Nobody ever answered my question: why did the inaccuracy setpoint failure rate take off in 2009? You have to assume the vibration of the piping on the steamline where the MSSV located is increasing?
Indian Point 2.206: Runaway Main Steam Safety Valve Breakdowns Beginning In 2009
The NRC must have guessed problem was solved with modification. Kinda gutsy move on the NRC's part. Wonder if abnormal degradation was seen in the other valves but not reported. I still think as the vibration damage builds in with these guys it will start not passing their test.NRC 2.206 Response: Junk Safety Valves At Indian PointThe good new is only one valve failed testing and it was one of the few valves without the modifications.
The bad news is it takes from 2011 to fully carry out a component safety modification...its pathetic.
Licensee Event Report# 2016-001-00 Unit 2
On March 4, 2016, during the performance of surveillance procedure 2-PT-R006, Main Steam Safety Valve (MSSV) MS-45B failed to lift within the Technical Specification (TS) as found required range of +/- 3% of the setpoint pressure. Valve MS-45B lifted at 1125 psig, 29 psig outside its acceptance range of 1034 to 1096 psig and 5.7% above its 1065 psig setpoint. The valve was declared inoperable, then subsequently restored to operability upon two successful lifts within the required setpoint range without the need for adjustment. Nine other MSSVs that were tested lifted within the as-found required setpoint range. The apparent cause for the failure was internal friction due to spindle rod wear, which causes the spindle rod to bind against internal components. Corrective actions were modification of MS-45B and twelve other MSSVs, and the replacement of their spindle rods. The event had no effect on public health and safety.
The Energy Industry Identification System Codes are identified within the brackets {}.
DESCRIPTION OF EVENT
This was a dangerous safety component operability determination. They are using incomplete information saying the satisfactory lift pressure test proves the valves capably of doing their safety function. Later valve damage discovered proves the valve was inoperable. The call, the valve was operable, was just not conservative.On March 4, 2016 at 1116 hours, while at approximately 79 percent power, during surveillance testing of the Main Steam Safety Valves (MSSV) in accordance with procedure 2-PT-R006, MSSV MS-45B on Steam Generator (SG) 22 failed to lift within the Technical Specification (TS) as-found required range of+/- 3% of the required setpoint pressure. Valve MS~45B lifted at 1125 psig, 29 psig outside its setpoint range of 1034 to 1096 psig and 5.7% above its 1065 psig setpoint. Consequently, MS-45B was declared inoperable and Technical Specification (TS) 3.7.1 (Main Steam Safety Valves) Condition A was entered. Two immediate subsequent
tests were performed without any adjustments required and the valve lifted at 1038 psig and 1037 psig. With the valve lifting within the required setpoint range, the valve was restored to operability, allowing exit from the TS 3.7.1 Action Statement at 1126 hours. During the surveillance test, nine (9) other MSSVs that were tested passed their as found test criteria and were left within the+/- 1% set point criteria. The failure of MS-45B was recorded in the Indian Point Energy Center (IPEC) Corrective Action Program (CAP) as Condition Report CR-IP2-2016-01204.
During the performance of the 6-year Internal Inspection Preventive Maintenance (PM) activity on MS-45B completed on March 31, 2016 during refueling outage 2R22, numerous dimensions, clearances, and tolerances were verified and internal components were inspected for wear/damage. The valve spindle rod was found to have areas of wear along its length and around the circumference in the form of small steps, which is attributed to system vibration during power operation. All other inspection criteria were satisfactory.There are five code safety valves (MSSVs) and one atmospheric dump valve (ADV) {RV} on each main steam (MS) line outside the Reactor Containment {NH} and upstream of the MS isolation valves {ISV}. The MSSVs consist of four- 6-inch by 10-inch and one 6-inch by 8-inch valve per SG ort each of four MS lines for a total of 20 valves. The five valves 'on each steam line are nominally set to open at 1065, 1080, 1095, 1110, and 1120 psig. The MSSVs are ASME Code relief valves, manufactured by Crosby-Ashton {C710}. Valve MS-45B is a 6-inch by 8-inch Model HA-65W Safety Valve.The apparent cause for the failure was internal friction due to spindle rod wear, which causes the spindle rod to bind against internal components. High vibrations of the spindle rod caused friction between the rod, spring washer, and adjusting bolt. The vibration of the spindle rod while in contact with the spring washer and adjusting bolt resulted in severe wear in the form of steps on the spindle rod. The resulting frictional force occurs on the first lift and then does not repeat.
The vendor's solution to the problem is to install sacrificial bronze wear sleeves along the inner diameter of the spindle rod contact points (inner diameters of the adjusting bolt, upper spring washer, and lower spring washer). The spring washers and adjusting bolt are machined to accept the bronze wear sleeves, which act as a sacrificial metal, preventing spindle wear and step formation. One sleeve is installed in each of the spring washers and two sleeves are installed in the adjusting bolt.
An extent of condition (EOC) was performed to determine where potential conditions with similar valves, design, systems, and environments could occur. The review determined that the EOC found in the failure of MS-45B is restricted to the other 19 MSSVs at Unit 2 and the 20 MSSVs at Unit 3 due to the exclusive 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-setpoint drift. Spring skewing can occur in any of the MSSVs and cause side loading frictional forces which prevent the valve from lifting. Setpoint drift can occur due to age of the components and the operating cycle it is exposed to (e.g., changes in temperature, pressure and vibrations).
PAST SIMILAR EVENTS
A-review was performed of Licensee Event Reports (LERs) for any events rep9rting TS prohibited conditions due to MSSV test failures. LER 2010-002 reported two MSSV failures, one due to valve spring skew and the other due to setpoint drift. LER 2012-005 report~d one MSSV outside the required as-found lift setpoint range due to spring skew/spindle wear.
The MSSVs at Unit 2 are the same as those at Unit 3, and LERs have reported MSSV test failures at Unit 3. LER-2011-004 reported two MSSVs outside the required as found lift setpoint ranges due to spindle wear and spring skew. LER-2013-001 reported two MSSVs outside the required as-found lift setpoint ranges due to galling around the circumference of the spindle rod as a result of vibration for one valve, and internal friction caused by foreign material between the guide bearing and spindle for the other valve. LER 2015-002 reported three MSSVs outside the required as-found lift setpoint ranges due to internal friction from spindle rod vibration.
CORRECTIVE ACTIONS
A modification was initiated in 2011 to install bronze wear sleeves in the upper and lower spring washers and the adjusting bolt as a solution to valve spring skew and spindle wear for the IPEC MSSVs. This modification was completed for 7 of the 20 Unit 2 MSSVs in the 2014 refueling outage (2R21). Valve MS-45B and the 12 other MSSVs that were not modified in 2R21 were modified in the 2016 refueling outage (2R22). New spindles were also installed in these 13 MSSVs in .2R22. All 20 MSSVs have been modified with the bronze wear sleeves.
EVENT ANALYSIS
The event is reportable under 10CFR50.73(a) (2) (i) (B). The licensee shall report any operation or condition which was prohibited by the plant TS. TS 3.7.1 (Main Steam Safety Valves) requires the MSSVs to be operable ·in accordance with TS Tables· 3. 7 .1-1 and 3.7.1-2. The applicable accident/transient analyses require five MSSVs per SG to provide overpressure protection for design basis transients occurring at 102% reactor thermal power. The MSSVs also provide a heat sink for the Reactor Coolant System if the Main Condenser is unavailable and the ADVs cannot relieve steam line pressure.
Operability of the MSSVs is defined as the ability to open within the setpoint range, relieve SG overpressure, and reseat when pressure has been reduced, and is determined by periodic surveillance testing.. TS Surveillance Requirement (SR) 3. 7 .1.1 requires that each MSSV be verified to lift at its required setpoint per Table 3.7.1-2 in accordance with the Inservice Testing Program (IST). On March 4, 2016, MSSV valve MS-45B was found outside its required setpoint range, therefore, it failed its as found testing criteria and was declared inoperable. The valve was disassembled and inspected and determined to have conditions preventing proper operation. 'The apparent cause determined that failure was due to internal friction caused by spindle rod wear from vibration during the operating cycle. Spindle wear is not normal drift, therefore, the valve may have been inoperable during past operation. As it is not possible to determine when the valve would not have lifted within its required setpoint range, the valve was concluded to be inoperable for greater than the TS allowed completion time. An evaluation of applicable accident/transient analyses was performed to determine the impact of one MSSV with a higher opening setpoint. The evaluation concluded the condition would not have resulted in a loss of ·safety function. Therefore, this condition is not reportable under lOCFRSO. 7.3 (a) (2) (v) as a safety system functional failure.
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