ML13337A289

NRR E-mail Capture - Monticello Nuclear Generating Plant - Draft Request for Additional Information Maximum Extended Load Line Limit Analysis Plus LAR Review

ML13337A289
Person / Time
Site:	Monticello
Issue date:	11/26/2013
From:	Beltz T Plant Licensing Branch III
To:	Fields J Northern States Power Co
References
Download: ML13337A289 (3)

Text

NRR-PMDAPEm Resource From: Beltz, Terry Sent: Tuesday, November 26, 2013 5:34 AM To: Fields, John S.

Cc: Eckholt, Gene F. (Eugene.Eckholt@xenuclear.com); Jackson, Christopher; Carlson, Robert; Stattel, Richard; Rahn, David; Huang, Tai

Subject:

Monticello Nuclear Generating Plant - Draft Request for Additional Information re: Maximum Extended Load Line Limit Analysis Plus LAR Review (TAC No. ME3145)

Attachments: Monticello Nuclear Generating Plant - Request for Additional Information (EICB) - MELLLA+

LAR.docx

Dear Mr. Fields:

By letter dated January 21, 2010 (Agencywide Documents Access and Management System Accession No. ML100280558), Northern States Power Company-Minnesota (the licensee), submitted a license amendment request (LAR) for the Monticello Nuclear Generating Plant (MNGP) Renewed Operating License and Technical Specifications. The proposed change would allow operation in the expanded Maximum Extended Load line Limit Analysis Plus (MELLLA+) domain. MNGP is currently licensed to operate in the MELLLA domain and with thermal-hydraulic stability Option III.

The U.S. Nuclear Regulatory Commission staff in the Instrumentation and Controls Branch of the Office of Nuclear Reactor Regulation has identified an area where additional information is needed to complete the staffs MELLLA+ LAR review. The draft request for additional information (RAIs) is attached.

You may request to discuss the contents of the RAI with the NRC staff in a conference call. Otherwise, please accept this RAI as formal Request for Additional Information and respond to the question by December 27, 2013.

Please let me know if you have any questions or concerns.

Sincerely, Terry A. Beltz, Senior Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation (301) 415-3049 Terry.Beltz@nrc.gov 1

Hearing Identifier: NRR_PMDA Email Number: 937 Mail Envelope Properties (Terry.Beltz@nrc.gov20131126053400)

Subject:

Monticello Nuclear Generating Plant - Draft Request for Additional Information re:

Maximum Extended Load Line Limit Analysis Plus LAR Review (TAC No. ME3145)

Sent Date: 11/26/2013 5:34:21 AM Received Date: 11/26/2013 5:34:00 AM From: Beltz, Terry Created By: Terry.Beltz@nrc.gov Recipients:

"Eckholt, Gene F. (Eugene.Eckholt@xenuclear.com)" <Eugene.Eckholt@xenuclear.com>

Tracking Status: None "Jackson, Christopher" <Christopher.Jackson@nrc.gov>

Tracking Status: None "Carlson, Robert" <Robert.Carlson@nrc.gov>

Tracking Status: None "Stattel, Richard" <Richard.Stattel@nrc.gov>

Tracking Status: None "Rahn, David" <David.Rahn@nrc.gov>

Tracking Status: None "Huang, Tai" <Tai.Huang@nrc.gov>

Tracking Status: None "Fields, John S." <John.Fields@xenuclear.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 1416 11/26/2013 5:34:00 AM Monticello Nuclear Generating Plant - Request for Additional Information (EICB) - MELLLA+ LAR.docx 25209 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE MONTICELLO NUCLEAR GENERATING PLANT LICENSE AMENDMENT REQUEST FOR MAXIMUM EXTENDED LOAD LINE LIMIT ANALYSIS PLUS (MELLLA+)

NORTHERN STATES POWER COMPANY, INC.

DOCKET NO. 50-263 (TAC NO. ME3145)

The use of common software for normal and backup stability can lead to a condition where both functions could become disabled due to a common-cause software failure. Thus, the U.S.

Nuclear Regulatory Commission (NRC) staff requests the following supplemental information:

The NRC Staff Requirements Memorandum (SRM) on SECY-93-087 (ADAMS Accession No. ML003708056), dated July 21, 1993, describes the position of NRC regarding Diversity and Defense-In-Depth (D3). This SRM states that applicants using digital or computer based technology shall assess the defense-in-depth and diversity of the proposed instrumentation and control system to demonstrate that vulnerabilities to common mode failures have been adequately addressed. The SRM also states: in performing the assessment, the vendor or applicant shall analyze each postulated common-mode failure for each event that is evaluated in the accident analysis section of the safety analysis report (SAR) using best estimate methods. The vendor or applicant shall demonstrate adequate diversity within the design for each of these events.

The NRC staff notes that the OPRM DSS-CD safety function is credited in the Monticello USAR Chapter 14, Plant Safety Analysis, for mitigation of a plant instability event. This event is analyzed in Section 14.6, Plant Stability Analysis, of the Monticello USAR. It remains apparent that a postulated common-mode failure of the NUMAC OPRM could disable the safety trip function performed by the DSS-CD algorithms. Therefore, a diverse means of performing either the same function (Reactor Trip) or a different function is required.

Please identify what this diverse means is (i.e. High Reactor Pressure Trip, Manual Operator Action, or ATWS) and provide a documented basis that the diverse means is unlikely to be subject to the same common-mode failure that would disable the DSS-CD safety function.