Safety Valves In Our Nuclear Power Plants Going Wild

Licensee Event Report # 2015-002-01, "Technical Specification Prohibited Condition Caused by Four Main Steam Safety Valves Outside Their As- Found Lift Set Point Test Acceptance Criteria"

Indian Point Unit No. 3

Docket No. 50-286
 

Reference: 1. LER-2015-002-00 submitted by letter NL-15-065 dated April 27, 2015

An extent of condition (EOC) was performed to determine where potential conditions with similar valves and environments could occur. The review determined that EOC round in the failure of MSSV MS-45-4, MS-46-2 and MS-47-4 is restricted to the other 17 MSSVs at unit 3 and the 20 MSSVs at unit 2 due to the valve design. All MSSVs are exposed to high vibrations during their operating cycle during which wear can occur. Previous failures of MSSVs have included wear due to spring skewing and set point…

Why is Entergy having so many problems with Safety Relief Valves and now the Main Steam Safety Valves? The MSSV provide overpressure protection in the main steam lines. 

If I hear fretting or normal main steam line vibrations damaging these valve again I am going to vomit.

Why can’t the engineers design this valves for the duty and conditions of the plant? They just sit there doing nothing for 99.99% of the time.
 

For only three years below, this is shocking. So how have the failure changed in the last decade... is less testing and maintenance behind this.

A review was performed of Licensee Event Reports (LERs) for the past three years for any events reporting TS prohibited conditions due to multiple valve test failures. LER-2011-004 reported two MSSV's outside their as-found lift set point acceptance criteria due to spindle wear and spring skew. LER-2013-001 reported two MSSVs (MS-46-3 and MS-48-3) outside their as-found set point acceptance criteria. The cause of MS-46-3 failure was galling around the circumference of the spindle rod as a result of vibration. MS-48-3 evidenced similar fretting on one side of the spindle consistent with what was found on valve MS-46-3. Failure cause was determined to be due to internal friction caused by foreign material between the guide bearing and spindle. The causes for the previous events reported in LER-2011-004 are similar to this event.

Recent issues with fretting and normal vibration issues with SRVs and MNSSV include the following plants:

Hatch

Oyster Creek (yellow finding)

Dresden
 

Quad Cities
 

Pilgrim

These valves are failing because the vendor can’t control the component dimensional or material conditions in the valves. These are equivalent to the valves that gave us TMI.
  

I am amazed pre-plant testing haven’t picked up the weaknesses of these valves. Pre-plant testing either can't pick up the defect or the testing damages the fragile valves:) 

I am shocked the manufacturers don’t provide completely durable and bullet proof components and valve to these nuclear power plants? Just to be clear, the MSSV come from PWRs and the SRVs comes from BWRs.

You get it, Indian Point don’t trust the safety of their valves, don’t understand the degradation mechanism, talking about “another” valve design…they are testing these valves twice as frequently now because they don't understand the degradation mechanisms.

LER 2011-004-00 plus two other LERs in 10 years...

During the Preventive Maintenance (PM) of both valves, run-out and wear along the radius of the spindles were noted. In a high flow system, the result would be increased wear along the spindle in the form of steps which were found with MS-47-4 and MS-48-4.

It is a runaway train, in defective component these identical problems happen over and over without fixing the problem. These plants are great at churning paperwork...poor a fixing problems so they never show up again.

LER 2009-002-000: Over and over again, half ass fixes for at least 6 years...the runaway degradation occurring unabated at least since 2009. 

Spindle problems, who cares indeterminate and this seems to be the beginning of this problem. What changed before 2009?   

Cause of Event

The apparent cause of the two MSSVs lifting greater than 3% of their nominal setpoint is indeterminate but most likely caused by setpoint drift. MS-45-1 and MS-48-3 were disassembled and inspected and identified to have some scoring on their valve spindles. Assessment with Original Equipment Manufacturer (OEM) could not directly relate the indications discovered on the valves' spindles to the As-Found test results