ML20134F658
| ML20134F658 | |
| Person / Time | |
|---|---|
| Issue date: | 02/05/1997 |
| From: | Chaffee A NRC (Affiliation Not Assigned) |
| To: | Sozzi G GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 9702100088 | |
| Download: ML20134F658 (5) | |
Text
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February 5,1997 Gary Sozzi. Services General Manager Technical and Modifications Services 4
GE Nuclear Energy
, 175 Curtner Ave. Mail Code 706 San Jose, CA 95125
SUBJECT:
REQUEST FOR A TECHNICAL REVIEW OF A DRAFT INFORMATION NOTICE REGARDING NONCONSERVATIVE ERRORS AND CHANGES IN GENERAL ELECTRIC NUCLEAR ENERGY LARGE-BREAK LOSS-OF-COOLANT ACCIDENT EVALUATION MODEL AND COMPLIAVE WITH 10 CFR 50.46(a)(3) 4 1
Dear Mr. Sozzi:
The U.S. Nuclear Regulatory Commission is planning to issue an information notice discussing recent staff findings related to the review of General Electric Nuclear Energy large-break loss-of-coolant accident 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 Reaulations [10 CFR 50.46(a)(3)] concerning the reporting of ECCS cooling model changes and
, errors. We ask that you review the enclosed draft of that information notice to ensure the technical information is accurate. Your cooperation in this matter is appreciated. Please return any comments you may have as soon as 2
possible. A copy of this request and your response will be placed in the 4
Public Document Room for review by the public. Your response should be mailed j to:
U.S. Nuclear Regulatory Commission '
Washington, DC 20555-0001' ATTN: Stephen Koenick, NRR/PECB j
MAIL STOP: 011E4 4
Please address any questions you may have on this matter to Stephen Koenick of my staff. Mr. Koenick may be reached by phone (301) 415-2841. If no comments are received by close of business February 14, 1997, we will assume the technical information in the notice is correct.
l l
[ Original signed by Robert L Dennig}
for Alfred E. Chaffee, Chief l Events Assessment and l Generic Communications Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation
Enclosure:
Draft Information Notice DISTRIBUTION 9TTMartin y DRPM R/F l 7
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' UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555-0001 i
- February XX,1997 j
NRC INFORMATION NOTICE 97-XX: NONCONSERVATIVE ERRORS AND CHANGES IN A LARGE-BREAK LOSS-OF-COOLANT ACCIDENT 1
EVALUATION MODEL OF A FUEL VENDOR AND l COMPLIANCE WITH 10 CFR 50.46(a)(3) l Addressees l
l All holders of operating licenses or construction permits for nuclear power reactors and all j reactor fuel vendors.
i Purcose j The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert l addressees about the recent staff findings related to the review of Siemens Power i
Corpcration (SPC, fornerly Exxon Nuclear) large-break (LB) loss-of-coolant accident (LOCA) emergency core cooling system (ECCS) analysis evaluation model changes and also to remind licensees and ;eactor fuel vendors of the requirements contained in Section
- 50.46(a)(3) of Title 10 of the Code of Federal Reaulations [10 CFR 50.46(a)(3)] conceming
- 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 j NRC requirements; therefore, no specific action or written response is required.
i Description of Circumstances Recently identified changes and errors in SPC 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 i
10 CFR 50.46, " Acceptance Criteria for Emergency Core Cooling Systems for Light Water l Nuclear Power Reactors."
j SPC LBLOCA ECCS Evaluation Model Changes j
The SPC LPLOCA ECCS model, TOODEE2, was originally 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 i
changes to the NRC-approved fuel cooling test facility (FCTF) reflood heat transfer coefficient l correlation used in TOODEE2.
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, During August 1995, the NRC met with SPC about the LBLOCA ECCS evaluation model. As i
a result of that meeting, the staff sent a letter to SPC, dated November 13,1995
[9511150211), that identified problems conceming changes in the TOODEE2 computer code 4
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' IN 97-xx February ,1997
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l specifically related to the 1991 changes to the NRC-approved FCTF reflood heat transfer i
coefficient correlation and the significance of the code changes. The staff then requested in i 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 staff's approval of the code in July 1986.
4 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 vender (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). Eariier in 1996, two impacts had been reported by GE to the licensee and when reviewing the handling of this information during the audit, three additionalimpacts not previously reported to the licensee were discovered, dating back to 1990,1992, and 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 and as required by 10 CFR 50.46. The cumulative PCT impact was previously known to be 35 'F (19 *C); however, on the basis of the errors identified during the audit, the value is now raised to 100 'F (56 *C) exceeding the 50 'F (28 *C) reporting threshold. The licensee's recalculated PCT still remains below the ECCS acceptance criteria of 2200 'F (1200 *C).
The licensee stated that GE had been submitting annual reports to the NRC on behalf of its boiling water reactor customers since 1990. Although the audit determined that the cumulative change to the PCT was in error for the Hope Creek licensee, it was not clear at this time whether the vendor reports to the NRC were either wholly or partially in error, or if other licensees were similarly affected.
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- Discussion 1
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).
l 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 j SPC's LBLOCA methodology (the review experience of the SPC LOCA evaluation model 2
changes) and the Hope Creek QA audit indicate that licensees may not be closely monitoring i the work of their respective fuel vendors. When the error in the 1986 model was discovered j 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 dKferent by more than 50*F 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 l magnitudes of the respective tempuature changes is greater than 50 'F." l
! Licensees may not be performing adequate assessments of errors when they are aware of l them. Furthermore, licensees' audits of SPC's code changes appear to have been ineffective l in identifying the technicalinadequacy of the code changes. It should be noted that
- 10 CFR 50.46 allows fuel vendors or licensees to make code changes without the staff's 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.
j lt also appears that licensees may not be monitoring the cumulative effect of the code 1
changes. In a given year, the impact of the code change may be less than 50 'F (28 *C) and hence the change is not significant. But the impact of the code changes over several years together can exceed 50 'F (28 *C) and, therefore, will be reportable as significant.
! Section 50.46 places the responsibility for the reporting of code changes on the licensees.
i Some licensees have apparently considered that the annual reports 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 j the limiting ECCS analysis to the Commission at least annually as specified in 950.4. If the
- change or error is significant, the applicant or licensee shall provide this report within
- 30 days...." The reports submitted by the fuel vendors will not satisfy these reporting i
requirements; however, licensees are allowed to refer to the vendor's annual reports. As stated in 10 CFR Part 50, Appendix B, Section Vil,"The effectiveness of the control of quality by contrac. ors 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 summary, licensees are reminded that to meet the ECCS acceptance criteria their
! responsibilities include:
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IN 97-xx February ,1997 j ,
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4 (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) Individuallicensees are responsible to assess effectiveness 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 i
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager. 1 Thomas T. Martin, Director Division of Reactor Program Management !
Office of Nuclear Reactor Regulation
. Technical contacts: George Thomas, NRR Joseph L. Staudenmeier, NRR i l (301) 415-1814 (301) 415-2869
] E-mail: gxt@nrc. gov E-mail: jls4@nrc. gov Stephen Koenick, NRR (301) 415-2841
{ E-mail: ssk2@nrc. gov
Attachment:
List of Recently issued NRC information Notices 1
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