ML082410132

Commitments to Address Degraded Spent Fuel Pool Storage Rack Neutron Absorber

ML082410132
Person / Time
Site:	Palisades
Issue date:	08/27/2008
From:	Schwarz C Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
FOIA/PA-2009-0026
Download: ML082410132 (5)

Text

Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel269 764 2000 August 27,2008 10 CFR 50.4 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Palisades Nuclear Plant Docket 50-255 License No. DPR-20 Commitments to Address Deqraded Spent Fuel Pool Storaae Rack Neutron Absorber

Dear Sir or Madam:

Entergy Nuclear Operations, Inc. (ENO) personnel recently discovered that the Palisades Nuclear Plant region I spent fuel pool storage racks contain less neutron absorber material than assumed in the spent fuel pool criticality analysis of record. This represents a noncompliance with Technical Specification 4.3.1 .I .b. This incident will be reported in accordance with 10 CFR 50.73 in Licensee Event Report 08-004 by September 15, 2008, as a condition prohibited by Technical Specifications. This condition also represents a noncompliance with 10 CFR 50.68. discusses the degraded spent fuel pool neutron absorber material.

To address this condition, E N 0 is implementing actions to ensure that the fuel assemblies within the spent fuel pool continue to remain in a subcritical condition.

Summarv of Commitments

1. E N 0 will prohibit the movement of fuel assemblies within the spent fuel pool that involve positive reac"c'viilychanges until fuel storage requirements in Technical Specifications, 10 CFR 50.68, and the updated final safety analysis report are met.

2. E N 0 will prohibit the movement of fuel assemblies within the spent fuel pool that involve negative reactivity changes until the Nuclear Regulatory Commission has concurred with the planned fuel movement.

3. E N 0 will continue to maintain the spent fuel pool between 75°F and 125°F during normal operation in accordance with plant procedures.

Documen"rontrol Desk Page 2

4. EN0 will maintain spent fuel pool boron concentration greater than 2550 ppm at all limes.

Absent any requested fuel moves, these actions will remain in effect until compliance with requirements in Technical Specification 4.3.1 .I .b, 10 CFR 50.68, and the updated final safety analysis report is established.

I declare under penalty of perjury that the foregoing is true and correct. Executed on August 27,2008.

Christopher J. Schwarz Site Vice President Palisades Nuclear Plant Enclosure CC Administrator, Region Ill, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC

ENCLOSURE 1 DEGRADED SPENT FUEL POOL STORAGE RACK NEUTRON ABSORBER MATERIAL In July 2008, Entergy Nuclear Operations, Inc. (ENO) personnel discovered that the Palisades Nuclear Plant (PNP) region I spent fuel pool storage racks contain less neutron absorber material than assumed in the spent fuel pool criticality analysis of record. This neutron absorber material is relied on to maintain the region 1 spent fuel pool storage racks within the Technical Specification 4.3.1 .1.b criticality requirements.

The Technical Specification reflects credit for the neutron absorber material, rather than soluble boron, in maintaining spent fuel pool criticality within limits.

The degradation of neutron absorption material in region 1 was discovered during "blackness testing." This testing was conducted as a corrective action to assess the effect of previously observed fuel cell wall swelling in region 1 racks on the spent fuel pool criticality analysis. A review of the test data indicated that at least half of the neutron absorber material remains in the racks.

A spent fuel pool criticality operability assessment concluded that, with credit taken for about half of the neutron absorber and a small amount of fuel burnup, a soluble boron concentration of 150 ppm is required to maintain a Meff less than or equal to 0.95 in the region 1 racks based on the most reactive fuel that has been used at the PNP. At the time of discovery, spent fuel pool boron concentration was 2732 ppm and the plant was operating in Mode 1. Technical Specification 4.3.1 .I.b requires that Keff for region 1 fuel racks be less than or equal to 0.95 if fully flooded with unborated water. With soluble boron required to maintain Keff less than or equal to 0.95 in the region 1 fuel racks assuming nominal enrichment, PNP no longer complies with this Technical Specification.

PNP also no longer complies with 10 CFR 50.68(a)(4). This regulation states that, if no credit is taken for soluble boron, Keff must not exceed 0.95 at a 95 percent probability, 95 percent confidence level with maximum fuel assembly reactivity if flooded with unborated water.

Technical Specification 3.7.15 requires that spent fuel pool boron concentration be maintained greater than or equal to 1720 ppm when fuel assemblies are stored in the pool. This is based on crediting soluble boron for the region 2 storage racks. The PNP current licensing basis does not address soluble boron credit for region 1. Therefore, E N 0 considers Technical Specification 3.7.1 5 to be nonconsewative in accordance with Nuclear Regulatory Commission (NRC) Administrative Letter 98-10, "Dispositioning of Technical Specifications That Are insufficient to Assure Plant Safety." E N 0 implemented compensatory measures that included maintaining a boron concentration higher than the minimum required in Technical Specification 3.7.15 until the nonconformance is resolved.

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Immediate Actions The degraded neutron absorber material did not involve an immediate operability concern at the time of discovery because the spent fuel pool boron concentration was 2732 ppm, which was well above the required boron concentration to maintain Keff less than 0.95. In addition, plant procedures required that spent fuel pool boron concentration be maintained at a minimum of 2550 ppm in Modes 1 through 4. In Modes 5 and 6, only 1800 ppm was required. A past operability evaluation confirmed that spent fuel pool boron concentration had been maintained greater than 2550 ppm in recent years.

To address this condition, the following immediate actions were implemented:

1. The movement of fuel assemblies within the spent fuel pool is prohibited.

2. Spent fuel pool boron concentration will be maintained greater than 2550 ppm at -

all times.

Commitments E N 0 recognizes the importance of implementing actions to manage spent fuel pool reactivity and that it is important to communicate planned fuel movements with the NRC until the issue is resolved.

Therefore, E N 0 makes the following commitments:

1. E N 0 will prohibit the movement of fuel assemblies within the spent fuel pool that involve positive reactivity changes until fuel storage requirements in Technical Specifications, 10 CFR 50.68, and the updated final safety analysis report are met.

2. E N 0 will prohibit the movement of fuel assemblies within the spent fuel pool that involve negative reactivity changes until the NRC has concurred with the planned change.

3. E N 0 will continue to maintain the spent fuel pool between 75°F and 125°F during normal operation in accordance with plant procedures.

4. E N 0 will maintain spent fuel pool boron concentration greater than 2550 ppm at all times.

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Corrective Actions E N 0 plans to complete the following actions to resolve the issue:

EN0 is planning a refueling outage in 2009. Due to the commitments in this letter, it will be necessary to request NRC approval for an action to support 2009 refueling outage activities. E N 0 is investigating appropriate restrictions in the spent fuel pool that would apply to these activities, recognizing that the normal NRC review time will not be met.

To support this request, E N 0 is evaluating options that would simplify the NRC review, such as using a restrictive fuel storage pattern or not crediting soluble boron. The following actions are planned:

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