ML20239A067
| ML20239A067 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 09/02/1998 |
| From: | Richard Laufer NRC (Affiliation Not Assigned) |
| To: | Leslie Liu IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT |
| References | |
| GL-97-04, GL-97-4, IEB-96-003, IEB-96-3, TAC-M99987, NUDOCS 9809080127 | |
| Download: ML20239A067 (7) | |
Text
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Mr.' Lee Liu September 2, 1998 Ch:irmin of the Botrd and Chief Executive Officer IES Utilities Inc.
200 First Street, SE.
P.O. Box 351 Cedar Rapids, IA 52406-0351
SUBJECT:
- DISCUSSION OF RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON GENERIC LETTER 97-04,
- ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS," - DUANE ARNOLD ENERGY CENTER
- (TAC NO.- M99987)
Dear Mr. Liu:
By letter dated May 14,1998, the staff requested additional information pertaining to your January 5,1998, Generic Letter 97-04 response for the Duane Amold Energy Center (DAEC).
By letter dated June 12,1998, your responded to the request for additional !nformation (RAI).
Based on your response to the RAl, it appears to the staff that the DAEC will be outside its -
licensing basis with respect to credit for containment overpressure when the proposed resolution to Bulletin 96-03 is implemented. Therefore, the staff should review your resolution of Bulletin 96-03 with respect to containment overpressure prior to its implementation. The i
l staffs assessment of your RAI response is enclosed. Should you have any questions, please contact me at 301-415-1373.
Sincerely, d.
Original signed by:
Richard J. Laufer, Project Manager Project Directorate lll-3 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket No. 50-331
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1 Mr. Lee' Liu september 2, 1998 4
Ch:irm:.n of the Bo:rd and Chief Executive Officer IES Utilities Inc.
200 First Street, SE.
P.O. Box 351 Cedar Rapids, IA 52406-0351
SUBJECT:
DISCUSSION OF RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON GENERIC LETTER 97-04, " ASSURANCE OF SUFFICIENT NET POSITIVE l
SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS," - DUANE ARNOLD ENERGY CENTER (TAC NO. M99987)
Dear Mr. Liu:
By Ictter dated May 14,1998, the staff requested additional information pertaining to your January 5,1998, Generic Letter 97-04 response for the Duane Arnold Energy Center (DAEC).
By letter dated June 12,1998, your responded to the request for additional information (RAl).
Based on your response to the RAI, it appears to the staff that the DAEC will oe outside its licensing basis with respect to credit for containment overpressure when the proposed resolution to Bulletin 96-03 is implemented. Therefore, the staff should review your resolution of Bulletin 96-03 with respect to containment overpressure prior to its implementation. The staff's assessment of your RAI response is enclosed. Should you have any questions, please contact me at 301-415-1373.
Sincerely, Original signed by:
Richard J. Laufer, Project Manager Project Directorate lll-3 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket No. 50-331
Enclosure:
As stated cc w/ encl.: See next page Distribution :
Docket File DSkay PUBLIC KKavanagh PD3-3 Reading EAdensam(EGA1)
DOCUMENT NAh/IE: G:\\DUANEARN\\DA99987.LTR To receive a copy of this document, indicate in the box: "C" = Copy without enclosures "E" = Copy with enclosures "N" = No copy l OFFICE PM:PD33 F#
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%,.....,o September 2, 1998 Mr. Lee Liu Chairman of the Board and Chief Executive Officer IES Utilities Inc.
200 First Street, SE.
P.O. Box 351 Cedar Rapids, IA 52406-0351
SUBJECT:
DISCUSSION OF RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION ON GENERIC LETTER 97-04, " ASSURANCE OF SUFFICIENT NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL PUMPS," - DUANE ARNOLD ENERGY CENTER (TAC NO. M99987)
Dear Mr. Liu:
By letter dated May 14,1998, the staff requested additional information pertaining to your January 5,1998, Generic Letter 97-04 response for the Duane Arnold Energy Center (DAEC).
j By letter dated June 12,1998, your responded to the request for additional information (RAl).
I Based on your response to the RAI, it appears to the staff that the DAEC will be outside its licensing basis with respect to credit for containment overpressure when the proposed resolution to Bulletin 96-03 is implemented. Therefore, the staff should review your resolution of Bulletin 96-03 with respect to containment overpressure prior to its implementation. The staff's assessment of your RAI response is enclosed. Should you have any questions, please contact me at 301-415-1373.
Sincerely, O
Richard J. Laufer, Project Manager Project Directorate lll-3 Division of Reactor Projects lil/lV l
Office of Nuclear Reactor Regulation Docket No. 50-331
Enclosure:
As stated cc w/ encl.: See next page l
c L--------.---_-------
y i
Lee Liu Duane Amold Energy Center IES Utilities Inc.
cc:
Jack Newman, Esquire Al Gutterman, Esquire Morgan, Lewis, & Bockius 1800 M Street, NW.
- Washington, DC 20036-5869 Chairman, Linn County Board of Supervisors -
Cedar Rapids, IA 52406 IES Utilities Inc.
ATTN: Gary Van Middlesworth Plant Superintendent, Nuclear 3277 DAEC Road Palo,IA 52324 John F. Franz, Jr.
Vice President, Nuclear.
l Duane Arnold Energy Center.
3277 DAEC Road Palo,IA 52324 i
Ken Peveler Manager of Regulatory Performance l
Duane Arnold Energy Center i
3277 DAEC Road Palo,lA 52324 l
U.S. Nuclear Regulatory Commission Resident inspector's Office l
~ Rural Route #1 Palo,IA 52324 Regional Administrator, Rill i
U.S. Nuclear Regulatory Commission 801 Warrenville Road
~ Lisle, IL 60532-4531 Parween Baig Utilities Division Iowa Department of Commerce Lucas Office Building,5th floor.
Des Moines,IA 50319
.( -
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ASSESSMENT OF DUANE ARNOLD ENERGY CENTER'S JUNE 12.1998. RESPONSE TO A REQUEST FOR ADDITIONAL INFORMATION ON GENERIC LETTER 97-04.
Backaround By letter dated January 5,1998, IES Utilities, the licensee, responded to Generic Letter 97-04,
" Assurance Of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps," for the Duane Arnold Energy Center (DAEC). By letter l
dated May 14,1998, the NRC staff requested the following additionalinformation:
- 1) Have all the errors found in the NPSH (net positive suction head) analyses been corrected?
- 2) When will the new containment pressure and temperature analysis be complete?
)
- 3) The staff believes that the Duane Amoldlicensing basis needs to be clarified with regard to credit for containment overpressure, especially since the potential exists that I
an increased reliance on containment overpressure will be needed to resolve Bulletin l
96-03 issues. What are yourplans/ schedule for clarifying the licensing basis?
By letter dated June 12,1998, IES Utilities responded to the staff's RAl. In its response to question 3, IES Utilities stated that:
"The NPSH analyses will be revised to reflect the strainer modification and to support DAEC's resolution of Bulletin 96-03. As part of this effort, a re-evaluation of the margins identified in the original NRC SE and Supplement 1 will be performed. The DAEC believes adequate NPSH will be available for the ECCS pumps without any increase in reliance on containment overpressure. However, the calculations can not be finalized until the LTR and URG are approved by the NRC. Upon resolution of Bulletin 96-03, the DAEC Updated Final Safety Analysis Report (UFSAR) will be revised, as appropriate, in I
accordance with 10 CFR 50.71(e) and 10 CFR 50.59."
It appears to the staff that DAEC believes that an " increased reliance on containment I
overpressure" will only occur when there is a reduction in the margin between the amount of containment overpressure required to ensure adequate NPSH and the containment overpressure available. However, the staff defines " increased reliance on containment overpressure" as any increase in the absolute amount of containment overpressure required to ensure adequate NPSH. Additionally, the staff believes the plant configuration evaluated in the original NRC SE (January 23,1973) and Supplement 1 (March 2,1973) does not reflect the current configuration of the plant due to the use of new calculations and methodologies.
Discussion i
l In the original NRC SE dated January 23,1973, the staff made the following conclusion with regard to adequate NPSH for the ECCS pumps:
1
D
. "The applicant analyzed the availability of adequate net positive suction head (NPSH) for all ECCS pumps in conformance with Safety Guide No.1 which requires that there be no reliance on calculated increases in containment pressure. The most limiting case occurs during the long term transient following the design basis LOCA when one core spray and one RHR pump will be running continuously. In this operating condition, the NPSH requirement for the spray pump is the limiting parameter. The analysis shows that a containment pressure margin of about 1.5 psi will be avai!able throughout the long-term post-LOCA period to assure adequate NPSH for the core spray pumps for the above cited conditions. Although the design does not fully meet the provisions of the safety guide, we have concluded that the applicant's analysis is conservative and that there should be adequate NPSH to the ECCS pumps, in the unlikely event of a LOCA."
Supplement 1 of the original NRC SE revised the available containment pressure margin from 1.5 to 2.7 psi. This margin was based on containment pressure of 14.7 psia as shown in the DAEC UFSAR Figure 5.4-15. The staff found the pressure margin to be acceptable, after considering the conservative methods used to analyze the available NPSH and the margin l
available.
Since the issuance of the original licensing SE, errors have been identified in the NPSH calculations and changes have been made to both the calculations and methodology. These errors and changes are discussed in NRC System Operational Performance Inspection Report 50-331/97006 (DRS) and Notice of Violation dated September 2,1997, the DAEC Generic Letter 97-04 Response dated January 5,1998, and the DAEC Response to the NRC GL 97-04 l
RAI dated June 12,1998. The errors identified included nonconservative flow rates, incorrect piping configurations, nonconservative torus water temperature, and incorrect strainer headloss. The results of the corrected calculation were presented in the DAEC Response to GL 97-04. In response to question 4 of the GL, DAEC indicated that only 1.3 psi of containment overpressure (i.e., the containment pressure above the initial containment pressure of 15.2 psi) was required to meet the NPSH requirements for core spray at rated flow.
Containment overpressure was not required for core spray at runout flow or for two RHR pumps at runout or rated flow. The staff notes that this scenario is different than the one evaluated in the original NRC SE which looked at one core spray and one RHR pump running at atmospheric pressure. This case no longer appears to be the limiting case for NPSH concerns at Duane Arnold.
In addition, new larger capacity strainers were installed during the spring of 1998 and a new containment pressure and temperature response analysis was preformed by GE in support of the new strainers. The staff believes that the new strainers are an improvement to the safety of j
the plant. However, the staff believes, based on our interactions with other utilities with new containment analysis performed by GE, that the new containment analysis did not use the j
same methodology as the containment analysis reviewed and approved during the original
)
licensing of Duane Arnold.
On February 4,1998, DAEC made a presentation to the staff which discussed their resolution of Bulletin 96-03. DAEC's preliminary results indicated that the core spray pumps would require 2.04 psi of containment overpressure at rated flows, while the two RHR pumps would require 3.86 psi at rated flows. This containment overpressure b based on an assumed initial
3-containment pressure of 15.2 psi, not atmospheric pressure. Baced on these preliminary results, the staff believes that an increased reliance on containment overpressure will occur with the change from 1.6 psi to 2.04 psi of containment overpressure for core spray and the change from 0 psi to 3.86 psi of containment overpressure for two RHR pumps at rated flows.
The staff believes that the containment pressure margins discussed in the original NRC SE and Supplement 1 are no longer applicable because of the changes to the NPSH calculations and the new methodology used in the containment pressure and temperature analysis.
Conclusion Any increase in reliance and/or time of the reliance on containment overpressure should be reviewed and approved by the staff. Based on its preliminary review, the staff has concluded that the licensee's proposed resolution of Bulletin 96-03 would increase DAEC's reliar,ce on containment overpressure and would place DAEC in a condition outside its licensing basis.
Therefore, DAEC should request that the staff review and approve its proposal for the resolution to Bulletin 96-03 with respect to the containment overpressure required prior to its implementation.
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