ML091730389

Emergency LAR RAI

ML091730389
Person / Time
Site:	Clinton
Issue date:	06/22/2009
From:	David M Plant Licensing Branch III
To:	Mathews M Exelon Corp
marshall david 415-1547
References
TAC ME1499
Download: ML091730389 (4)

Text

From: David, Marshall Sent: Monday, June 22, 2009 1:35 PM To: Mitchel.Mathews@exeloncorp.com Cc: Campbell, Stephen; Taylor, Robert; Casto, Greg; Smith, Edward; Blumberg, Mark; Mazumdar, Subinoy; Miranda, Samuel; Lewin, Aron; Cranston, Gregory; Elliott, Robert; Goodwin, Cameron; Ahmed, Iqbal

Subject:

Clinton Emergency LAR RAI (TAC ME1499)

Importance: High

Mitch, As discussed during our conference call just concluded, below is the NRC staff's RAI, to date, on your LAR dated June 15, 2009. Please respond expeditiously and formally to this RAI so that we may continue our review on an emergency basis, as requested in your letter dated June 20, 2009. Please include each staff question followed by your response in your formal RAI response.

Thanks, Marshall

1. By letter dated June 15, 2009, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML0916605802), supplemented by letter dated June 20, 2009, Exelon Generation Company, LLC (EGC), submitted a license amendment request regarding proposed changes to the technical specifications (TSs). The proposed amendment would eliminate the requirement for main steam line isolations on high Turbine Building temperatures from TS Section 3.3.6.1, "Primary Containment and Drywell Isolation Instrumentation," Table 3.3.6 .1-1, (i.e., Function 1.f). The Nuclear Regulatory Commission (NRC) staff is reviewing the submittal and has determined that the following additional information is needed to complete its review.

The proposed changes in the letter dated June 15, 2009, state that No credit is taken in the transient or accident analysis for the automatic isolation of the MSIVs by these Turbine Building area temperature switches. Thus, the Turbine Building temperature switches are not assumed to function to mitigate any accident described in Chapters 6 or 15 of the CPS USAR. However, the purpose of the limiting condition for operation (LCO) for primary containment isolation instrumentation is to satisfy Title 10 of the Code of Federal Regulations (10 CFR) Section 50.36, criterion 2 and 3, which establish, in part, an operating restriction that is an initial condition of a design basis accident (DBA) or a structure which is part of the primary success path and which functions or actuates to mitigate a design basis accident.

The primary containment and drywell isolation instrumentation automatically initiates closure of appropriate primary containment isolation valves (PCIVs) and drywell isolation valves. The function of the PCIVs, in combination with other accident mitigation systems, is to limit fission product release during and following postulated DBAs. Primary containment isolation within the time limits specified for those isolation valves designed to close automatically ensures that the release of radioactive material to the environment will be consistent with the assumptions used in the analyses for a DBA. The proposed changes in the letter dated June 15, 2009 state that

Ambient Temperature-High is provided to detect a leak in the RCPB, and provides diversity to the high flow instrumentation. The isolation occurs when a very small leak has occurred. If the small leak is allowed to continue without isolation, offsite dose limits may be reached. The monitoring of the turbine building temperatures serves to insure a certain level of boundary integrity consistent with that assumed in the licensing bases accident analyses. Levels of leakage from the accident boundary beyond those currently controlled by Function 1.f are not modeled in typical accident analyses. In fact, no leakage is typically assumed, with the exception of MSIV leakage, for SSE (safe shutdown earthquake) qualified pipe and condensers.

Per the USNRC staffs letter entitled, Safety Evaluation Input for Alternative Source Term Full Implementation and Related Technical Specification Changes for Clinton Power Station, Unit 1 (TAC NO. MB8365), dated September 19, 2005 it appears that no leakage, other than MSIV leakage is assumed for the MSIV leakage pathway. For the loss of coolant accident, integrity of piping up to the turbine/auxiliary building (secondary containment) wall is credited. For the control rod drop accident, piping integrity up to and including the condenser is credited.

Please provide a complete assessment of all design basis accidents in the Clinton licensing bases impacted by the proposed change that assume integrity of the MSIV leakage pathway boundary (for example those DBAs that assume the integrity of the MSIV leakage pathway as:

1) an initial condition of a DBA or 2) a structure which is part of the primary success path, or which functions or actuates to mitigate a design basis accident. In the assessment, provide each design basis accident impacted by the proposed change and a justification why the currently assumed level of integrity assumed in the current licensing bases is no longer required.

2. Your letter dated June 15, 2009, states that No credit is taken in the transient or accident analysis for the automatic isolation of the MSIVs by these Turbine Building area temperature switches. Thus, the Turbine Building temperature switches are not assumed to function to mitigate any accident described in Chapters 6 or 15 of the CPS USAR. The letter also states that As stated in the CPS TS Bases, credit is not taken for the Turbine Building temperature instruments in any transient or accident analysis in the USAR, since bounding analyses are performed for large breaks such [as] a MSLBs which are isolated by other MSL leakage detection methods as discussed in Section 3.0. Moreover, this trip is not assumed to mitigate the consequences of a design basis accident (DBA) or transient, and is not input into the assumptions for any DBA analysis.

While the bounding analyses were performed for large breaks, such as a MSLB, the current analyses should bound the spectrum of steam line breaks that extend the boundaries of the MSL. With the deletion of the automatic isolation of the MSIVs by these Turbine Building area temperature switches, justify why the large break MSLB will continue to be limiting and provide an assessment of the spectrum high energy line breaks, as defined by your Updated Final Safety Analysis Report, or justify why such an assessment is not necessary. Provide necessary information so that the DBA can be modeled by the NRC and justification for the assumptions used.

Additional questions:

Are the remaining instruments safety related?

How they are credited to mitigate the consequences of a steam break?

What is the timing of the credited systems?

Are the credited systems automatic or manual?

What is the release from the steam line prior to isolation?

What are the radiological consequences?

3. Please explain the original basis for inclusion of the Turbine Building area temperature switches (used for main steam line isolations on high Turbine Building temperatures from TS Section 3.3.6.1, "Primary Containment and Drywell Isolation Instrumentation," Table 3.3.6 .1-1, (i.e., Function 1.f)) in your current technical specifications and design basis.

4. Your letter dated June 15, 2009, states that if the trip function for the temperature detectors in the Turbine Building main steam tunnel is removed from the Technical Specifications, "an alarm is intended to be maintained to alert the operator in the Control Room of a high temperature condition in the Turbine Building main steam tunnel." Please describe how this alarm will be maintained and used.

E-mail Properties Mail Envelope Properties (01BD2A1885C88F45A12CB413DEF03410ABA0F5E18F)

Subject:

Clinton Emergency LAR RAI (TAC ME1499)

Sent Date: 6/22/2009 1:35:04 PM Received Date: 6/22/2009 1:35:04 PM From: David, Marshall Created By: Marshall.David@nrc.gov Recipients:

Mitchel.Mathews@exeloncorp.com (Mitchel.Mathews@exeloncorp.com)

Tracking Status: None Stephen.Campbell@nrc.gov (Campbell, Stephen)

Tracking Status: None Robert.Taylor@nrc.gov (Taylor, Robert)

Tracking Status: None Greg.Casto@nrc.gov (Casto, Greg)

Tracking Status: None Edward.Smith@nrc.gov (Smith, Edward)

Tracking Status: None Mark.Blumberg@nrc.gov (Blumberg, Mark)

Tracking Status: None Subinoy.Mazumdar@nrc.gov (Mazumdar, Subinoy)

Tracking Status: None Samuel.Miranda@nrc.gov (Miranda, Samuel)

Tracking Status: None Aron.Lewin@nrc.gov (Lewin, Aron)

Tracking Status: None

Gregory.Cranston@nrc.gov (Cranston, Gregory)

Tracking Status: None Robert.Elliott@nrc.gov (Elliott, Robert)

Tracking Status: None Cameron.Goodwin@nrc.gov (Goodwin, Cameron)

Tracking Status: None Iqbal.Ahmed@nrc.gov (Ahmed, Iqbal)

Tracking Status: None Post Office:

HQCLSTR01.nrc.gov Files Size Date & Time MESSAGE 31785 6/22/2009 Options Expiration Date:

Priority: olImportanceHigh ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: