ML20236S010
| ML20236S010 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/16/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20236R998 | List: |
| References | |
| NUDOCS 8711240167 | |
| Download: ML20236S010 (2) | |
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1 ENCLOSURE 2 SAFETY EVALUATION FOR THE OFFICE OF NUCLEAR REACTOR REGULATION NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.
l MILLSTONE NUCLEAR POWER STATION, UNIT NO. 3 DOCKET NO. 50-423
1.0 INTRODUCTION
I By letter dated November 20, 1984, Northeast Nuclear Energy Company, the licensee for Millstone Unit 3 (Millstone 3), (a four loop Westinghouse plant with loop isolation valves) requested approval to operate the unit with one loop isolated and out-of-service (three loop operation) in the event of an j
equipment failure in that loop.
Further information covering three loop i
operation was provided in an August 25, 1986 letter from the licensee.
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2.0 DISCUSSION
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During three loop operation several control indicators, annunciators and i
channel trip lights will be in abnomal conditions based on the status of the isolated loop. The licensee plans to use tags or stickers to identify these j
abnomal indications.
In order to complete the human factors engineering review of the licensee's method of identifying indicators and annunciators and 1
their impact upon plant procedures and operator training the staff requested additional infomation to be submitted by Northeast Utilities (NU) by letter dated January 21, 1987. A meeting was held on February 12, 1987 to discuss the staff's request.
Subsequently, a meeting was conducted at the Millstone 3 site on February 25, 1987 to review and discuss the impact on three loop operation on the control boards in the control room.
When one loop is taken out of service, various parameters and plant conditions are affected.
For example, the protection system must be modified since the inactive loop will be isolated from the primary coolant system by closed isolation valves in the hot and cold legs. The concern of the staff is that the control room instrumentation and displays will be different in the three j
loop mode and this might provide the operators with information which might be misleading.
The staff reviewed the steps taken by Millstone 3 to ensure that the information presented to the operator is valid and will not mislead or confuse him.
In letters dated February 20, 1987, and March 18, 1987 the licensee submitted the responses which were needed to complete the human factors engineering review.
3.0 EVALUATION The licensee submitted a list of instruments associated with the " loop out of service" which will be in an abnormal status.
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A unique stick-on label identifier will be prominently attached to the displays of the isolated loop to remind the operator of the status of the loop. Utilization of this identifier is controlled by a three loop operating procedure.
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Isolated locp indicators will net be failed but will shcw the actual values of the paranster in the isolated loop. For example, DELTA T will show zero because there is no flow, and steam generator level will shcw 100% level.
The I&C surveillance procedures will provide for re-scaling of any affected instrument loops if system operating ranges change because of the three loop operation, such that normal operating zones on meters are no longer applicable, or values are different from what appear in procedures; therefore, the operator is not presented with conflicting information on displays for the operating locps.
Input from the isolated loop instrumentation to the annunciator is defeated to maintain the operability of the alarrr function. Annunciator winc'cws that are asscciated with the isolated loop components will net be identified with a special "out-of-service" tag. The affected reactor coolant pump annunciators and system loop parameters for the isolated loop are disabled thrcugh 'wo key i
lock switches. The status of the affected protection system bistable stcfus lights is verified as a part of the I&C surveillance. A unique stick-on label identifier is placed on the affected displays.
i By procedures, training and technical specifications, the operators are made aware of conditiens that will be different during three loop operation. For l
example, the DELTA T will indicate higher value in three loop operation than four loop operation.
The staff concludes that the three loop operation does not appear to cause any safety concerns from a human factors point of view. However, the staff during the site visit (February 1987) cbserved that the Millstone 3 operators are not trained on three loop operation. A training program for operating the plant on three loops should be provided and the operators should be properly treined prior to entering this mode of operation.
Dated: MOV 161987 Principal Contributor:
S. M. Saba
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