ML20115H341
| ML20115H341 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 07/17/1996 |
| From: | Wadley M NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9607230066 | |
| Download: ML20115H341 (5) | |
Text
i Northern States Power Company Pralrie Island Nuclear Generating Plant l
1717 Wakonado Dr. East l
Welch. Minnesota 55089 l
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July 17,1996 10 CFR Part 2 l
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U S Nuclear Regulatory Commission l
Attn: Document Control Desk i
Washington, DC 20555 i
PRAIRIE ISLAND NUCLEAR GENERATING PLANT l
Docket Nos.50-282 License Nos. DPR-42 50-306 DPR-60 Reolv to Notice of Violation (Insoection Reoort 96006) l l
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Your letter of June 29,1996, which transmitted Inspection Report No. 96006, required a response to a Notice of Violation. Our response to the violation is contained in the attachment to this letter.
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In this letter we have made no new Nuclear Regulatory Commission commitments.
Please contact Jack Leveille (612-288-1121, Ext. 4662) if you have any questions related to this letter.
//b' W
I Michael D Wadley Plant Manager l
Prairie Island Nuclear Generating Plant l
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Regional Administrator - Region Ill, NRC Senior Resident inspector, NRC t
NRR Project Manager, NRC J E Silberg
Attachment:
RESPONSE TO NOTICE OF VIOLATION 7887" nee 398?s2e2
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RESPONSE TO NOTICE OF VIOLATION VIOLATION 10 CFR Part 50, Appendix B, Criterion V," Instructions, Procedures, and Drawings,"
requires, in part, that activities affecting quality shall be prescribed by documented instructions, procedures, or drawings of a type appropriate to circumstances and shall be accomplished in accordance with these instructions, procedures or drawings.
The Reload Safety Evaluation procedure, NAP 2.102T, Rev.12, effective November 15, 1993, Section 6.5.14, listed four acceptance criteria for performing the main steam line break (MSLB) event analysis. The third acceptance criterion stated: "the maximum clad temperature calculated to occur at the core hot spot must not exceed 2750*F."
The Policy and Procedure Directive procedure, NAP 1.001 A, Rev. 09, effective March 1, 1993, Section 6.2 and 6.3, required independent review and verification of safety-related analyses performed by Fuel Resources staff.
Contrary to the above:
a.
For the MSLB analysis performed for the Prairie Island Unit 1 Cycle 17, dated June 1994, the licensee did not verify maximum calculated clad temperature would not exceed 2750*F.
b.
For the MSLB analysis performed for the Prairie Island Unit 2 Cycle 16, dated April 1994, the licensee did not verify maximum caiculated clad temperature would not exceed 2750*F.
c.
For the MSLB analysis performed for the Prairie Island Unit 2 Cycle 17, dated May 1995, the licensee did not verify maximum calculated clad temperature would not exceed 2750*F.
d.
The licensee did not review or verify the acceptance criteria specified in the NAP 1.001 A procedure for the MSLB analyses for the three cycles listed above.
This is a Severity Level IV violation (Supplement 1).
RESPONSE TO VIOLATION
Background:
When performing a safety analysis for a core, it is standard practice for the Nuclear Analysis Department (NAD) to begin by reviewing the analysis for a previous core. The core physics data of the new core is compared with that of a previous core (s) to determine if previous analysis will bound the new core. If a previous analysis bounds
Attachment July 17,1996 Page 2 the new core, that analysis is not repeated for the new core. This limits the amount of analysis that must be performed for the new core. The acceptance criteria for the parameters of concern is given in the Topical Report and in a NAD procedure. Both the Topical Report and the NAD procedure give general guidance, but not specific instructions. It is standard practice that the total analysis package, called the Reload Safety Evaluation (RSE), is verified by another person and is also design reviewed by a consultant. Nevertheless, a Peak Clad Temperature (PCT) analysis was not performed for the Unit 2 Cycle 17 (P217) core or the Unit 1 Cycle 17 (P117) core.
The safety analysis for Prairie Island Unit 1 Cycle 17 (referred to as P117) was completed and verified in May of 1994. This was the first core reload for which the Main Steam Line Break accident (MSLB) analysis showed that DNBR would fall below the minimum that would assure no fuel failures (DNBR > 1.45). The acceptance criteria of interest for the MSLB for this event are:
DNBR > 1.45; if the DNBR limit is reached, then the number of fuel rods calculated to exceed the DNBR limit shall not exceed the maximum number calculated to maintain off site doses within 10CFR100 limits e PCT < 2750 'F lt is known that PCT cannot approach the 2750 'F limit unless DNBR falls below its limit. Therefore a specific analysis for PCT does not need to be performed unless the DNBR limit is reached. P117 was the first analysis that showed that the DNBR limit was reached, however no analysis for PCT was performed. Neither the verification process nor the review process detected this oversight in the P117 analysis package.
Clarification / Minor Corrections to the Statement of the Violation:
Regarding the " Reload Safety Evaluation procedure" above:
Reload Safety Evaluation procedure NAP 2.102T, dated November 15,1993 was Rev.10 rather than Rev.12.
Regarding item "b" above:
By showing that no fuel pins exceeded the DNBR limit, the Prairie Island Unit 2 Cycle 16 (P216) analysis dated October 1993 did verify that the maximum calculated clad temperature would not exceed 2750 F. However, subsequent to that analysis a question arose regarding the assumed mixing of the water in the lower plenum. This issue was temporarily resolved by adding additional conservatism in the Prairie Island Unit 1 Cycle 17 (P117) analysis performed in May 1994. This P117 analysis was performed in such a manner that it bounded operation of P216, and thereby addressed the inlet mixing question for P216.
However the P117 analysis did not verify that the maximum calculated clad f
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Attachment July 17.1996 Page 3 temperature would not exceed 2750 F. Therefore it was not verified that the maximum ca!culated clad temperature for P216 would not exceed 2750 F.
Regarding item "d" above:
Procedure NAP 1.001A does not specify the acceptance criteria for the MSLB.
The acceptance criteria for the MSLB accident is specified in procedure NAP 2.102T. Procedure NAP 1.001 A does specify that the verification shall confirm traceability of input and correctness, while the design review is to confirm j
the correctness of the methodology used. Contrary to this, neither the verifiers nor the design reviewer confirmed that the all the acceptance criteria in NAP 2.102T had been met.
Reason for the Violation:
.I The individuals involved in performing, verifying, and reviewing the above analyses failed to recognize that when the calculations showed fuel pins had exceeded the DNBR limit, a calculation of the maximum peak clad temperature was necessary to verify that its limit was not exceeded. Self checking by these individuals was not sufficient to detect the omission. Additionally, the procedures did not require documentation showing that each individual acceptance criteria was met and how it was met.
Corrective Steos Taken and Results Achieved A bounding MSLB analysis out to 13,000 mwd /mtu was completed in February 1996, which verified that the maximum calculated clad temperature for Prairie Island Unit 2 Cycle 17 (the current cycle) would not exceed 2750*F. A cycle specific MSLB analysis was completed for the entire Prairie Island Unit 2 Cycle 17 (the current cycle) on May 7 1996, which verified that the maximum calculated clad temperature would not exceed 2750*F.
A bounding MSLB analysis out to 13,000 mwd /mtu was completed in February 1996, which verified that the maximum calculated clad temperature for Prairie Island Unit 1 Cycle 18 (the current cycle) would not exceed 2750 F prior to the beginning of the cycle. Prior to exceeding 13,000 mwd /mtu (wh!ch will not be reached until February 1997) NSP will complete an additional analysis to verify that the maximum calculated clad temperature will not exceed 2750 F out to the planned end of cycle exposure.
No additional analyses were performed for Prairie Island Unit 2 Cycle 16 nor for Prairie Island Unit 1 Cycle 17 since both of these cycles had ended before the investigation of the discrepancy was completed.
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Attachment July 17,1996 Page 4 Corrective Steos That will be Taken to Avoid Further Violations:
The following steps were committed to in Licensee Event Report 96-05, March 81996:
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- 1. The Nuclear Analysis Department will develop a summary check sheet, i
identifying each individual acceptance criteria, the results of the analysis I
performed or the justification for not needing to do the analysis.
- 2. The Nuclear Andysis Department will develop more detailed procedures for the limiting transients.
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- 3. The Nuclear Analysis Department willimra, s the consultant design review process.
Items numbered 1 & 3 above were completed on May 6,1996, with the inclusion of checklis's into Nuclear Analysis & Design procedure NAP 2.102T Rev.12.
Item Numbered 2 above is scheduled for completion by December 31,1996.
The Date When Full Comoliance Will be Achieved:
Full compliance has been achieved.
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