ULNRC-05061, Withdrawal of Initial Defense-in-Depth and Diversity Assessment for Digital Upgrade of Callaways Instrumentation and Control Systems
| ML042820203 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 09/24/2004 |
| From: | Keith Young AmerenUE |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-05061 | |
| Download: ML042820203 (4) | |
Text
AmerenUE PO Box 620 Callaway Plant Fulton, MO 65251 September 24, 2004 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Ladies and Gentlemen:
ULNRC-05061 CALLAWAY PLANT 10S F/UNION ELECTRIC CO.
wAmeren DOCKET NUMBER 50-483 UE WITHDRAWAL OF INITIAL DEFENSE-IN-DEPTH AND DIVERSITY IfC ASSESSMENT FOR DIGITAL UPGRADE OF CALLAWAY'S INSTRUMENTATION AND CONTROL SYSTEMS By letter dated March 4, 2004 AmerenUE (Union Electric Company) submitted a defense-in-depth and diversity (D3) assessment for the Framatome Advanced Nuclear Power (FANP) TELEPERM XS (TXS) systems to be installed at the Callaway Plant. In that letter (AmerenUE Letter ULNRC-04945), AmerenUE noted that it was working in conjunction with Wolf Creek Nuclear Operation Corporation (WCNOC) to develop modification plans for replacing current analog-based instrumentation and control systems, including the reactor trip system (RTS) and engineered safety features actuation system (ESFAS) with the digital-based FANP TXS system, for Callaway and Wolf Creek. AmerenUE indicated that it was submitting the D3 assessment for NRC approval because the assessment was intended to support anticipated license amendment requests for the planned system replacements. NRC review and approval of the assessment was requested by December 1, 2004.
The D3 assessment (that was attached to the March 4, 2004 letter) addressed the TXS design generically described in Topical Report EMF-21 10(NP), Revision 1, "TELEPERM XS: A Digital Reactor Protection System," for which the NRC documented its acceptance by letter dated May 5, 2000. The D3 assessment was based on this design but also, in part, on the results of a meeting conducted between AmerenUE, WCNOC, FANP and NRC personnel on November 12, 2003, wherein the defense-in-depth and diversity aspects of the TXS design were discussed, including the potential design to minimize the probability of a software common mode failure. The assessment described the design techniques applied to the TXS design and explained how the application of defense-in-depth and diversity concepts to the both the software and hardware design result in the capability to minimize or tolerate common-mode failures without defeating safety functions.
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a subsidiary of Ameren Corporation
ULNRC05061 September 24, 2004 Page 2 Pursuant to the NRC's guidance in NUREG 0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," Branch Technical Position (BTP) HICB-19, "Guidance for Evaluation of Defense-in-Depth and Diversity in Digital Computer-Based Instrumentation and Control Systems," the D3 assessment included a re-evaluation of the accidents, transients and other events postulated and analyzed in the UFSAR, in order to assess the postulated plant response to these events with the TXS system installed. Due to the TXS system's diversity, however, as enhanced by the proposed design, it was concluded in the assessment that a postulated software common-mode failure would be limited to the extent that credited, automatic RTS and/or ESFAS functions would remain sufficiently available to adequately mitigate all postulated events consistent with the current licensing basis.
Subsequent to submittal of the D3 assessment, however, the NRC staff provided significant comments on the TXS design and D3 assessment in the form of a preliminary position paper. The comments were discussed in a second meeting conducted between AmerenUE, WCNOC, FANP and NRC staff on April 15, 2004.
Based in part on the discussion from the April 15, 2004 meeting, AmerenUE and WCNOC have each determined that the D3 assessment should be revised and that the submitted D3 report should be withdrawn. In addition, the implementation schedule for the TXS modifications at each plant has since been re-evaluated, resulting in postponement of the modifications at each plant. A new assessment(s) will thus be prepared and submitted at a later time. On this basis, AmerenUE requests withdrawal of the D3 assessment that was provided in the March 4, 2004 submittal, such that NRC review and approval of that assessment is no longer required. Please contact me at (573) 676-8659 or Dave Shafer at (314) 554-3104 for any questions you may have concerning this request.
Very truly yours, Ke D. Young Manager, Regulatory Affairs KDY/TBE
ULNRC05061 September 24, 2004 Page 3 cc:
U.S. Nuclear Regulatory Commission (Original and 1 copy)
Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)
Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360
ULNRC0506 1 September 24, 2004 NOTARA*
SEXi STATE OF MISSOUR
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S S COUNTY OF CALLAWAY)
Keith D. Young, of lawful age, being first duly sworn upon oath says that he is Manager, Regulatory Affairs, for Union Electric Company; that he has read the foregoing document and knows the content thereof; that he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief By H
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,47 Kit D. Younk Manager, Regulatory Affairs SUBSCRIBED and sworn to before me this day of J-Yp4t^ ber-, 2004.
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