ML20052C193
| ML20052C193 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/25/1982 |
| From: | Farmer F EG&G, INC. |
| To: | Scholl R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20052C188 | List: |
| References | |
| CON-FIN-A-6425, TASK-03-10.A, TASK-3-10.A, TASK-RR 0231J, 231J, EGG-EA-5835, NUDOCS 8205040483 | |
| Download: ML20052C193 (8) | |
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EGG-EA-5835 March 1982 SYSTEMATIC EVALUATION PROGRAM, TOPIC III-10.A, THERMAL-0VERLOAD PROTECTION FOR MOTORS OF MOTOR-0PERATED VALVES, BIG ROCK POINT I
F. G. Farmer U.S. Department of Energy Idaho Operations Office
- Idaho National Engineering Laboratory
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N This is an informal report intended for use as a preliminary or working document Prepared for the U.S. Nuclear Regulatory Comission Under DOE Contract No. DE-AC07-761001570 0
FIN No. A6425 g g g g ldaho 8205040483 820430 DR ADOCK 05000
1 hEGsG.....e FORM EG4G 396 INTERIM REPORT Accession No.
Report No.
EGG-EA-5835 C;ntract Program or Project
Title:
Electrical, Instrumentation and Control Systems Support for the Systematic Evaluation Program (II)
Subject of this Document:
Systematic Evaluation Program, Topic III-10.A, Thermal-0verload Protection for Motors of Motor-0perated Valves, Big Rock Point Type of Document:
Informal Report Author (s):
F. G. Farmer Date of Document:
March 1982 R:sponsible NRC Individual and NRC Office or Division:
Ray F. Scholl, Division of Licensing This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes, this document should not be considered final.
EG&G Idaho, Inc.
Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. DE-AC07-761D01570 NRC FIN No.
A6425 l
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0231J SYSTEMATIC EVALUATION PROGRAM TOPIC III-10.A THERMAL-0VERLOAD PROTECTION FOR MOTORS OF MOTOR-0PERATED VALVES BIG ROCK POINT Docket No. 50-155 March 1982 F. G. Farmer EG&G Idaho, Inc.
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ABSTRACT This SEP technical evaluation, for Big Rock Point, reviews the appli-cation of thermal-overload protection devices to motors associated with safety-related motor-operated valves.
FOREWORD This report is supplied as part of the " Electrical, Instrumentation, and Control Systems Support for the Systematic Evaluation Program (II)"
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being conducted for the U.S. Nuclear Regualtory Commission, Office of Nuclear Reactor Regulation, Division of Licensing, by EG8G Idaho, Inc.,
Reliability and Statisitics Branch.
s The U.S. Nuclear Regulatory Commission funded the work under the authorization B&R 20-10-02-05, FIN A6425.
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SYSTEMATIC EVALUATION PROGRAM TOPIC III-10.A THERMAL-0VERLOAD PROTECTION FOR MOTORS OF MOTOR-0PERATED VALVES BIG ROCK P0 INT INTRODUCTION The objective of this review is to provide assurance that the appli-cation of thermal-overload protection devices (TOL) to motors associated with safety-related motor-operated valves (MOV) do not result in needless hindrance of the valves to perform their safety functions.
In accordance with this objective, the application of either one of the two recommendations contained in Regulatory Guide 1.106, " Thermal-Overload Protection for Electric Motors on Motor-0perated Valves," is ade-quate. These recommendations are as follows:
(1) Provided that the completion of the safety function is not jeopardized or that other safety systems are not degraded, (a) the thermal-overload protection devices should be continuously bypassed and temporarily placed in force only when the valve motors are undergoing periodic or maintenance testing, or (b) those thermal-overload protection devices that are normally in force during plant operation should be bypassed under acci-dent conditions.
(2)
The trip setpoint of the thermal-overload protection devices should be established with all uncertainties resolved in favor of completing the safety-related action. With respect to those uncertainties, consider-ation should be given to (a) variations in the ambient temperature at the installed location of the overload protection devices and the valve motors, (b) inaccura-cies in motor heating data and the overload protection device trip characteristics and the matching of these two items, and (c) setpoint drift.
In order to ensure continued functional reliability and the accuracy of the trip point, the thermal-overload protection device should be periodically tested.
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In addition, the current licensing criteria require that:
(3)
In MOV designs that use a torque switch to limit the opening or closing of the valve, the automatic opening or closing signal should be used in conjunction with a corresponding limit switch.
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DISCUSSION Review of Big Rock Point drawing shows 30 motor-operated valves which buses.gp}ied power from diesel-generator-backed or station battery-backed are su None of the DC valves have thermal-overload protection devices.
All of the AC valves (21) have thermal-overload protection devices which are not bypassed. Consumers Power Company has established that TOL trip setpoints are conservatively set in accordance with to Criterion 2, above.8 However, Big Rock Point does not periodically test TOLs, and therefore is not in full compliance with Criterion 2.
Nine M0Vs have automatic open functions which are terminated by either a torque switch or a limit switch (the switches are series-connected with the limit swtch intended to be the primary stop mechanism); the torque switch is bypassed at the start of travel to prevent an over-torque trip during unseating. Two MOVs have automatic close functions which are termi-nated by a torque switch; the torque switch is bypassed by a limit switch at the start of travel.
EVALUATION Thermal-overload protection for motors of motor-operated valves at Big Rock Point meets current licensing criteria with the exception that TOL trip setpoints are not periodically tested.
REFERENCES 1.
IEEE Standard 179-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations."
2.
Branch Technical Position EICSB-27, " Design Criteria for Thermal Over-load Protection for Motors of Motor-0perated Valves."
3.
Regulatory Guide 1.106, " Thermal Overload Protection for Electric Motors on Motor-0perated Valves."
4.
Big Rock Point Drawing E-103, Revision K.
5.
Big Rock Point Drawing E-112, Revision M.
6.
Big Rock Point Drawing E-ll4, Sheet 1, Revision T.
7.
Big Rock Point Drawing E-119, Revision D.
8.
Letter, Consumers Power Company (Vincent) to NRC (Crutchfield), dated February 26, 1982.
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SYSTEMATIC EVALUATION PROGRAM TOPIC III-10. A BIG ROCK POINT TOPIC: III-10. A, Thermal-Overload Protection for Motors of Motor-Operated Valves I.
INTRODUCTION The primary objective of thermal-overload relays is to protect motor windings of motor-operated valves (M0V) against excessive heating. This feature of thermal-overload relays could, however, interfere with the successful functioning of a safety related system.
In nuclear plant safety system application, the ultimate criterion should be to drive the valve to its proper position to mitigate the consequences of an accident, rather than to be concerned with degradation or failure of the motor due to excessive heating.
II.
REVIEW CRITERIA The primary review criteria are:
1.
IEEE Std. 279-1971; and 2.
As a result of numerous operating plant events resulting from torque switch problems the following supplemental criterion was used:
!(3) In M0V designs that use a torque ssitch to limit the opening or closing of the valve, the automatic opening or closing signal should be used in conjuction with a corresponding limit switch."
III.
RELATED SAFETY TOPICS AND INTERFACES There are no safety areas related to the scope of this review that are addressed by other SEP topics nor are any other topics dependent on the results of this review.
IV.
REVIEW GUIDELINES The review should assure that:
(1) thermal-overload protection, if provided, for M0V's should have the trip setpoint at a value high enough to prevent spurious trips due to design inaccuracies, trip setpoint drift, or variation in the ambient temperature at the installed location; (2) the circuits that bypass the thermal-overload protection under accident conditions are designed to IEEE Std. 279-1 971 criteria, as appropriate for the rest of the sdfety related system; and (3) in MOV designs that use a torque switch instead of a limit switch to limit the opening or closing of the valve, the automatic opening or closing signal should be used in cone juction with a corresponding limit switch and thermal-overload should re-l main as backup protection over the first 10% of valve travel.
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EVALUATION
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The design provisions for motor-operated valve protection are described in EG1G Report EGG-EA-5835, " Thermal-Overload Protection for Motors of Motor-Operated Valves."
In summary, Big Rock Point does not meet current licensing criteria because the thermal-overloads are not tested periodically.
VI.
CONCLUSIONS The Big Rock Point designs do not satisfy the current licensing criteria for safety related valve functions. Because the failure of valves due to inadequate protection could lead to the failure of redundant systems, i
the staff proposes that the testing of control systems for safety related valves be modified to include a periodic test or replacement of thermal-overload devices.
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