based on the approved code R0DEX2 and conservative power histories, the licensee calculation showed that the rod internal pressures remained below system pressure for all power histories.

We thus, conclude that there is reasonable assurance that the rod pressure will not be a problem for Fort Calhoun.

(4) Creep Collapse The creep collapse design criterion is that the cladding creep collapse is precluded during the fuel rod lifetime. We have approved the creep collapse calculational model in XN-NF-82-06, Rev. 1. The approved model indicates that creep collapse results when fuel pellet hangup occurs, followed by the formation of an axial gap in the fuel stack due to fuel densification early in life. Based on the approved method, the licensee determined that there were no pellet hangups due to cladding creepdown early in life, thereby the cladding collapse was prevented through its lifetime. We agree with the licensee's assessment. Therefore, the creep collapse will not be a problem in Fort Calhoun.

3.0 CONCLIISION We have reviewed the licensee's submittal (ANF-87-139) for Fort Calhoun fuel for extended burnup. Based on the approved generic topical report XN-NF-82-06, Rev. I and plant-specific results, we conclude that the topical report ANF-87-139 is acceptable for extended burnup licensing applications for Fort Calhoun, and the XN-4 and XN-5 fuel assemblies are approved for extended burnups up to'49,000 and 51,600 PWd/MTil, respectively, f