IR 05000483/1987022

Insp Rept 50-483/87-22 on 870714-17.No Violations Noted. Major Areas Inspected:Ie Bulletin 85-003, Motor-Operated Valve Failures During Plant Transients Due to Improper Switch Settings

ML20237K585
Person / Time
Site:	Callaway
Issue date:	08/20/1987
From:	Phillips M, Wohld P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20237K569	List: IR 05000483/1987022 ML20237K566
References
50-483-87-22, IEB-85-003, IEB-85-3, NUDOCS 8708270223
Download: ML20237K585 (6)

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s U.S. NUCLEAR REGULATORY COMMISSION

REGION III

Report No. 50-483/87022(DRS)

Docket No. 50-483 License No, NPF-30 Licensee: The Union Electric Company Post Office Box 149 St. Louis, MD 63166 Facility Name: Callaway, Unit 1 Inspection At,: . Callaway Site, Callaway County, Missouri Inspection Conducted: ' July 14-17,1987 Inspector R o d O/@

Date j Approved By P ips, Chief 8/20M7 Operational Programs Date

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'!nspectior. Summary Inspection on July 14-17, 1987 (Report No. 50-483/87022(DRS))

' Areas Inspected: Special safety inspection of the licensee's activities with respect to Inspection and Enforcement Bulletin No. 85-03, " Motor-0perated ,

Valve Failures During Plant Transients Due to Improper' Switch Settings."

Resultsl No violations were identified, j i

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8708270223 870821 PDR ADOCM 05000403 G PDR

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DETAILS

1. Persons Contacted Union Electric Company

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i J. D. Blosser, Plant Manager  !

S. M. Bond, Assistant Engineer j S. T. Ganz, QA~ Engineer '

J. C. Gearhart, Superintendent, QA 4 P. W. Godt, QA Engineer W. R. Robinson, Assistant Manager, Operations and Maintenance G. J. Roesner, Assistant Engineer ,

C. E. Slizewski, Supervising Engineer, Technical Support ]

W. A. Witt, Supervising Engineer j U. S. Nuclear Reculatory Commission B. h. Little, Senior Resident Inspctor 2. IE Bulletin Followup (0 pen) IEB 85-03: Motor-Operated Valve (MOV) Cnmmon Mode Failure 1 During Plant Transients Due to Improper Switch Setting "

Callaway has been considered the lead plant in terms of a possible, generically acceptable response to this bulletin. Inspector review 1 of the response revealed three major items of concern; however, only )

one was applicable to the actual program being implemented by Union Electric. The overall program being implemented on site, withstanding l

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the need for some additional development, appeared generally satisfactor Additional inspection of the program and observation of testing is planned before closure of the bulleti During this initial inspection, in addition to reviewing the licensee's bulletin response, the inspector reviewed drawings, procedures, and engineering records; discussed the valve test program being implemented; reviewed test data; and received additional documents for further review and discussion. The detailed inspection findings are addressed I below: I Bulletin Response Dated March 5, 1987 Three major items of concern resulted from a review of this response: )

(1) The response indicated that for gate valves the stroke distance between the onset of stem motion and disk loading would be less than one percent. This is simply not true, making the three percent bypass of the open torque switch, as discussed in the response, inadequate and unacceptable. The licensee understood

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j the inspector's comments and indicated that it had been their i J

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intent to present the " valve cracking. peak" as having a )

one percent. width. Fortunately, Union Electric had not {

adopted the three percent bypass philosophy, as written 1 in the response, in implementing its valve program and, l hence, this was not a concern at Callawa (2) The closure thrust equation presented in.the response under predicts the closure thrust that was actually measured on the Velan gate valves at Davis-Besse for which Bulletin No. 85-03 '

was written. While this was a concern, the_ response also indicated that very little confidence existed in using this equation on gate valves at that time and it was known to be inadequate for many of the Westinghouse gate valves. On discussing this, the Callaway staff indicated that the closure thrust equation was not being used for any of the " bulletin" gate valves, and, that all the bulletin valves would receive both open and closing differential pressure (dp) tests (except for approximately five small Velan globe valves) with instrumentation and recording of. valve stroke diagnostic information. Hence, the inspection findings indicated that Union Electric was adopting a quality test program without dependence on the closure thrust equation for gate valve (3) Testing to assure that valve packing was not over tightened has neither been adequately addressed in the bulletin response nor in valve programs implemented onsite. In responding to a question in this area, Union' Electric indicated that stroke timing, per the ASME Code,Section XI, would be the post maintenance test applied when packing was tightened. However, on reviewing a typical sample of the Alternating Current (AC)

valve motor " speed vs. torque" curves for the bulletin valves, a simple calculation showed that an increase in motor running load from rated to twice rated would result in only a three percent change in stroke time. This. change, because of undervoltage considerations, represents approximately 30 percent of the operator capability (at undervoltage) and 30 percent of the operator capability as normally limited by the torque switch at its upper limi The code requirements do not begin to address stroke time changes even close to three percent; hence, it is technically inappropriate to consider using the code for operability testing of these AC valves. To depend on stroke timing for operability testing, per the ASME. Code, appears to be contrary to:

(1 the basic single failure criterion for plant design; (2 Criterion XI, Test Control, in Appendix B of 10 CFR Part 50; (3 Criterion XVI, Corrective Action, in Appendix B of 10 CFR Part 50; (4) Generic Letter 83-28 which requires appropriate post maintenance testing; and (5) IE Bulletin No. 85-03 with its associated requirements for motor-operated valve _ _ _ _ ----_________--

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The inspector discussed a number of alternatives, either readily available or reasonably easily developed, that would address this area. This is considered an unresolved item pending further consideration by Union Electric and I

evaluation by NRC into the applicability of the above regulations to this concern (483/87022-01(DRS)).

b. Valve Operator Elementary Wiring Diagram Review and Valve Logic Evaluation A review of the elementary wiring diagrams for the bulletin valves indicated the following:

General - The valve logic was clearly presented and showed a basically i siiuliif,~ electrical logic design for the valves. The use of spuial

,eatures.that complicates the electrical logic was avoided in the dusig Thermal Overloads - Thermal overloads were not used at Callawa The licensee indicated that the duty cycle was observed during testing of sensitive valves. The inspector recommended that the >

licensee (1) review the adequacy of controls in this area, and (2) consider using already installed thermal overload relay contacts to provide an alarm functio Open Logic - Callaway used the typical "open on limit" logic for all the rising stern valves. Open torque switches were used on some valves (not all) with the typical torque switch bypas While the bypass was inadequately prescribed in the past, it was being reset for 20 to 25 percent of valve disk motion in response to the bulletin and the torque switch was being set at a conservatively high value. (The open thrust provided at the torque switch trip would also be recorded and verified using diagnostic equipment. For those valves without an open torque switch, the open torque switch and open torque switch bypass settings were not a consideration).

Backseating - The licensee had adopted an open limit switch setting at 90% open and had adopted testing to assure that backseating was not occurring after the switch was set (for rising stem valves only).

Valve Closure Indication - Typical valve design in the past was to use contacts from the same limit switch rotor (Rotor No. 2) both for " valve closed" indication and for the open torque switch bypas Since the Limitorque operators at Callaway are all "four rotor" models, Union Electric was separating the two functions to separate '

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rotors where the bypass setting conflicted with accurate valve position indicatio i Closure Logic - All rising stem valves closed either entirely on the close torque switch or on a close limit switch; a torque switch bypass was not used. To assure that the torque switch (where used)

was set high enough and that all the valve operators provided adequate thrust, M0 VATS, Inc. diagnostic equipment would be used. Since past

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historical data was, in most cases, inadequate to reliably predict L closure thrust requirements, Union Electric would be diagnostic testing most of the bulletin valves at maximum available differential pressur The inspector noted during the valve logic review that Westinghouse valves with SB and SBD model operators had been designed to "close on limit" without using the closure torque switch at all. The close limit switch was set baced on compression of the Belleville compensating spring assembly in the drive train which limited the ultimate thrust imparted to the valve stem. The licensee indicated that this "close on limit" design was the result of corrective action for problems identified with Westinghouse Electro-Motive Division (EMD) valves, the subject of an earlier IE Bulletin (No. 81-02).

c. Undervoltage Capability '

The Callaway valves have to be tested by the vendor at 80 percent voltage and engineering records indicated that this minimum voltage had been analyzed to be available at the valve motor both for start and stall torque conditions of the valves, thereby assuring that the minimum torque requirements from the valve operator motor would be me d. Program Implementation The licensee's intended program appeared generally adequate as planned, with some exceptions as noted herein, and no problems were identified with activities already performed. The licensee's staff had scheduled additional valve training and was continuing to develop their vahe program. The following items needed additional development by the licensee or NRC review, or both:

(1) Procedural changes were needed to better develop and document valve testing analyses and evaluations. The licensee indicated that this was planned and that plots of the as left diagnostic signatures for each valve would be made available for inspector revie (2) Long term, followup testing needed additional developmen The inspector recommended (a) that Union Electric consider auxiliary feedwater and safety injection valve differential pressure testing to commence periodically with check valve full flow testing already in place, and (b) that the valve signature data be retained for long term comparison evaluations and that I test data be compared against realistic valve expectations in I order to better monitor and trend valve performanc e. Data Review Test data and evaluations were not readily available to revie Further, much of the testing remained to be done; hence, additional inspection and evaluation of test results will be necessary in the

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-future. _Some' data was reviewed on a computer monitor and discussed 1

'with the licensee. No problems other than the accessibility of the -

data for review were note Additional Actions' Required

.To close the bulletin,' additional program development by Union Electric was necessary; testing remained to be completed and a final report was required. Additional inspection planned by Region III

'would include test observations and evaluation of the data. Further evaluation of the program and procedures was also planned, i i

3 .- Unresolved Items I

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Unresolved items are matters about which more information is' required- d in order to ascertain whether they are acceptable items, items of noncompliance, or deviations. An unresolved item disclosed during

'the inspection is discussed in Paragraph 2.a.(3).

.] Exit Interview .

The inspector met with licensee representatives (denoted in Paragraph 1)

on July 17, 1987,-'to discuss the scope and findings of the. inspectio .

The licensee acknowledged the statements made by the' inspector with respect to items discussed in'the report. The inspector also discussed "

the likely informational' content of the inspection. report with: regard to documents or processes reviewed by the inspector during.this inspectio The licensee did not . identify any- such documents / processes as proprietar ~

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