ML20128B318

Discusses Review of Insp Rept 050-263/73-05 Re Prediction of Critical Rod Positions in Error by Large Margin & Requests That Rept from Util Be Provided on Error

ML20128B318
Person / Time
Site:	Monticello
Issue date:	07/23/1973
From:	James Keppler US ATOMIC ENERGY COMMISSION (AEC)
To:	Jennifer Davis US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20128B252	List: ML20128B250 ML20128B318
References
NUDOCS 9212030626
Download: ML20128B318 (2)

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f v UNITED STATES I - s 5 ATOMIC ENERGY COMMISSION l 'l b l' '

WASW NGTON, D.C. 205 0

%, 7 JUl. 2 3 1973

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J. G. Davis, Deputy Director for Field Operations CRITICALITY PREDICTION ERROR AT MONTICELLO Our review of Monticello Inspection Report No. 050-263/73-05 disclosed that NSP has experienced another situation where the prediction of critical rod positions was in error by a large margin (predicted criti-cality-31 rods withdrawn, actual criticality-15 rods withdrawn). An earlier error in prediction of critical rod positions occurred in January 1972 (predicted 43, actual 23) and this was the subject of NSP reports to DL dated February 3 and 29, 1972. These reports disclosed that information presented in the FSAR on reactivity predictions and shutdown margin was in error and needed to be corrected for Monticello and special tests were required at Monticello to verify shutdown margin.

Subsequently, revised shutdown margin curves were also provided for other BWR's. The reports to DL also disclosed that methods used to predict criticality were inadequate and, as a result, a new core analysis program was developed by NSP to improve core reactivity prediction capabilities at Monticello.

Based on our review of the information in the inspection report on l the most recent incorrect prediction, it appears that either the core

( analysis program developed by NSP in early 1972 was not adequate to l prevent recurrence or that there may be other unknown factors on core performance responsible Ior the anomaly. Furthermore, we do not believe that the Region has placed the proper emphasis on this matter in view of

, the fact that this problem was not promptly identified to Headquarters, l vas not highlighted in the summary section of the inspection report, and NSP was not cited for failure to submit a report to DL in accordance l

l with the Technical Specifications.

l In view of the potential safety considerations, we believe you should notify the Region to request NSP to submit a report to DL on this matter.

In our view, the report should conta1n the following information:

1. A discussion of the factors responsible for the error in prediction and the corrective actions taken to prevent recurrence.

2. Deficiencies identified ir, the core analysis program as a result of the recent prediction error.

9212030626 720802 PDR ADOCK 05000263 G PDR .

.' - t 4 J. G. Davis JUL 2 3 573 -

3. The effects of any deficiencies identified in the core analysis program and related computer codes on normal operation, transient *'

and accident analysis, and shutdown margin for Monticello.

2 This matter has been discussed with the DL project manager and he is in agreement both .with the need for a report and the content of the~ report.

If you have any questions concerning-this matter, please let me know.

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(J. G. Keppler, Acting Assistant Director for Construction and' Operatic-s Directorate of. Regulatory Operations cc: D. F. Knuth, R0 H. D. Thornburg,-RO G. W. Reinmuth, RO t

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