ML102730785

Summary of September 23, 2010 Conference Call with Duke Regarding Potential License Amendment Request

ML102730785
Person / Time
Site:	Mcguire, McGuire
Issue date:	11/03/2010
From:	Jacqueline Thompson Plant Licensing Branch II
To:
Thompson Jon, NRR/DORL/LPL 2-1, 415-1119
References
TAC ME4655, TAC ME4656
Download: ML102730785 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 3, 2010 DUKE ENERGY CAROLINAS, LLC (DUKE)

FACILITY: MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 (MCGUIRE 1 AND 2)

SUB..IECT:

SUMMARY

OF SEPTEMBER 23, 2010, CONFERENCE CALL WITH DUKE REGARDING POTENTIAL LICENSE AMENDMENT REQUEST (TAC NOS. ME4655 AND ME4656)

On September 23, 2010, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Duke at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was to discuss a potential license amendment request to make changes to the alternate source term (AST) calculations for McGuire 1 and 2. A list of attendees is provided as Enclosure 1.

The licensee presented information (Enclosure 2) which presented a potential precedent for making changes to the current AST analyses for McGuire 1 and 2. The licensee asked questions regarding the basis for the limitation on the use of the ARCHON96 code for source-to receptor distances of less than 10 meters. The NRC staff indicated some of the potential bases for this limitation on the use of the ARCHON96 code.

Members of the public were not in attendance. Public Meeting Feedback forms were not received.

Please direct any inquiries to me at 301-415-1119, or jon.thompson@nrc.gov.

Jon Thompson, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-369 and 50-370

Enclosures:

1. List of Attendees

2. Licensee's Handout cc w/encls: Distribution via Listserv

LIST OF ATTENDEES SEPTEMBER 23,2010, MEETING WITH DUKE ENERGY CAROLINAS, LLC (DUKE)

CONFERENCE CALL TO DISCUSS POTENTIAL LICENSE AMENDMENT REQUEST WITH U.S. NUCLEAR REGULATORY COMMISSION (NRC) STAFF Duke NRC K. Ashe J. Thompson L. Hentz L. Brown N. Keener J. White S. Lanham G. Pi hi C. Huffman M. Costello C. Taylor B. Timm Enclosure 1

Licensee's Handout

[Pre-Submittal Draft LAR Discussion Information from Duke Energy Carolinas, LLC [Duke))

Background

In the McGuire Nuclear Station (MNS) LOCA AST [Alternate Source Term] License Amendment RAI [Request for Additional Information] response letter dated February 12, 2009 ([Agencywide Documents Access and Management System (ADAMS) No. ML090540682]), MNS withdrew several release points from consideration for NRC review and approval to resolve some technical issues including points with a source to receptor distance of less than 10 meters.

Regulatory Guide 1.194 ["Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants"] does not allow the use of the ARCON96 code to calculate an atmospheric dispersion factor (X/a) at a distance less than 10 meters [m]

without a case-by-case review from the NRC.

Some portions of the steam lines at MNS are within 10m of the control room intakes. The minimum distances to the intakes are 7.5 m for the inboard steamlines and 9.5 m for the outboard steam lines. This condition exists on both units. Dispersion factors for these locations are required to analyze the main steam line break (MSLB) accident.

MNS is ready to re-submit the points associated with the MSLB for NRC review and approval for use in the AST dose analysis. MNS has developed a technical justification for using the ARCON96 code for a release point within 7.5 meters from a receptor (control room intake) which is a similar approach to that approved by the NRC in 2005 (Entergy-Waterford 3

[Waterford Steam Electric Station, Unit 3]).

Additional X/a values for MNS will also be submitted. However, the characteristics of those points allow them to be analyzed through the methodologies present in the relevant guidance documents without need for a specific case-by-case discussion. Of these, the MNS doghouse releases attributed to the louver openings will now be conservatively analyzed with a line source instead of an area source per NRC staff discussion during the previous submittal.

Sensitivity Analysis To address this situation Duke intends to present analyses similar to those submitted by Waterford, namely a sensitivity study of ARCON96 behavior for our site specific arrangement and meteorology. The sensitivity analysis will vary the distance between source and receptor along the direction of minimum distance from 100 m down to 1 m. Potential breakpoints along the steamline will also be analyzed to ensure that the minimum distance case is limiting.

An additional sensitivity study will be performed to compare the ARCON96 results with those calculated using the methodology outlined in Section 2.3.4 of the SRP [Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, NUREG 0800]. Specifically, page 2.3.4-8 of the SRP outlines an alternate methodology for estimating X/a for distances less than 10m by using the inverse flow rate (1/F) method. The 1/F results are intended to show that the ARCON96 results are reasonable and conservative. The 1/F results would not be utilized as the licensing basis X/a values. All phases of the accident progression will be modeled including the high velocity blowdown and the relatively low velocity Enclosure 2

-2 primary to secondary leakage through the faulted steam generator until the break flow is analyzed to cease.

Conservatisms Some areas of conservatism that are assumed in the modeling of the MNS MSLB via ARCON96 are the use of a point source to represent the break type of the main steamline and the assumption of neutral buoyancy although the release would be extremely high in energy relative to the surrounding atmosphere. The area of the inboard steamline closest to the VC

[Control Room Area Ventilation System] intakes is a straight run of pipe which has no features that would make it more likely to fail than the remainder of steamline piping in the yard at MNS.

From a probabilistic standpoint, the section of piping which is less than 10 meters from the VC intake represents a relatively small portion of the possible points for a break to occur in the main steamline piping. Also, adjacent building area input to ARCON96 will be effectively set to zero to ensure conservatism since the effect on X/Q is inversely proportional to building area.

It is understood that this proposed analysis methodology would not be assumed to bound any other potential release points less than 10 meters from a receptor and that should any other points of this nature be identified they would require their own case-by-case review.

Similar Licensing Approach Waterford (Entergy) submitted an AST LAR [License Amendment Request] (7/15/2004) which included a release point at 6.6 m. Waterford received approval on 3/29/2005 ([ADAMS Accession No. ML050890248]). In addressing x/Qs, the original LAR references a response to RAls from their concurrent request for an extended power uprate dated 3/4/2004 ([ADAMS Accession No. ML040690028]).

In the 3/4/2004 EPU [Extended Power Uprate] RAls (Q2 and Response, pages 37,38 of 48),

Waterford justified the use of ARCON96 for an ADV [Atmospheric Dump Valve] release point 6.6 m from the control room intake based on the following:

A comparison of the 6.6 m x/Q to the 10m X/Q in the same direction with reasonable results Stating that flow velocity of a release from the ADV is ignored Stating ARCON96 "allows for the calculation of X/Q values for distances from 0 to 100 m and does not specify any restrictions for the calculation of X/Q values for distances under 10m."

In the SE [Safety Evaluation] (pp. 26, 27) approving the Waterford methods the NRC stated:

liThe east ADV is less than 10 ms from the east intake. RG 1.194 states that such situations should be addressed on a case-by-case basis. Therefore, the licensee performed sensitivity comparisons of resultant X/Q values at a range of distances using ARCON96, estimated plume rise (for which they had not taken credit in their estimates) using RG 1.194, estimated mixing of the effluent with steam and air prior to release from the ADV, and provided a description of several other conservatisms in the dose assessment. The licensee noted that the volumetric

-3 magnitude as the X/O value calculated for the 0 to 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> time period using the ARCON96 computer code. The staff reviewed the information provided by the licensee and finds the magnitude of the X/O values for the east ADV to the east control room air intake acceptable for this specific case. However, the staff does not approve the use of the ARCON96 code at distances less than about 10 ms without adequate case-specific justification."

November 3, 2010 LICENSEE: DUKE ENERGY CAROLINAS, LLC (DUKE)

FACILITY: MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 (MCGUIRE 1 AND 2)

SUB"IECT:

SUMMARY

OF SEPTEMBER 23, 2010, CONFERENCE CALL WITH DUKE REGARDING POTENTIAL LICENSE AMENDMENT REQUEST (TAC NOS. ME4655 AND ME4656)

On September 23, 2010, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Duke at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was to discuss a potential license amendment request to make changes to the alternate source term (AST) calculations for McGuire 1 and 2. A list of attendees is provided as Enclosure 1.

The licensee presented information (Enclosure 2) which presented a potential precedent for making changes to the current AST analyses for McGuire 1 and 2. The licensee asked questions regarding the basis for the limitation on the use of the ARCHON96 code for source-to receptor distances of less than 10 meters. The NRC staff indicated some of the potential bases for this limitation on the use of the ARCHON96 code.

Members of the public were not in attendance. Public Meeting Feedback forms were not received.

Please direct any inquiries to me at 301-415-1119, or jon.thompson@nrc.gov.

IRA!

Jon Thompson, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-369 and 50-370

Enclosures:

1. List of Attendees

2. Licensee's Handout cc w/encls: Distribution via Listserv DISTRIBUTION:

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