Information Notice 1997-15, Reporting of Errors and Changes in Large-Break Loss-of-Coolant Accident Evaluation Models of Fuel Vendors and Compliance with 10 CFR 50. 46(a)(3)
KU
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
April 4,1997
REPORTING OF ERRORS AND CHANGES IN
LARGE-BREAK LOSS-OF-COOLANT ACCIDENT
EVALUATION MODELS OF FUEL VENDORS AND
COMPLIANCE WITH 10 CFR 50.46(a)(3)
Addressees
All holders of operating licenses or construction permits for nuclear power reactors and all
reactor fuel vendors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees about two recent staff findings related to the review of large-break (LB) loss-of- coolant accident (LOCA) emergency core cooling system (ECCS) analysis evaluation model
changes and also to remind licensees and reactor fuel vendors of the requirements contained
in Section 50.46(a)(3) of Title 10 of the Code of Federal Regulations [10 CFR 50.46(a)(3)]
concerning the reporting of ECCS cooling model changes and errors. It is expected that
recipients will review the information for applicability to their facilities and consider actions, as
appropriate, to avoid similar problems. However, suggestions contained in this information
notice are not NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances
Recently identified changes and errors in Siemens Power Corporation (SPC, formerly Exxon
Nuclear) and General Electric (GE) LBLOCA analysis models have led to a series of 30-day
reports and 10 CFR 50.72 reports as required by 10 CFR 50.46, "Acceptance Criteria for
Emergency Core Cooling Systems for Light Water Nuclear Power Reactors."
SPC LBLOCA ECCS Evaluation Model Changes
The SPC LBLOCA ECCS model, TOODEE2, was approved by the NRC staff to meet the
requirements of 10 CFR 50.46 in a letter dated July 8, 1986 [Accession number
8607150319], from D. M. Crutchfield (NRC) to G. Ward (Exxon). In 1991, SPC had made
changes to the NRC-approved fuel cooling test facility (FCTF) reflood heat transfer coefficient
correlation used in TOODEE2.
During August 1995, the NRC met with SPC about the LBLOCA ECCS evaluation model. As
a result of that meeting, the staff sent a letter to SPC, dated November 13, 1995
[95111502111, that identified problems concerning changes in the TOODEE2 computer code
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IN 97-15 April 4, 1997 specifically related to the 1991 changes to the NRC-approved FCTF reflood heat transfer
coefficient correlation and the significance of the code changes. The staff then requested in
a letter dated March 13, 1996 [9603150002], that SPC formally submit to the staff for its
review and approval all model revisions and corrections implemented in TOODEE2 since the
staffs approval of the code in July 1986.
On June 2, 1996, SPC submitted topical report XN-NF-82-20, "EXEM/PWR Large Break
LOCA ECCS TOODEE2 Updates," Revision 1, Supplement 5 [9606260239], which described
the updates made in the TOODEE2 computer code between 1986 and 1991. TOODEE2 is
part of the evaluation model used by SPC for pressurized-water reactors. The staff has
completed its review of this report and has concluded that the proposed LBLOCA-ECCS
model (i.e., the 1991 model) is not acceptable and the previously approved model (i.e., the
1986 model) contains an unacceptable error. This information was formally communicated to
SPC in a safety evaluation enclosed in a letter dated November 29, 1996 [9612040294).
After concluding that the 1991 model was unacceptable, the staff met with SPC and those
licensees using SPC's LBLOCA evaluation model on October 16, 1996, to discuss the
unacceptable error in the 1986 model. The staff also requested and received information
from the licensees that demonstrated that they were in compliance with 10 CFR 50.46 (see
meeting summary dated November 5, 1996 [9611140318]).
Public Service Electric & Gas (PSE&G) Audit of GE
During a recent licensee-conducted quality assurance (QA) audit of the fuel vendor (GE -
Wilmington, North Carolina), PSE&G, the licensee of Hope Creek Nuclear Generating Station, identified a weakness in GE's tracking of errors and changes in the LOCA evaluation models.
Between 1990 and 1995, information sent to the licensee indicated that there had been no
known impact on the calculated peak cladding temperature (PCT). Earlier in 1996, two
impacts had been reported by GE to the licensee and when reviewing the handling of this
information during the audit, three additional impacts not previously reported to the licensee
were discovered, dating back to 1990, 1992, ard 1993. In addition, the audit determined that
GE had not been tracking the cumulative impact of errors and changes on the PCT as
expected by the licensee. The cumulative PCT impact was previously known to be 35 OF
(19 OC); however, on the basis of the errors identified during the audit, the value is now
raised to 100 OF (56 OC) exceeding the 50 'F (28 'C) reporting threshold. The licensee's
recalculated PCT still remains below the ECCS acceptance criteria of 2200 OF (1200 OC).
In a letter to the NRC dated February 17, 1997 [9703060067], GE characterized the licensee- identified weakness as an issue of timeliness of notifications to utilities of errors and changes
in the LOCA evaluation models. Furthermore, notification about changes or errors identified
during the 1990 to 1995 period were provided by GE on an annual basis. Because
notification by GE to boiling-water reactor BWR licensees on individual impacts less than
50 OF (28 OC) were not provided as they occurred, the BWR licensees did not have the
required information to fully comply with the requirements of 10 CFR 50.46 [specifically the
requirement to report within 30 days a cumulative PCT impact greater than 50 OF (28 OC)].
April 4, 1907 Discussion
Although the LOCA analyses are performed by the fuel vendors, licensees are responsible for
compliance with the regulations related to the LOCA analysis, that is, 10 CFR 50.46(a).
Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model. The staff's recent interactions with the licensees using the
SPC's LBLOCA methodology (the review experience of the SPC LOCA evaluation model
changes) and the Hope Creek QA audit indicate that licensees may not be closely monitoring
the work of their respective fuel vendors. When the error in the 1986 model was discovered
and when SPC changed the TOODEE2 code in 1991, the resulting changes in the PCT were, in some cases, significant, and the responsible licensees were not aware of the significant
changes. "Significant" is defined in 10 CFR 50.46(a)(3)(i) as follows: "a significant change or
error is one which results in a calculated peak fuel cladding temperature different by more
than 500F from the temperature calculated for the limiting transient using the last acceptable
model, or is a cumulation of changes and errors such that the sum of the absolute
magnitudes of the respective temperature changes is greater than 50 OF."
Licensees may not be performing adequate assessments of errors when they are aware of
them. Furthermore, licensees' audits of SPC's evaluation model changes appear to have
been ineffective in identifying the technical inadequacy of the changes. It should be noted
that 10 CFR 50.46 allows fuel vendors or licensees to make evaluation model changes
without the staffs prior approval; however, the licensees are responsible for identifying any
deficiencies in the change process and reporting them to the NRC staff accordingly. In
addition, the licensee determines whether the changes are significant.
It also appears that licensees may not be monitoring the cumulative effect of the evaluation
model changes. In a given year, the impact of the evaluation model change may be less
than 50 'F (28 OC) on the limiting PCT calculated with the last acceptable model and hence
the change is not significant. But the impact of the evaluation model changes over several
years together can exceed 50 OF (28 OC) and, therefore, will be reportable as significant.
Section 50.46 places the responsibility for the reporting of evaluation model changes on the
limiting PCT calculated with the last acceptable model on the licensees. Some licensees
have apparently considered that the annual notifications sent by the fuel vendor are sufficient
to meet the requirements under 10 CFR 50.46(a)(3)(ii). Specifically, "the applicant or
licensee shall report the nature of the change or error and its estimated effect on the limiting
ECCS analysis to the Commission at least annually as specified in §50.4. If the change or
error is significant, the applicant or licensee shall provide this report within 30 days...." The
notifications submitted by the fuel vendors will not satisfy these reporting requirements;
however, licensees are allowed to refer to the vendor's annual notifications. As stated in
10 CFR Part 50, Appendix B, Section VII, "The effectiveness of the control of quality by
contractors and subcontractors shall be assessed by the applicant or designee at intervals
consistent with the importance, complexity, and quantity of the product or services."
IN 97-15 April 4, 1997 In summary, licensees are reminded that to meet the ECCS acceptance criteria their
responsibilities include:
(1) Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model.
(2)
Section 50.46(a)(3)(ii) requires licensees to report changes and/or errors and their
estimated effects on the limiting ECCS analysis to the Commission at least annually, and if the change or error is significant, the licensee shall provide this report within
30 days.
(3)
Individual licensees are responsible to assess effectiveness of the control of quality of
ECCS evaluation models provided by the vendors as required by Part 50, Appendix B.
Meaningful technical audits may be necessary to meet Appendix B.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: George Thomas, NRR
Joseph L. Staudenmeier, NRR
(301) 415-1814
(301) 415-2869 E-mail: gxt@nrc.gov
E-mail: jils4@nrc.gov
Eric Benner, NRR
(301) 415-1171 E-mail: ejbl@nrc.gov
Attachment: List of Recently Issued NRC lnformation Notice
of nz3>t PIe
41 i- e
Attachment
April 4, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
97-14
Assessment of Spent
Fuel Pool Cooling
03/28/97
All holders of OLs
or CPs for nuclear
power reactors
97-13
97-12
Deficient Conditions
Associated with Pro- tective Coatings at
,Juclear Power Plants
Potential Armature
Binding in General
Electric Type HGA
Relays
03/24/97
03/24/97
All holders of OLs
or CPs for nuclear
power reactors
All holders of OLs
or CPs for nuclear
power reactors
92-27, Supp. 1
Thermally Induced
Accelerated Aging
and Failure of ITE/
Gould A.C. Relays
Used in Safety-Related
Applications
03/21/97
All holders of OLs
or CPs for nuclear
power reactors
97-11
Cement Erosion from
Containment Subfounda- tions at Nuclear Power
Plants
03/21/97
All holders of OLs
or CPs for nuclear
power reactors
97-10
97-09
Liner Plate Corrosion
in Concrete Containments
Inadequate Main Steam
Safety Valve (MSSV)
Setpoints and Perform- ance Issues Associated
with Long MSSV Inlet
Piping
03/13/97
03/12/97
All holders of OLs
or CPs for power
reactors
All holders of OLs
or CPs for nuclear
power reactors
OL = Operating License
CP = Construction Permit
IN 97-15 April 4, 1997 In summary, licensees are reminded that to meet the ECCS acceptance criteria their
responsibilities include:
(1) Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model.
(2) Section 50.46(a)(3)(ii) requires licensees to report changes and/or errors and their
estimated effects on the limiting ECCS analysis to the Commission at least annually, and if the change or error is significant, the licensee shall provide this report within
30 days.
(3)
Individual licensees are responsible to assess effectiveness of the control of quality of
ECCS evaluation models provided by the vendors as required by Part 50, Appendix B.
Meaningful technical audits may be necessary to meet Appendix B.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
original signed by T.R. Quay
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: George Thomas, NRR
Joseph L. Staudenmeier, NRR
(301) 415-1814
(301) 415-2869 E-mail: gxt@nrc.gov
E-mail: jls4@nrc.gov
Eric Benner, NRR
(301) 415-1171 E-mail: ejbl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Tech Editor has reviewed and concurred on 12/18/96 DOCUMENT NAME: 97-15.IN
OFC
TECH
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CONTACT
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NAME
EBenner
JLyons*
AEChaffee*
TTMartin
GThomas*
JStaudenmeier
DATE
1/14197
3/07/97
03/21/97
313V97 OFFICIAL RECORD COPY]
.NU IN97-xx
March,
1997 In summary, licensees are reminded that to meet the ECCS acceptance criteria their
responsibilities include:
(1) Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model.
(2) Section 50.46(a)(3)(ii) requires licensees to report changes and/or errors and their
estimated effects on the limiting ECCS analysis to the Commission at least annually, and if the change or error is significant, the licensee shall provide this report within
30 days.
(3) Individual licensees are responsible to assess effectiveness of the control of quality of
ECCS evaluation models provided by the vendors as required by Part 50, Appendix B.
Meaningful technical audits may be necessary to meet Appendix B.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: George Thomas, NRR
Joseph L. Staudenmeier, NRR
(301) 415-1814
(301) 415-2869 E-mail: gxt@nrc.gov
E-mail: jls4@nrc.gov
Eric Benner, NRR
(301) 415-1171 E-mail: ejbl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:1SSK2%IN5046.RV2 OFC
TECH
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CONTACT
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TTMartin
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March , 1997 In summary, licensees are reminded that to meet the ECCS acceptance criteria their
responsibilities include:
(1) Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model.
(2)
Section 50.46(a)(3)(ii) requires licensees to report changes and/or errors and their
estimated effects on the limiting ECCS analysis to the Commission at least annually, and if the change or error is significant, the licensee shall provide this report within
30 days.
(3)
Individual licensees are responsible to assess effectiveness of the control of quality of
ECCS evaluation models provided by the vendors as required by Part 50, Appendix B.
Meaningful technical audits may be necessary to meet Appendix B.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
George Thomas, NRR
(301) 415-1814 E-mail: gxt~nrc.gov
Joseph L. Staudenmeier, NRR
(301) 415-2869 E-mail: jls4@nrc.gov
Eric Benner, NRR
(301) 415-1171, E-mail: ejbl@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:XSSK2XIN5046.RV2 OFC
TECH
C:SXRB:DSSA
C:PECB:DRPM
D:DRPM
CONTACT
S
NAME
EBennei l1 T1Lyons*
AEChaffee
TTMartin
GThomas
JStaudenmeier
DATE
1/14/97
3/07/97
//97
1/97 OFFICIAL RECORD COPY] V
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IN 97-xx
February , 1997 In summary, licensees are reminded that to meet the ECCS acceptance criteria their
responsibilities include:
(1) Section 50.46(a)(1)(i) requires licensees to calculate ECCS cooling performance with an
acceptable evaluation model.
(2) Section 50.46(a)(3)(ii) requires licensees to report changes andlor errors and their
estimated effects on the limiting ECCS analysis to the Commission at least annually, and if the change or error is significant, the licensee shall provide this report within 30
days.
(3)
Individual licensees are responsible to assess effectiveness of the control of quality of
ECCS evaluation models provided by the vendors as required by Part 50, Appendix B.
Meaningful technical audits may be necessary to meet Appendix B.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Thomas T. Martin, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Joseph L. Staudenmeier, NRR
(301) 415-1814
(301) 415-2869 E-mail: gxt@nrc.gov
E-mail: jis4@nrc.gov
Stephen Koenick, NRR
(301) 415-2841 E-mail: ssk2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\SSK2\\IN5046.RV2 T
OFC
TECH
CONTACT
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NAME
SKoenick S$¶k
GThomaser
JStaudenmeier
DATE
1/14/97 I
UFFICIAL RECORD COPY]