L-MT-14-057, Response to Requests for Additional Information for the License Amendment Request to Reduce the Reactor Steam Dome Pressure Specified in the Reactor Core Safety Limits

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Response to Requests for Additional Information for the License Amendment Request to Reduce the Reactor Steam Dome Pressure Specified in the Reactor Core Safety Limits
ML14188A249
Person / Time
Site: Monticello Xcel Energy icon.png
Issue date: 07/03/2014
From: Fili K
Northern States Power Co, Xcel Energy
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-14-057, TAC MF1054
Download: ML14188A249 (6)


Text

(l Xcel Energy Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 July 3, 2014 L-MT-14-057 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22 Response to Requests for Additional Information for the License Amendment Request to Reduce the Reactor Steam Dome Pressure Specified in the Reactor Core Safety Limits (TAG No. MF1054)

References:

1) NSPM to NRC, "License Amendment Request: Reduce the Reactor Steam Dome Pressure Specified in the Reactor Core Safety Limits,"

(L-MT-13-01 0) dated March 11, 2013.

2) NRC to NSPM, "Monticello Nuclear Generating Plant- Draft Requests for Additional Information re : Amendment to Reduce Reactor Steam Dome Pressure Safety Limit (TAG No. MF1054)," dated May 27 , 2014.

On March 11, 2013, in accordance with 10 CFR 50.90, the Northern States Power Company- Minnesota (NSPM), doing business as Xcel Energy, Inc., submitted a License Amendment Request (LAR) (Reference 1) proposing to reduce the reactor steam dome pressure specified within Reactor Core Safety Limits Specification 2.1.1, in the Technical Specifications (TSs). This change will resolve a 10 CFR Part 21 condition concerning a potential to momentarily violate Reactor Core Safety Limit 2.1.1.1 during a Pressure Regulator Failure Maximum Demand (Open) transient.

On May 27, 2014, the U.S. Nuclear Regulatory Commission (NRC) requested additional information (RAI) from NSPM (Reference 2) to complete their review. Enclosure 1 provides the requested information.

In accordance with 10 CFR 50.91, a copy of this response, with enclosure, is being provided to the designated Minnesota Official.

Document Control Desk L-MT-14-057 Page 2 of 2 If you have any questions or require additional information, please contact Mr. Richard Loeffler at (763) 295-1247.

Summary of Commitments This letter proposes no new commitments and does not revise any existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on July )' , 2014.

~~J~ ~/-;/-

Karen D. Fili, Site Vice-President, Monticello Nuclear Generating Plant Northern States Power Company- Minnesota Enclosure cc: Regional Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC State of Minnesota

ENCLOSURE 1 MONTICELLO NUCLEAR GENERATING PLANT RESPONSE TO REQUESTS FOR ADDITIONAL INFORMATION FOR THE LICENSE AMENDMENT REQUEST TO REDUCE THE REACTOR STEAM DOME PRESSURE SPECIFIED IN THE REACTOR CORE SAFETY LIMITS (3 Pages Follow)

L-MT-14-057 Enclosure Page 1 of 3 RESPONSE TO REQUESTS FOR ADDITIONAL INFORMATION FOR THE LICENSE AMENDMENT REQUEST TO REDUCE THE REACTOR STEAM DOME PRESSURE SPECIFIED IN THE REACTOR CORE SAFETY LIMITS On May 27, 2014, the U.S. Nuclear Regulatory Commission (NRC) transmitted requests for additional information (RAis) to Northern States Power Company- Minnesota (NSPM). The RAis are provided in italic type with the NSPM responses for each portion of the requests immediately following.

SRXB (Reactor Systems Branch) RAJ# 1 Since the proposed approach for MNGP is a plant-specific resolution of the 10 CFR Part 21 issue as discussed in your submittal (Reference 1), please provide the following additional information:

1. Discuss how Northern States Power Company- Minnesota (NSPM) plans to address the Part 21 issue when the MNGP core may be a mixed-core design consisting of more than one fuel design whose critical power ratio (CPR) correlations have different lower bound pressures.

NSPM Response There are two cases, a transition from one fuel vendor to another, and/or utilizing a fuel design with a different CPR lower bound pressure. The licensee/fuel vendor reload safety analysis process applies in either case.

For a fuel transition, a mixed-core (different vendor fuel designs) will result for several cycles. A license amendment is required for a fuel vendor transition.

For the Monticello AREVA fuel transition, NSPM submitted a license amendment request to adopt the AREVA safety analysis methodology (Reference 2) . As discussed in Enclosure 1, Section 3.4.1 of Reference 2, the proposed AREVA correlations and methodologies will be valid within the proposed safety limits such that any mixed core will be operated within the bounds of an NRC approved methodology. When a fuel design from the same vendor with a different CPR lower bound pressure is to be loaded, the reload safety analysis will again apply. The reload safety analysis process includes identifying various design inputs- including Technical Specification (TS) requirements. The CPR correlations are inherent in the design of the fuel and are considered as part of the reload safety analysis process.

L-MT-13-057 Page 2 of 3

2. Describe the current MNGP core design, including the fuel types in use.

NSPM Response The MNGP reactor core consists of 484 fuel assemblies of [General Electric]

GE14 fuel. The current core design was provided in the Supplemental Reload Licensing Report (SRLR) which was submitted in a letter dated December 20, 2013 (Reference 3) .

When the MNGP core transitions to a fuel design whose lower bound pressure for the CPR correlation is higher (or lower) than that of the current CPR correlation, discuss how NSPM intends to address the change. The discussion should include whether it will require a Technical Specification (TS) license amendment to address the change.

NSPM Response As indicated previously, there are two general cases, a transition from one fuel vendor to another, and/or the utilization of a fuel design with a different CPR lower bound pressure. The licensee/fuel vendor reload safety analysis process as discussed in the response to SRXB RAI # 1 applies in either case.

As long as the lower bound of the fuel's CPR correlation is less than the reactor steam dome pressure specified in the TS Reactor Core Safety Limits (686 psig was specified in the license amendment request (Reference 1) based on the core of GE14 fuel), no TS change is necessary. The AREVA fuel designs CPR correlations (lower bound) are less than the proposed reactor steam dome pressure value. If the fuel design(s) CPR correlation is not less than the TS specified value a license amendment would be necessary.

SRXBRA/#2 In Reference 1, page 2 of 15, it was stated, While this condition had been determined by GE to not involve an actual safety hazard, the potential for violation of a Reactor Core Safety Limit had been identified and restoration to comply with the safety limit is required."

The U.S. Nuclear Regulatory Commission (NRC) staff understands that although this issue may not be an actual safety hazard, by lowering the dome pressure in TS 2.1.1 from the current value of 785 psig to the proposed value of 686 psig may prevent

L-MT-13-057 Page 3 of 3 unnecessary reactor shutdowns as required by TS 2.2.2 if dome pressure goes below 785 psig during a transient.

Please discuss if there are any other operational and/or safety benefits of lowering dome pressure from the current value of 785 psig to 686 psig.

NSPM Response Lowering the value of reactor steam dome pressure in the TS has no physical effect on plant equipment and therefore, no impact on the course of plant transients. The change is an analytical exercise to demonstrate the applicability of correlations and methodologies. There are no known operational or safety benefits.

REFERENCES

1. NSPM to NRC, "License Amendment Request: Reduce the Reactor Steam Dome Pressure Specified in the Reactor Core Safety Limits," (L-MT-13-01 0),

dated March 11, 2013.

2. NSPM to NRC, "License Amendment Request for Transition to AREVA ATRIUM 1OXM Fuel and AREVA Safety Analysis Methodology," (L-MT-13-055), dated July 15, 2013.
3. NSPM to NRC, "Maximum Extended Load Line Limit Analysis Plus: Cycle 27 Safety Reload Licensing Report and Request for Additional Information Response," (L-MT-13-126), dated December 20, 2013. (ADAMS Accession No. ML13358A372)