Part 21 Report - 1998-410
ACCESSION #: 9805190348
May 11, 1998
Document Control Desk
ATTN: Chief, Planning, Program and Management Support Branch
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555-0001
Interim Report of Evaluation of a Deviation Pursuant to 10 CFR
The following information is provided pursuant to the requirements of 10
CFR 21 to submit an interim report on issues that will not be completed
within 60 days of discovery.
An interim report for an issue under evaluation by Siemens Power
Corporation is enclosed:
Interim Report No. 98-003 "Steam Line Break"
Those SPC customers potentially impacted by this issue will be provided a
copy of this interim report.
If you have any questions or if I can be of further assistance, please
call me at (509)375-8757.
Very truly yours,
James F. Mallay, Director
cc: Mr. E. Y. Wang (USNRC)
Project No. 702
Siemens Power Corporation
Nuclear Division 2101 Horn Rapids Road Tel: (509) 375 8100
Engineering & P.O. Box 130 Fax: (509) 375 8402
Manufacturing Richland, WA 99352-0130
Interim Report (98-003)
Interim report of evaluation of a deviation. pursuant to 10 CFR
Steam Line Break
Identification of Basic Activity:
PWR Steam Line Break Analysis
Basic Activity Supplied by:
Siemens Power Corporation - Nuclear Division
Nature of Deviation:
Three deviations have been identified that are applicable to either the
SPC Steam Line Break methodology or its application to individual plants.
The first deviation is that power distributions which may not bound
potential plant conditions during a Steam Line Break event have been
identified in the Steam Line Break analyses for some plants. The
inadequate determination of power distributions results from the
1. variations in cycle to cycle radial peaking factors due to loading
pattern changes which were not accounted for in the Steam Line Break
2. the iteration technique between the XCOBRA-IIIC thermal hydraulic
code and the XTGPWR neutronics code may not ensure that a
conservative power distribution is calculated for cases where the
pumps are turned off.
A second deviation is that the iteration between XCOBRA-IIIC and XTGPWR
may result in non-conservative reactivity calculations with XTGPWR. This
is a deviation in the SPC Steam Line Break methodology.
A third deviation is that the reactivity control system input for the
ANF-RELAP HFP analyses were constructed for some plants such that a step
change occurs in the Doppler reactivity when switching between two
reactivity models. This deviation results in an under prediction of the
positive reactivity insertion due to the cool down of the fuel during the
Steam Line Break event.
An evaluation of whether these deviations represent reportable defects
under 10 CFR 21 has been initiated. A schedule for completing the
evaluation is provided below.
March 13, 1998
Corrective Actions to Date:
Condition Report (CR) 6571 was initiated on March 13, 1998 and CR 6599 on
March 21, 1998.
A self-assessment is being performed to assess the deviations identified
in the condition reports and any other issues which may be identified by
a review of the Steam Line Break methodology. A set of recommendations
from the self-assessment team will be issued during May. It is apparent
from the initial self-assessment team findings that a change in the
approved Steam Line Break methodology will be necessary to correct the
identified deviation with respect to the iteration between XCOBRA-IIIC
An evaluation of the impact of the combined effects has been made for two
representative plants. The evaluations indicate that no significant
increase in fuel rod failures is expected from the correction of the
identified deviations. The criteria for the Steam Line Break event is
the radiological criteria in 10 CFR 100.
Evaluation Completion Schedule Date:
December 1, 1998
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