ML101130510

Record of Conference Call to Convey Verbal Approval of Relief Request No. 18 for Repair of the Standby Liquid Control Tank Leak

ML101130510
Person / Time
Site:	Monticello
Issue date:	04/23/2010
From:	Tam P Plant Licensing Branch III
To:	Loeffler R, Salamon G, Speight S Northern States Power Co
Tam P
References
TAC ME3593
Download: ML101130510 (3)

Text

Accession No. ML101130510 From: Tam, Peter Sent: Friday, April 23, 2010 2:38 PM To: 'Loeffler, Richard A.'; Speight, Steven; Salamon, Gabor Cc: Pascarelli, Robert; Mitchell, Matthew; Purtscher, Patrick; Haeg, Lucas; Riemer, Kenneth; Thomas, Christopher

Subject:

Monticello - Record of conference call conveying verbal approval of Relief Request No. 18 (TAC ME3593)

Rick:

By letter dated April 2, 2010, Northern States Power Company - Minnesota (the licensee) requested NRC approval to implement an alternative (L-MT-10-023) to certain requirements of the 1995 Edition through the 1996 addenda of Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for Monticello Nuclear Generating Station (Monticello). The alternative was requested under the provisions of Title 10 of the Code of Federal Regulations (CFR) 50.55a(a)(3)(i). The proposed alternative is to ASME Code,Section XI, IWC-3120 on Inservice Volumetric and Surface Exams. Under this request, the licensee would be applying ASME Code Case N-705, Evaluation Criteria for Temporary Acceptance of Degradation in Moderate Energy Class 2 or 3 Vessels and Tanks, to evaluate the leakage observed from an ASME Code Class 2 standby liquid control (SLC) tank that operates at atmospheric pressure.

On March 19, 2010, a white, crystalline substance was discovered at the base of SLC tank T-200. The area was reinspected on March 22, 2010, and moisture was present where the white, crystalline substance was previously found. Subsequent nondestructive evaluation (NDE) revealed multiple cracks in the base plate around the circumference of the tank, one of which was longer than the others and served as a path for water to leak out of the SLC tank. The licensee has attributed this leak to transgranular stress corrosion cracking of the base plate (304 stainless steel) of the SLC tank.

The licensees alternative to the stated ASME Code requirement is to apply ASME Code Case N-705 as the evaluation criteria for temporary acceptance of the degradation in the Monticello SLC tank. This Code Case is accepted as part of the Cases of the ASME Boiler and Pressure Vessel Code, but is not yet officially accepted by the NRC. Application of this Code Case requires the licensee to follow the steps outlined below:

1. characterize the degradation and determine that the current condition of the tank or vessel is acceptable,

2. determine if the degradation can be bounded or perform a structural integrity evaluation to calculate a time for the degradation, considering all potential degradation growth mechanisms over the period of evaluation, to reach a maximum acceptable size,

3. monitor conditions daily to ensure leakage/structural integrity does not exceed acceptable limits, and

4. repair/replace the tank or vessel per ASME Code requirements before the degradation reaches the maximum acceptable size or within the prescribed time frame for the

specific situation (not to exceed 26 months from the discovery of the degradation), which ever is less.

The licensee provided information to demonstrate that the proposed alternative would maintain an acceptable level of quality and safety under all licensing basis conditions of operation until the next refueling outage starts in March 2011 (12 months from discovery of the degradation). The NRC staff has considered the submittal on leakage from the T-200 SLC tank at Monticello and concludes that the methodology provided by ASME Code Case N-705 provides an acceptable alternative, because the alternative represents an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i).

The NRC has completed its review of the information provided in the licensees submittal for proposed alternative L-MT-10-023 regarding the use of ASME Code Case N-705. The NRC staff has concluded that the information provided by the licensee is consistent with the provisions of 10 CFR 50.55a(a)(3)(i) and supports the granting of the proposed alternative to ASME Code requirements. Accordingly, following the guidance in NRR Office Instruction LIC-102, "Review of Relief Requests," Rev. 2, the chiefs of the NRCs Vessel and Internals Integrity Branch (CVIB) and the Plant Licensing Branch III-1 (LPL3-1) verbally affirmed the authorization for the licensee to implement the proposed alternative in accordance with the information provided in the licensees letter dated April 2, 2010. The authorization is immediately effective, and will remain in effect until the next refueling outage in March 2011. The NRC staff will follow up in writing in 150 days or less.

NRC participants were:

Robert Pascarelli (LPL3-1, Office of NRR)

Matthew Mitchell (CVIB, Office of NRR)

Peter Tam (LPL3-1, Office of NRR)

Licensee participants were:

T. O'Connor (Site VP),

N. Haskell (Director Site Engineering)

S. Porter (Engineering Programs Manager)

S. Speight (Regulatory Affairs Manager)

G. Sherwood (Supervisor Inspection and Materials)

R. Deopere (Principal Engineering Analyst (ISI Coordinator))

F. Poteet (True North Engineering (ISI Consultant))

R. Loeffler (Senior Licensing Engineer)

Peter S. Tam Senior Project Manager (for Kewaunee and Monticello)

Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Tel. 301-415-1451 E-mail Properties

Mail Envelope Properties ()

Subject:

Monticello - Record of conference call conveying verbal approval of Relief Request No. 18 (TAC ME3593)

Sent Date: 04/23/2010 2:26:32 PM Received Date: 04/23/2010 2:37:00 PM From: Tam, Peter Created By: Peter.Tam@nrc.gov Recipients:

Richard.Loeffler@xenuclear.com ('Loeffler, Richard A.')

Tracking Status: None Steven.Speight@xenuclear.com (Speight, Steven)

Tracking Status: None Gabor.Salamon@xenuclear.com (Salamon, Gabor)

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

Tracking Status: None Matthew.Mitchell@nrc.gov (Mitchell, Matthew)

Tracking Status: None Patrick.Purtscher@nrc.gov (Purtscher, Patrick)

Tracking Status: None Lucas.Haeg@nrc.gov (Haeg, Lucas)

Tracking Status: None Kenneth.Riemer@nrc.gov (Riemer, Kenneth)

Tracking Status: None Christopher.Thomas@nrc.gov (Thomas, Christopher)

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 28907 04/23/2010 Options Expiration Date:

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