ML20042F197

LER 90-002-00:on 900402,main Steam Safety Valve 1-MS-2013 Failed to Relieve Setpoint During Tech Spec Testing.Caused by Personnel Error During Setpoint Adjustment.Safety Valves 1-MS-2011,1-MS-2006 & 1-MS-2008 restored.W/900502 Ltr

ML20042F197
Person / Time
Site:	Point Beach
Issue date:	05/02/1990
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-90-039, CON-NRC-90-39 LER-90-002, LER-90-2, VPNPD-90-205, NUDOCS 9005070374
Download: ML20042F197 (7)

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U. S. NUCLEAR REGULATORY COMMISSION '

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LICENSEE EVENT REPORT' 90-002-00 .j MAIN STEAM SAFETY VALVE 1-MS-2013.

.SETPOINT NONCONSERVATIVE )

POINT BEACH NUCLEAR PLANT. UNIT 1

't Enclosed.is Licensee Event Report 90-002-00 for~ Point-Beach Nuclear Plant. Unit 1. This report'is provided in-accordance with 10 ' CFR 50.73 (a) (2) (1)', "Any operation or condition  !

prohibited by the Plant's Technical Specifications." 7 This report details the failure of a Main Steam Safety \'alve 1- , ,

MS-2013. '

M If any further information is required, please contact us.

- I Very truly,yours, e 7 C.

Y W..Fy/

Vice President '

Nuclear Power:

Enclosure f Copies to NRC Regional Administrator, Region III [

NRC Resident Inspector s 9005070374'900502 '7 .

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""S o i i rv.e,,i, .,i. - ... . . - n, Main on Steam April Safety 2, 1990, Valveduring 1-MS-2013 Technical failed Specification to relieve at testing, a setpo int defined by ASME Code Section III (105% of steam generator design), s The valve relieved at test pressures of 1260 psig (116%) and i 1235 psig (115%).

Technical Specification 15.3.4.A.1 indicates "a minimum of eight s main steam safety valves be available" . . . when the primary plant is heated above 350'F. The non-conservative setpoint of valve '

1-MS-2013 left the A steam generator with less than total overpressure relief.

Investigations by plant maintenance and the valve maintenance consultant could find no anomalies. Evidence indicates the setpoint may have been out of specification since the last valve refurbishment which occurred in May 1986. Per Technical 9 specifications, two additional safety valves were tested and the l results were acceptable.

This report is filed pursuant to 10 CFR 50.73 (a) (2) (i), "Any operation or condition prohibited by the plant's Technical ~

Specifications."

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Main Steam Safety Valve 1-MS 2013 is a 6 inch, high capacity nozzle type relief valve, style SR 10 HC-65W, manufactured by Crosby Valve and Gage Co., of Wrentham, Massachusetts. Spring compression maintains the valve closed aaainst normal system pressure. The spring compression can be ad3usted to. alter the relief setpoint.

When the pressure in the valve inlet reaches the setpoint, the valve will open with very little simmer or warning. The valve will continue to relieve until pressure under the valve decreases; at which time the valve will close sharply.

The safety relief valve is located on a branch header from the A main steam line/A steam generator. The header and valves are immediately outside of the containment structure in the Unit 1 containment facade.

Valve 1-MS-2013 is one of four identical safety relief valves located on the branch header along with a 6 inch air operated

" atmospheric steam dump" valve. Each of the reliefs is sized with a relief capacity of 833,000 lbs/hr, or approximately 25% of the total full power steam flow from one steam generator. The atmospheric steam dump has a relief capacity of 333,400 lbs/hr or approximately '

10% flow from one steam generator. The design setpoint for relief valve 1-MS-2013 is 1125 psig, which is 103.6% of the stt a generator design pressure (1085 psig). The remaining valves in the A branch  !

header are set as follows:

1-MS-2010 1085 psig  !

1-MS-2011 1100 psig l 1-MS-2012 1125 psig 1-MS-2016 1050 psig (atmospheric steam dump) i The system design was the result of 1965 Code requirements of ASME Section III. The requirements indicated that safety valve capacity must prevent the vessel (steam generator) from exceeding 100% of the  !

design pressure. One valve must be set at the design pressure. '

The others (when multiple valves are used) may be set up to, but no greater that 105% of the ' design (with a setpoint variance of less than 1%). The code requirements of 1965 ASME VIII, sections UG-125 arv essentially the same.

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00 ol3 or o je, TEXT U more wece 4 soeusm,. wee sacteew pc ,stm NEA b (In Since 1985, Wisconsin Electric Power company has been obligated by the Wisconsin Administrative Code, to secure the services of an lent certified by the National Board with a VR and NR stamp, W omplete safety valve repairs. In 1986 all eight Unit 1 safety relief valves were sent to the certified repair agent (Crane Services) for testing, refurbishment and setpoint adjustments.

After a setpoint adjustment was made, the agent attached a seal to the nozzle ring set screw, the adjusting ring set screw and cap set screw.

The nozzle and adjusting set screw seals were broken to check the setting of the rings in 1987 on MS 2005, 2007, 2010, 2011, 2012, &

2013 because we found the rings on the two valves being tested that .

year (2006 & 2008) mispositioned. Resetting of the nozzle and adjusting rings does not have any impact on the setpoint of the valve.

EVENT DESCRIPTIONS:

On March 31, 1990, Unit 1 was shut down for annual refueling and maintenance outage 17. On April 2, plant maintenance mechanics commenced Routine Maintenance Procedure #55 Main Steam Safety Valve Setpoint Test. Since the five year safety valve program began its cycle in 1986, safety valves 1-MS-2013 and 1-MS-2011 were the last pair of valves scheduled for test. The set screw seals installed by the certified repair agent in 1986 and 1987 were-inspected and found to be in place. Each valve was connected to the test rig per procedure. Test results for safety valve 1-MS-2011 were found to be within specification.

During the first test of safety valve 1-MS-2013, the valve actuated at 1260 psig. During the second test, the valve actuated at 1235 psig. Both tests indicated the setpoint of the valve to be out of specification - high (non-conservative).

After the setpoint discrepancies were discovered by plant l

maintenance mechanics, the valve was sent to the certified safety valve repairer, Crane Services of Romeoville, :llinois. Test summaries by Crane Services confirmed tests completed by plant maintenance personnel (average setpoint test of 1211 psig). The I test results differed slightly based on the use of steam as a pressure medium vice the use of nitrogen by plant maintenance mechanics.

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This Licensee Event Report is filed pursuant to 10 CFR 50.73(a) (2)

(i), "any operation or condition pnhibited by the plant's Technical Specifications." The NRC resident was notified. In this case one of eight main steam safety valve was discovered with a non-conservative sotpoint. This violates Technical Specification 15.3.4.A.1 "A minimum of eight (8) main steam safety valve available" . . . when reactor coolant is above 350*F.

The Energy Industry Identification System component function identifier and system name, of the valve and system referred to in this LER are:

PBNP Valve Identifier 1-MS-2013 EII system SB EII component RV CAUSES:

After the setpoint discrepancies were discovered by plant maintenance mechanics, the valve was sent to the certified safety valve repairer, Crane Services of Romeoville, Illinois. Test summaries by Crane Services-confirmed tests completed by plant maintenance personnel (average setpoint test of 1211 psig). The test results differed slightly based on the use of steam as a pressure medium vice the use of nitrogen by plant maintenance mechanics.

l The " Disassembly As-Found Condition Report" indicated:

1. No wear marks on the spindle or inside'the compression screw.

2. No unusual signs.of any misalignment in the body' guide area or the body-to-bonnet mating surfaces.

3. No problem in either adjusting rings.

In summary, "no unusual discrepancies were found." With the I absence of hardware and procedural problems, it is suspected that i there was a personnel error when the setpoint adjustment was made by Crane Services in May of 1986. This theory is substantiated i

further by the fact that the valve seals installed in 1986 and L 1987, were intact when the tests began on April 2, 1990. The error. 1 may have been the result of a faulty gauge or incorrect reading at '

the time of refurbishment.

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Main steam safety valve 1-MS-2013 has been an exceptionally reliable component. In its nineteen years of operation the valve seats were lapped twice to correct minor steam leakage: April 1973 and May 1986. Previous tests of this valve have been within specification. A review of maintenance history of the safety valves (16 total) of both units indicated only routine repairs and occasional refurbishments (preventive maintenance). This is the first documented occurrence of a non-conservative failure of a main steam safety relief valve at Point Beach.

In addition, substantial evidence suggests that the non-conservative setpoint resulted from a personnel error by the certified valve repair agent and not from a hardware or procedural problem. In summary, there appears to be no industry nor plant generic problems with regard to the non-conservative setpoint of main steam safety valve 1-MS-2013.

CORRECTIVE ACTIONS:

Four types of corrective action were implemente,d.

1. Two additional safety valves were tested (1-MS-2006 and 1-MS-2008) in accordance with Technical Specifications and ASME Section XI, IW-3 513. The results of the additional tests were acceptab)e.

2. Safety valve 1-MS-2013 was sent to Crane Services for analysis and repairs. The setpoint was adjusted, the valve was recertified and restored to service.

3. Safety valves 1-MS-2011, 1-MS-2006 and 1-MS-2008 were  !

inspected, recertified and restored to operation.

4. Annual retests of the valves refurbished by Crane Services in 1986 were reviewed. Each test was within specification and found to be acceptable.

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SAFETY ANALYSIS:

The safety implications of this setpoint discrepancy are nominal.

The other th"eo safety valves were eperable and the setpoint was only 105% {1260/(1085[1.05 + .01])) above that allowed by code.

Should a main steam safety valve fail non-conservatively, two steam line (system) ruptures could be postulated: one inside of containment and one outside of containment. The Final Safety Analysis Report Section 14.2.5 considers both of these events along with :

- a coincidental steam generator tube rupture

- a ninimum shutdown margin equal to 2.77%

- the most negative moderator temperature coefficient for the rodded core at the end of life

- the rod having the most reactivity stuck in its fully withdrawn position and

- one safety injection pump failure The steam release results in an initial increase in steam flow t which decreases during the accident as the steam pressure falls, The energy removal from the reactor coolant system causes a reduction of coolant temperature and pressure. With a negative moderator temperature coefficient, the cooldown results in a reduction of core shutdown margin. If the most reactive control rod is ansumed stuck in its fully withdrawn position, there.is a possibility that the core will become critical and return to power with the remaining control rods inserted. Assuming the most pessimistic combination of circumstances which could lead to power generation following a steam line break, the core is ultimately shut down by the boric acid in the Safety Injection System.

If operators maintain steam system integrity, steam relief +

nability can be afforded via the:

-1. Atmospheric Steam Dump Valves (10% total steam load rejection),

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2. Condenser Steam Dump System (40% total steam load rejection). I 4

In summary, it is felt the health and safety of the general public l and plant employees was not at risk during this event.  !

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