L-MT-05-035, LER 50-004-00 for Monticello Nuclear Generating Plant Regarding Voluntary LER for Control Rod Drive Insert Line Leakage

LER 50-004-00 for Monticello Nuclear Generating Plant Regarding Voluntary LER for Control Rod Drive Insert Line Leakage

ML051320205
Person / Time
Site:	Monticello
Issue date:	05/12/2005
From:	Thomas J. Palmisano Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-05-035 LER 50-004-00
Download: ML051320205 (3)

Text

Monticello Nuclear Generating Plant Operated by Nuclear Management Company, LLC May 12, 2005 L-MT-05-035 10 CFR Part 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Monticello Nuclear Generating Plant Docket No. 50-263 License No. DPR-22 LER 2005-004, - Voluntary LER for Control Rod Drive Insert Line Leakage A Voluntary Licensee Event Report for this occurrence is attached.

This letter makes no new commitments or changes any existing commitments.

Thomas J. Palmisano Site Vice President, Monticello Nuclear Generating Plant Nuclear Management Company, LLC Enclosure cc: Administrator, Region III, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC 2807 West County Road 75

• Monticello, Minnesota 55362-9637 Telephone: 763-295-5151

• Fax: 763-295-1454

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 6-30-2007 (6-2004) COMMISSION Estimated burden per response to comply with this mandatory information collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />.

Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records Management Branch (T-6 E6), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to bjs1@nrc.gov, and to the LICENSEE EVENT REPORT (LER) Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202 (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose information collection (See reverse for required number of does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

digits/characters for each block)

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

Monticello Nuclear Generating Plant 05000263 1 of 2 TITLE (4) Voluntary LER for Control Rod Drive Insert Line Leakage EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR MO DAY YEAR NUMBER NO 05000 FACILITY NAME DOCKET NUMBER 03 09 2005 2005 - 004 - 00 05 12 2005 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) (11)

N MODE (9) 20.2201(b) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)

POWER 20.2201(d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x) 0 LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 73.71(a)(4) 20.2203(a)(2)(i) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(5) 20.2203(a)(2)(ii) 50.36(c)(2) 50.73(a)(2)(v)(B) X OTHER Specify in Abstract below or 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) in NRC Form 366A 20.2203(a)(2)(iv) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) Voluntary 20.2203(a)(2)(v) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(A) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Ron Baumer 763-295-1357 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

MANU- REPORTABLE MANU- REPORTABLE CAUSE SYSTEM COMPONENT CAUSE SYSTEM COMPONENT TO EPIX FACTURER TO EPIX FACTURER B AA PSP No SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION YES (If yes, complete EXPECTED SUBMISSION DATE). X NO DATE (15)

ABSTRACT A voluntary License Event Report is being provided for the following event:

On March 5, 2005 with the Monticello Nuclear Generating plant in a refueling outage, during a scheduled under-vessel walk down, a small water leak was noted on a control rod drive flange. On March 9, Nuclear Management Company (NMC) determined that the leakage was from the top surface of the flange adjacent to the Control Rod Drive (CRD) insert line. The leakage was determined to be active and the result of a flaw in the insert line to CRD flange weld. Metallurgical examination determined that the leak initiated at a small weld void in the weld between the insert line and the CRD housing flange created during original construction. Corrective action taken included performance of a metallurgical, chemical and visual examination of the leaking section of the CRD insert line, replacement of a section of the insert line to re-make the weld at the CRD flange, and a 100 percent visual inspection of the other control rod drive flanges for leakage.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1) DOCKET (2) LER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION Monticello Nuclear Generating Plant 05000263 YEAR NUMBER NUMBER 2 of 2 2005 - 004 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Description On March 5, 2005 with the Monticello Nuclear Generating plant in a refueling outage, during a scheduled primary containment under vessel [RPV] walk down, a small water leak was noted on a control rod drive (CRD) [AA] flange. On March 9, Nuclear Management Company (NMC) determined that the leakage was from the top surface of the flange adjacent to the CRD insert line [PSP]. The leakage was determined to be active and the result of a flaw in the insert line to flange weld. The CRD was isolated to prevent movement and the drive was considered inoperable until the leak was repaired.

A portion of the insert piping was removed for examination and replaced under a station modification.

Following repairs, the CRD was tested and restored to service.

Event Analysis The event was not reportable in accordance with 10 CFR 50.72 or 10 CFR 50.73, however in accordance with NUREG-1022 revision 2, a voluntary Licensee Event Report is being made for this event. The event is not classified as a safety system functional failure.

Safety Significance The safety significance of this issue was low since the CRD was always capable of inserting into the reactor. In the event that the insert line severed at reactor power, the CRD could be inserted by using reactor pressure alone. The safety function of the CRD system would not be affected. The CRD insert lines are not part of the reactor coolant pressure boundary. A risk analysis determined that the effect on the Core Damage Frequency is less than 1 X 10-7 per year. This event had no adverse affect on the health and safety of the pubic.

Cause Metallurgical examination of the pipe determined that the leak was the result of a small weld void in the weld between the insert line and the CRD housing flange created during original construction.

Corrective Action A short section of pipe was removed and replaced under a station modification. A visual inspection of all CRD insert and withdrawal piping connections at the CRD flange was performed and no other leakage was observed.

Failed Component Identification Pipe Manufacturer: Greenville Tubes, Inc (Greenville, PA)

Previous Similar Events A review of the station corrective action program and industry databases found the following similar events: Monticello (LER 1998-03), Brunswick (LER 2-88-007), and Duane Arnold (LER 88-019). Each of these events involved leakage from either the CRD insert or withdrawal lines, however in each case, the leakage was attributed to a corrosion failure mechanism of the pipe. The event discussed in LER 2005-04 was due to a weld void created during original construction.

NRC FORM 366A (1-2001)