IR 05000341/1988011

Insp Rept 50-341/88-11 on 880328-30.No Violations or Deviations Noted.Major Areas Inspected:Activities Re Main Steam Isolation Valve Spring Failures & IE Bulletin 85-003 Concerning motor-operated Valve Switch Settings

ML20151P512
Person / Time
Site:	Fermi
Issue date:	04/15/1988
From:	Danielson D, James Smith NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20151P476	List: IR 05000341/1988011 ML20151P472
References
50-341-88-11, IEB-85-003, IEB-85-3, NUDOCS 8804260183
Download: ML20151P512 (8)

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, .. U.S. NUCLEAR REGULATORY COMMISSION

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REGION III

Report No.- 50-341/88011(DRS)

Docket No. 50-341 License No. NPF-43 Licensee: The Detroit Edison Company 2000 Second Avenue-Detroit, MI 48224 Facility Name: Fermi 2 Inspection At: Fermi Site, Monroe, Michigan Inspection Conducted: March 28-30, 1988 Inspector: , $h 4hf//6 Date Approved By: D. H. Danielson, Chief / /P Materials and Processes Date Section

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Inspection Summary Inspection on March'28-30, 1988 (Report No. 50-341/88011(DRS))

Areas Inspected: Special, unannounced inspection of licensee activities with respect to main steam isolation valve spring failures (92700).and IE Bulletin 85-03 regarding motor-operated valve switch settings (25573).

Results: No violations or deviations were identified.

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DETAILS 1. Persons Contacted Detroit Edison Company (DECO)

• S. Catola,-Vice President, Nuclear Engineering

• D. Gipson, Plant Manager

• L. Goodman, Licensing Supervisor

• L. Fron, Supervisor, Mechanics / Fluids

• G. Lane, Lead Maintenance Support. Technician

• J. Pendergrast, Associate Compliance Engineer

• A. Lim, Nuclear Engineer

• R. Lenart, General Director, Nuclear Engineering

• J. Melito, Nuclear Engineer

• R. May, Superintendent, Maintenance and Modifications

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• Stafford, Director, Nuclear QA and Plant Security P. Anthony, Licensing F. Owens, Maintenance Foreman U. S. Nuclear Regulatory Commission (NRC)

• Rogers, Senior Resident Inspector

• Denotes those attending the exit meeting held March 30, 1988, at the Fermi Sit . (Closed) Main Steam Isolation Valve Spring Failures (LER 86011)

During April 1986 when investigating valve leakage problems, the licensee discovered the failure of four Main Steam Isolation Valve (MSIV)

springs on two valves. The springs are part of a sixteen spring system used to assist valve closure for each valve. The licensee evaluated the safety implications of the spring failures and determined that the impact was minimal. This conclusion was based on the large number of springs available to assist closure and on the fact that a safety-related air supply is available for MSIV closur The spring failure event was reported on May 28, 1986, in LER 86-11-0 In that LER, the licensee indicated that quench cracking and embrittlement

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due to improper heat treatment and tempering were the cause of the spring failures. These springs are AISI 5160 material and were provided with the valves from Attwood & Morrill (A&M). The springs were purchased by A&M from Duer Spring (A&M Purchase Order No. AM5243, Heat No. 8067703, Oven No. 20224-R5, test report dated January 6, 1972). Two of the broken inner springs and three non-failed inner springs were submitted to the Detroit Edison Engineering Research Division (DER) for metallurgical i examination. From their investigation, DER concluded that the root cause I of the spring failure (Heat No. 8067703) was three-fold in nature: (1)

p temper embrittlement; (2) quench cracking; and (3) surface imperfections.

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Details of the spring manufacturing process and of the tests and analyses performed to resolve the spring failure problem are provided in NRC Inspection Report No. 50-341/87022. During a telephone conference on July 9,1987, the licensee's staff indicated that they intended to replace all currently installed valve springs in early 1988 during a shutdown for valve leak rate testing. The licensee's staff also stated that all replacement springs will be:

Tes te'd ~ hringconstan Magnetic particle tested after heat treatment and before paintin Compression tested to the solid conditio Also, 13 spare inner springs and 13 spare outer springs were to be ordered with the replacement springs and compression cycled 5,000 times each (over ten times the design number) to assure the quality of the spring As indicated in NRC Inspection Report No. 50-341/87022, the completion of these proposed activities appears fully adequate to resolve any question concerning the quality of the valve spring The NRC inspector observed work in progress on the MSIV's. Spring replacement was complete on three outboard valves and in progress on the fourth. All original springs were removed from the four inboard valves and installation of the replacement springs had not begun. The original springs are temporarily stored in case additional analysis is require Although all replacement springs were reported to be on site, only those needed for in-process work were available for viewing in the work are A conditional release was necessary for the inner springs because the 5000 cycle test was not completed when they were needed for assembly of the MSIV' The conditional release allows the springs to be installed in the valves but prevents the valves from being declared operable until the test is completed and a full release is give Technical data for the replacement springs and for acceptance tests on the springs are provided in the following table:

Fermi ? Main Steam Isolation Spring Data Characteristic Outer Spring Inner Spring

Purchase Order Number NM 165874 NM 165873

Source Atwood & Morrill A&M/Duer (A&E)/Duer Material AISI 5160 AISI 5160 Part Number 33135-416-3219-921 33134-824-3219-921

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Nondestructive Magnetic Particle - Magnetic Particle -

' Examination (NDE) Wet Fluorescent Wet Fluorescent-(After heat treatment, (all 77 springs (all 77 springs but before painting tested) tested)

with' red oxide paint)

5000 Cycle Operation Test -

Sprinas Involved 13 springs from 13 springs from (no further use this' order (new) this order (new)

planned for these 3 springs from 3 springs from springs after prior * order (old) prior * order (old)

test)

Test Population (#1) 8 new springs (#1) 8 new springs Groups (#2) 5 new and 3 old (#2) 5 new and 3 old springs springs Height of Free 234" 23" Spring (approx.)

Test Range: Closed: Closed:

17"-1150# 16 3/4"-618#

Open: Open:

101"-2360# 101"-1260#

Test Frequency 3 cycles / minute 3 cycles / minute (Approx.) (Approx.)

Post-Test NDE Visual Examination Visual Examination for Failure for Failure Tests Performed On Springs For Use in MSIVs Springs Involved 64 new 64 new Measure Initial 231"(Approx.) 23"(Approx.)

Free Height Compress to Solid 91"(Approx.) 8 3/16"(Approx. )

Height Measure Final 231(Approx.) 23(Approx.)

Free Height Measure load at 1150# 0 17" 618# 0 16 3/4" Closed Height (Load A)**

Measure Load at 2360# 0 101" 1260# 0 101 Open Height (Load 8)**

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I Post Test NDE Visual Examination Visual Examination for Failure for Failure Apply Red 0xide Paint Paint Paint

• Springs from prior order were not from the lot which exhibited failures. Their performance is not pertinent to test results. They were provided only to fill required spaces during test **For spring constant 3. Licensee Action on IE Bulletins (0 pea) IE Bulletin (IEB) 85-03: Motor Operated Valve (MOV) Common Mode Failure During Plant Transients Due to Improper Switch setting The analysis and adjusting of switd. setting on motor operated valves was in progress during thi;. WRC inspecticn but this work was interrupted because of equipment problems. As a result of the work interruption, the performance of work could not be witnessed by the NRC inspector. However, the response of the licensee to related problems was assessed through review of the following recent Deviation Event Reports (DER): (DER 88-0447, dated March 10,1988) Grease in spring pack causing hydraulic lockup: During MOVATS testing of four valves, a shift in shutdown torque was detected with repeated operation. When the valve operators were opened, the grease was found to be separated and some of the more liquid portion was found inside the spring pac The licensee indicated that no spring pack at Fermi was ever found to be filled with grease or completely "locked" so that rapid compression was impossible. The effect noted at Fermi is one of a limited penetration of lubricant into the spring pack. The lubricant tends to "damp" compression rather than stop i The damping action of the grease requires a greater force to compress the spring pack a given amount. The torque switch responds to axial compression of the spring pack. When a greater force is required to overcome hydraulic resistance to that motion, greater torque must be applied to the operator to provide the same linear compression of the spring. This damping action can increase the value of the torque at which the motor is shut off without changing the setting of the torque switch. In the event of a complete lockup (never seen at Fermi), the motor could be stalled without activating the torque switc The licensee-proposed mechanism by which grease separation contributes to this problem is that the more mobile portion of the separated grease forms a puddle on the surface of the heavier grecs )

There it is picked up by the gears of the valve operator. The rapidly rotating gears in the operator of a fast-acting valve throw the more mobile lubricant off to coat the inside of the operator,

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including the spring pack. As the spring pack flexes, it aspirate This action tends to bring some of the lubricant inside the spring pack. If the ability to draw in lubricant exceeds that to expel it, the lubricant in the spring pack will increase until equilibrium is reached. The licensee feels that the solution of this problem is in the changing of grease in all fast acting valves before separation takes place. To implement this solution, all 25 fast acting valves (of which the four in this DER are members) will have grease removed and replace The NRC inspector concluded from his review of the DER that the evidence in this problem does not conclusively identify any causative mechanism. The mechanism proposed by the licensee is feasible and origina The applied solution has particular merit in that it introduces no untried techniques or materials. The licensee indicated that a schedule for future inspectinn for grease separation has not been identified but is anticipated before the DER is closed, b. (DER-0468, dated March 12,1988) Motor Operator Exceeding Rated Capacity: During MOVATS testing of a valve, the as-found thrusts exceeded the rating of the operator (14,000 lbs.). The opening thrust was 15,536 lbs. and closing thrust was 24,202 lbs. The as-found setting met the specification requirements in effect when it was last set. The excessive thrust resulted from a high stem factor loss assumption. The valve manufacturer was consulted about the possible damage resulting from this overthrusting and indicated no concern. The operator manufacturer indicated that overthrusting of this magnitude would justify a complete disassembly of the operator and the following examinations:

(1) Visually inspect ball bearings and races for evidence of

"brinnelling."

(2) Perform NDE of case, cap, and boltin (Method was not speci fied. )

All prescribed NDE and visual examinations were performed with no rejectable deficiencies. M0 VATS testing was completed with valve settings within specified limit The licensee was prudent in seeking the advice of the valve and operator manufacturers, c. (DER 88-0469, dated March 12,1988) Defective Spring Pack Cartridge On Motor Operator: During MOVATS testing, a spring pack cartridge in a valve operator was found to be unable to perform within the limits provided by Limitorque. The spring pack was replaced. The defective spring pack was examined and found to contain flattened spring elements. The licensee tentatively believes that the spring deformation resulted from being held too long in the compressed condition. Further examination of this spring pack is anticipated but undefined. All other valves likely to be subject to this problem will be M0 VATS tested during this outag ,

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u The NRC inspector considers the response of the licensee to this problem was appropriate and adequate. Metallurgical analysis of the deformed spring elements might better define the problem as to whether it is service or manufacture based, but consideration of future analysis was not complete at the time of the NRC inspection, d. (DER 88-534, dated March 20,1988) Possible Grease Separation In Limitorque: When the cover was removed from the limit switch compartment on a valve operator, an oily substance was found on the wires, walls, and floor of the compartment. The licensee attributes the presence of the oily substance in the compartment to grease separation in the adjacent gear compartment. The lighter and more mobile constituent of the grease is more likely to achieve access to the limit switch compartment than the heavier grease could because it is can pass more readily through the wall penetrations provided for rotating shaft The NRC inspector considers the rationale for the licensee's analysis of this problem to plausible although it does not explain the mechanism by which the oil is spread about the limit switch compartment. The solution applied by the licensee is to change the grease in this operato This entails no new work because this action was already in process for this and other similar valves as a result of corrective action for DER 88-0447. The corrective action appears to be appropriate for the proposed source of the prehle e. (DER 88-0592) dated March 26,19881 Limitorque Motor Operator Overthrust: The drive housing cap of a motor operated valve generator was found to have two broken bolts and two bent bolts. The operator was dismantled and subjected to visual examination and nondestructive examination in accordance with the manufacturer recommendations. Visual examination disclosed damage to the bearings on the worn / torque spring assembly. The licensee indicated that additional work is planned on this M0V although it was not formally recorded at the time of the inspection. That work includes the calculation of the overthrust force necessary to cause failure of the operator drive housing cap bolts. When this force is determined, the value of the force will be transmitted to the valve manufacturer and his recommendations for corrective action will be sought. After reassembly, the valve will be checked manually for existing torque and limit settings to determine if the overthrust was the result of equipment fa' lure, improper switch settings, or inadequate procedures controlling switch setting. Appropriate corrective action will be determined depending on the results of this investigatio The NRC inspector considers the licensee's response to this problem to be adequate and commensurate with the significance of the problem identified and the generic implications of the problem. All safety-related MOVs in the plant will be MOVATs tested before the end of the current outag s . .

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4. Exit Meeting i

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The Region III inspector met with the licensee representatives (denoted '

in Paragraph 1) at the conclusion of the inspection on March 30, 198 The inspector summarized the scope and findings of the inspection and discussed the likely informational content of the inspection report with regard to documents or processes reviewed during the inspection. The licensee did not identify any such documents or processes as proprietary.

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