05000266/LER-2016-001

LER-2016-001, Unit 1 Degraded Condition

Point Beach Nuclear Plant Unit 1
Event date:	03-15-2016
Report date:	05-12-2016
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded
2662016001R00 - NRC Website

LER 16-001-00 for Point Beach, Unit 1, Regarding Degraded Condition

ML16133A170
Person / Time
Site:	Point Beach
Issue date:	05/12/2016
From:	McCartney E Point Beach
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC 2016-0019 LER 16-001-00
Download: ML16133A170 (3)

Description of the Event:

At 0649 on March 15, 2016 with Unit 1 shut down in MODE 5 for refueling activities, a boric acid indication upstream of the valve seating surface on the inlet of the valve body of 1CV-200B, Letdown Orifice B Outlet Control Valve was identified as a through-wall flaw. The flaw location was within the reactor coolant system (RCS) pressure boundary as defined by 10 CFR 50.2, "Definitions." The valve body is original plant equipment.

The Unit 1 Letdown Orifice B Outlet Control Valve (1CV-200B) has been replaced and returned to service.

This 60 day licensee event report is being submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(ii)(A) for any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being degraded. The material defect in the primary coolant system could not be found acceptable in accordance with ASME Section XI, IWB-3600, "Analytical Evaluation of Flaws" or ASME Section XI, Table IWB-3410-1, "Acceptance Standards.

Cause of the Event:

The most likely cause of the degraded barrier was localized corrosion near a sand inclusion indication in the valve body.

Analysis of the Event:

Maintenance activities identified a through-wall flaw on the valve body of the Letdown Orifice B Outlet Control Valve. The flaw location was upstream of the valve seating surface, on the inlet of the valve body. 1CV-200B is one of three valves in parallel in the same application. The valve was within the RCS pressure boundary, which is defined as being connected to the RCS, up to and including the outermost containment isolation valve in system piping which penetrates the primary reactor containment. A causal evaluation determined the through-wall flaw in the valve body to most likely be the result of localized corrosion near a sand inclusion indication. The indication was identified during the manufacturing examination and testing processes. The indication was accepted by the manufacturer using the acceptance criteria of ASTM Specification E71, "Reference Radiographs for Steel Casting up to 2 inches in Thickness." The localized corrosion most likely allowed system contents to leech through the sand inclusion. The valve body is original plant equipment and has been in service the entire life of the plant. The flaw has been corrected by replacement of the valve body.

Corrective Actions:

The Unit 1 Letdown Orifice B Outlet Control Valve (1CV-200B) has been replaced and returned to service. Destructive testing will be performed on the removed valve to validate the apparent cause. Additional actions/reviews will be taken as required following receipt of the destructive testing report. Examinations have been completed as part of the extent of condition on three valves from the same heat number that had manufacturing indications. A corrective action has been created to perform a visual examination of one additional valve during the next refueling outage.

Safety Significance:

The event was determined to be of very low safety significance. 1CV-200B can be isolated from the RCS by a remotely operated valve 1RC-427, Reactor Coolant Loop B Cold Leg to Charging and Volume Control System (CVCS) Letdown Isolation Valve. Components with similar sand inclusion indications have been or will be visually examined for evidence of boric acid indications. While the condition was present, there was no loss of any safety systems, structures or components needed to shut down the reactor, maintain safe shutdown conditions, remove residual heat, control the release of radioactive material or mitigate the consequences of an accident. There was no impact on the health and safety of the public as a result of this condition.

Similar Events:

There have not been similar events of this degraded condition in the past three years.

Component Failure Data:

2 INCH-1500 LB COPES-VULCAN MODEL 63 GLOBE VALVE