Part 21 Report - 1998-183
ACCESSION #: 9806100377
Consumers Energy
A CMS Energy Company
Palisades Nuclear Plant Tel. 616 764 2276
27780 Blue Star Memorial Highway Fax: 616 764 2490
Covert, MI 49043
Nathan L. Haskell
Director, Licensing
June 1, 1998
U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk
Washington, DC 20555
DOCKET 50-255 - LICENSE DPR-20 - PALISADES PLANT
EVALUATION OF 10 CFR PART 21 REPORT REGARDING IMPACT OF RELAP4
EXCESSIVE VARIABILITY ON PALISADES LARGE BREAK LOCA ECCS RESULTS
In accordance with 10 CFR 50.46(a)(3)(ii), a report is required to be
submitted within 30 days of discovery of a significant change or error in
an Emergency Core Cooling (ECCS) analysis. The purpose of this letter is
to report a significant change in the calculated peak cladding
temperature (PCT) values as a result of an error in the Palisades large
break loss of coolant accident (LBLOCA) ECCS evaluation model.
On January 15, 1998, per 10 CFR Part 21, the NRC was informed of a
deviation in the Seimans Power Corporation (SPC) EXEM/PWR LBLOCA
evaluation model related to RELAP4 excessive variability. During a
presentation to the NRC on March 10, 1998, Palisades agreed to report the
results of the evaluation of this deviation based on the corrected model
for both fuel Cycles 13 and 14. That report is provided in the
attachment.
Based on the currently approved and the corrected LBLOCA evaluation
model, the change in the PCT during Cycle 14 from that during Cycle 13 is
not significant. However, the evaluation of the corrected model has
shown that a significant (per 10 CFR 50.46) change in the PCT values for
both fuel Cycles 13 and 14 will result from the error correction.
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SUMMARY OF COMMITMENTS
This letter contains no new commitments and no revisions to existing
commitments.
Nathan L. Haskell
Director, Licensing
CC Administrator, Region III, USNRC
Project Manager, NRR, USNRC
NRC Resident Inspector - Palisades
Attachment
ATTACHMENT
CONSUMERS ENERGY COMPANY
PALISADES PLANT
DOCKET 50-255
EVALUATION OF 10 CFR PART 21 REPORT REGARDING IMPACT OF RELAP4
EXCESSIVE VARIABILITY ON PALISADES LARGE BREAK LOCA ECCS RESULTS
3 Pages
EVALUATION OF 10 CFR PART 21 REPORT REGARDING IMPACT OF RELAP4
EXCESSIVE VARIABILITY ON PALISADES LARGE BREAK LOCA ECCS RESULTS
REFERENCES
1. Letter, JSHolm (SPC) to Document Control Desk (NRC), "Interim Report
of Evaluation of a Deviation Pursuant to 10 CFR 21.21 (a)(2)",
NRC:98:001, January 15, 1998.
2. Letter, JFMallay (SPC) to Document Control Desk (NRC), "RELAP4
Excessive Variability", NRC:98:016, March 17, 1998.
3. Letter, JFMallay (SPC) to Document Control Desk (NRC), "Interim
Report of Evaluation of a Deviation Pursuant to 10 CFR 21.21
(a)(2)", NRC:98:020, April 1, 1998.
4. Letter, JFMallay (SPC) to Document Control Desk (NRC), 10 CFR Part
21 evaluation and Notification for RELAP4 Excessive Variability",
NRC:98:026, May 1, 1998.
5. Letter, TCBordine (Consumers Energy) to Document Control Desk (NRC),
"Notification Under 10 CFR 50.46 of Change in ECCS Calculation
Results", dated April 30, 1997.
6. Letter, TCBordine (Consumers Energy) to Document Control Desk (NRC),
"Annual Report of Changes in ECCS Models per 10CFR50.46", dated
November 26, 1997.
BACKGROUND
In a letter dated January 15, 1998, NRC was informed of a deviation in
the SPC EXEM/PWR LBLOCA evaluation model related to RELAP4 excessive
variability (Reference 1). The nature of the deviation was that small
changes in the input to RELAP4 can result in large changes in the
calculated peak cladding temperature during a LBLOCA. At that time, SPC
informed Consumers Energy that there was no indication that the RELAP4
excessive variability problem, after correction, would result in a PCT
that would violate 10 CFR 50.46 limits for the Palisades LBLOCA analysis.
On March 10, 1998, SPC made a presentation to the NRC regarding the
status of the RELAP4 excessive variability evaluation. In response to a
request by NRC, SPC provided a summary of the meeting presentation and
documented the future actions proposed (Reference 2). It was agreed that
SPC would continue to use the currently approved EXEM/PWR LBLOCA model,
modified by the interim fuel cooling testing facility (FCTF) correlation,
to perform plant analyses in the near term. In the longer term, SPC
would correct the current model for excessive variability and submit a
topical
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EVALUATION OF 10 CFR PART 21 REPORT REGARDING IMPACT OF RELAP4
EXCESSIVE VARIABILITY ON PALISADES LARGE BREAK LOCA ECCS RESULTS
report to NRC for review. Additionally, in an effort to ensure that
Palisades LBLOCA calculations based on the current RELAP4 model continue
to be conservative with respect to the excessive variability, SPC agreed
to perform confirmatory calculations with a corrected model for
comparison purposes. Palisades agreed to report the results of the 10
CFR Part 21 evaluation based on the corrected model for both fuel Cycles
13 and 14.
A modification to the original (Reference 1) 10 CFR Part 21 evaluation
schedule was transmitted to NRC by SPC on April 1, 1998, (Reference 3),
indicating that the evaluation would be completed on May 1, 1998, rather
than April 3, 1998. In a letter dated May 1, 1998, (Reference 4), SPC
transmitted the results of their 10 CFR Part 21 evaluation. A summary of
the evaluation results, with respect to the Palisades LBLOCA analyses
follows.
IMPACT OF RELAP4 EXCESSIVE VARIABILITY ON PALISADES CYCLE 13 LBLOCA
ANALYSIS
In letters dated April 30, 1997, and November 26, 1997, (References 5 &
6), Consumers Energy reported that the PCT predicted by the LBLOCA
analysis for fuel Cycle 13 was 1892 Degrees F. The Cycle 13 analysis and
resultant PCT were based on the currently approved SPC RELAP4 LBLOCA
model. The results of confirmatory calculations indicate that when the
RELAP4 model is corrected for excessive variability, the predicted PCT
will be lower by about 113 Degrees F. Therefore, the deviation
identified in Reference 1 and further identified as a reportable error in
Reference 4 is significant per 10 CFR 50.46. This deviation is
considered conservative for the Palisades Cycle 13 LBLOCA analysis.
IMPACT OF RELAP4 EXCESSIVE VARIABILITY ON PALISADES CYCLE 14 LBLOCA
ANALYSIS
Re-analysis of the LBLOCA event based on the current RELAP4 model has
recently been completed by SPC for Palisades fuel Cycle 14, resulting in
a PCT of 1869 Degrees F. This result constitutes a 23 Degrees F drop in
calculated PCT from fuel cycle 13 to fuel cycle 14. The change in PCT
between Cycle 13 and Cycle 14 was due primarily to revised core fuel
design (pellet diameter and clad thickness) and neutronics values (radial
peaking factors) which were used to reflect the Cycle 14 core design and
reload "R" fuel. The change in PCT between Cycle 13 and Cycle 14 does
not constitute a significant change per 10 CFR 50.46.
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EVALUATION OF 10 CFR PART 21 REPORT REGARDING IMPACT OF RELAP4
EXCESSIVE VARIABILITY ON PALISADES LARGE BREAK LOCA ECCS RESULTS
The results of confirmatory calculations for Cycle 14 indicate that when
the RELAP4 model is corrected for excessive variability, the predicted
PCT will be lower by about 70 Degrees F. Therefore, the deviation
identified in Reference 1 and further identified as a reportable error in
Reference 4 is significant per 10 CFR 50.46. This deviation is
considered conservative for the Palisades Cycle 14 LBLOCA analysis.
CONCLUSION
The Palisades Cycle 13 and 14 LBLOCA analyses demonstrate that the
acceptance criteria of 10 CFR 50.46 continue to be satisfied based on
calculations performed with both the currently approved EXEM/PWR LBLOCA
model, modified by the interim FCTF correlation, and the EXEM/PWR LBLOCA
model corrected for excessive variability. Confirmatory calculations
performed indicate that PCT will drop by greater than 50 Degrees F when
the current model is corrected for excessive variability, which
constitutes a significant change per 10 CFR 50.46. However, the
resulting changes in the PCT for fuel Cycles 13 and 14 will be in the
conservative direction.
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