ML20203G536

Safety Evaluation Supporting Util Responses to Generic Ltr 83-28,Item 1.2 Re post-trip Review Data & Info Capability

ML20203G536
Person / Time
Site:	Wolf Creek
Issue date:	07/24/1986
From:	NRC
To:
Shared Package
ML20203G534	List: ML20203G529 ML20203G536
References
GL-83-28, TAC-57387, NUDOCS 8608010296
Download: ML20203G536 (10)

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ENCLOSURE 1 SAFETY EVALUATION REPORT FOR GENERIC LETTER 83-28, ITEM 1.2 - POST-TRIP REVIEW -

(DATA AND INFORMATION CAPARILITY)

WOLF CREEK GENERATING STATION DOCKET NOS. 50-482 I. INTRODUCTION On February 25, 1983, both of the scram circuit breakers at Unit 1 of the Salem Nuclear Power Plant (SNPP) failed to open upon an automatic reactor trip signal from the reactor protection system. This incident occurred during the plant start-up and the reactor was tripped manually by the operator about 30 seconds after the initiation of the automatic trip signal. The failure of the circuit breakers has been determined to be related to the sticking of the undervoltage trip attachment. On February 22, 1983, during start-uo of SNPP, Unit 1, an automatic trip signal occurred as the result of steam generator low-low level. In this case, the reactor was tripped manually by the operator almost coincidentally with the automatic trip. Following these incidents, on February 28, 1983, the NRC Executive Director for Operations (E00) directed the staff to investigate and report on the generic implications of these occurrences. The results of the staff's inquiry into these incidents are re-ported in NUREG-1000 " Generic Implications of ATWS Events at the Salem Nuclear Power Plant." As a result of this investigation, the Commission requested (by Generic Letter 83-28 dated July 8, 1983) all licensees of operating reactors, applicants for an operating license, and holders of construction permits to respond to certain generic concerns. These concerns are categorized into four areas: (1) Post-Trip Review, (2) Equipment Classification and Vendor Interface, (3) Post-Maintenance Testing, and (4) Reactor Trip System Reliability Improve- l ments.

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The first action item, Post-Trip Review, consists of Action Item 1.1, " Program Descriotion and Procedure" and Action Item 1.2, " Data and Information Capability." This safety evaluation report (SER) addresses Action Item 1.2 only.

II. REVIEW GUIDELINES The following review guidelines were developed after initial evaluation of the various utility responses to Item 1.2 of Generic Letter 83-28 and incorporate the best features of these submittals. As such, these review guidelines in effect represent a " good practices" approach to post-trip review. We have re-viewed the licensee's response to Item 1.2 against these guidelines:

A. The equipment that provides the digital sequence of events (SOE) record and the analog time history records of an unscheduled shutdown should provide a reliable source of the necessary information to be used in the post-trip review. Each plant variable which is necessary to determine the cause and progression of the events following a plant trip should be monitored by at least one recorder (such as a sequence-of-events recorder or a plant process computer) for digital parameters; and strip charts, a plant process computer or analog recorder for analog (time history) variables. Performance characteristics guidelines for SOE and time history recorders are as follows:

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o Each sequence of events recorder should be capable of detectinq and recording the sequence of events with a sufficient time discrimination capability to ensure that the time responses associated with each monitored safety-related system can be ascertained, and that a determination can be made as to whether the time response is within acceptable limits based on FSAR Chapter 15 Accident Analyses. The recommended guidelines for the SOE time discrimination is approximately 100 milliseconds. If current SOE recorders do not have this time discrimination capability the licensee should show that the current time discrimination capability is sufficient for an adequate reconstruction of the course of the reactor trip and post-trip events. As a minimum this should include the ability to adequately reconstruct the tra'nsient and accident scenarios presented in Chapter 15 of the plant FSAR.

o Each analog time history data recorder should have a sample interval small enough so that the incident can be accurately reconstructed following a reactor trip. As a minimum, the licensee should be able to reconstruct the course of the transient and accident sequences evaluated in the accident

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analysis of Chapter 15 of the plant FSAR. The recommended guideline for the sample interval is 10 seconds. If the time history equipment does not meet this guideline, the licensee should show that the time history capability is sufficient to accurately reconstruct the transient and accident sequences presented in Chapter 15 of the FSAR. To support the post-trip analysis of the cause of the trip and the proper functinning of involved safety related equipment, each analog time history data j recorder should be capable of updating and retaining information from approximately five minutes prior to the trip until at least ten minutes after the trip.

o All equipment used to record sequence of events and time history i

information should be powef5d from a reliable and non-interruptible power source. The power source used need not be Class 1E.

B. The sequence of events and time history recording equipment should monitor sufficient digital and analog parameters, respectively, to assura that the course of the reactor trip and post-trip events can be reconstructed. The parameters monitored should provide sufficient information to determine

! the root cause of the unscheduled shutdown, the progression of the reactor trip, and the response of the plant parameters and protection and safety systems to the unscheduled shutdowns. Specifically, all input parameters i

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associated with reactor trips, safety injections and other safety-related systems as well as output parameters sufficient to record the proper functioning of these systems should be recorded for use in the post-trip review. The parameters deemed necessary, as a minimum, to perform a post-trip review that would determine if the plant remained within its safety limit design envelope are presented in Table 1. They were selected on the basis of staff engineering judgment following a complete evaluation of utility submittals. If the Itcensee's SOE recorders and time history recorders do not monitor all of the parameters suggested in these tables the licensee should show that the existing set of monitored oarameters are sufficient to establish that the plant remained within the design envelone for the accident conditions analyzed in Chapter 15 of the plant FSAR.

C. The information gathered by the sequence of events and time history recorders should be stored in a manner that will allow for data retrieval and analysis. The data may be retained in either hardcopy, (e.g., com-puter printout, strip chart record), or in an accessible memory (e.a.,

maanetic disc or tape). This information should be presented in a read-able and meaningful format, taking into consideration good human factors practices such as those outlined in NUREG-0700.

D. Retention of data from all unscheduled shutdowns provides a valuable reference source for the determination of the acceptability of the plant vital parameter and equipment response to subsequent unscheduled shutdowns. Information gathered during the post-trip review is to be retained for the life of the plant for post-trip review comparisons of subsequent events.

III. EVALUATION AND CONCLUSION By letters dated November 15, 1983, February 29, 1984, and December 6, 1985, Kansas Gas and Electric provided information regarding its post-trip review pro-gram data and information capabilities for Wolf Creek Generatino Station. We have evaluated the licensee's submittals against the review guidelines described in Section II. A brief description of the licensee's responses and the staff's evaluation of the response against each of the review quidelines follows:

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The licensee has described the performance characteristics of the equipment used to record the sequence of events and time history data needed for post-trip review. Based on our review of the licensee's submittals, we find that the seouence of events recorder and time history characteristics conform to the guidelines described in Section II A, and are acceptable.

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8. The licensee has established and identified the parameters to be monitored and recorded for post-trip review. Based on our review, we find that the parameters selected by the licensee include all of those identified in Table 1 and conform to the guidelines described in Section II B and therefore are acceptable.

C. The licensee described the means for storage and retrieval of the information gathered by the sequence of events and time history recorders, and for the presentation of this information for oost-trip review and analysis. Based on our review, we find that this information will be presented in a readable and meaningful format, and that the storage, retrieval and presentation conform to the guidelines of Section II C.

l D. The licensee's submittal of December 6,1985 indicates that the data and information used during post-trip reviews will he retained in an accessi-ble manner for the life of the plant. Based on this information, we find that the licensee's program for data retention conforms to the guidelines of Section II D, and is teceptable.

Based on our review of the licensee's submittals, we conclude that the appli-cant's post-trip review data and information capabilities for Wolf Creek Generating Station are acceptable, i

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s TABLE 1 PWR PARAMETER LIST SOE Time History Recorder Recorder Parameter / Signal (1) x Reactor Trip (1) x Safety Injection x Containment Isolation (1) x Turbine Trip x Control Rod Position (1) x x Neutron Flux, Power

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x x Containment Pressure (2) Containment Radiation x Containment Sump Level (1) x x Primary System Pressure (1)x x Primary System Temperature (1) x Pressurizer Level (1)x Reactor Coolant Pump Status

, (1)x x Primary System Flow (3) Safety Inj.; Flow. Pump / Valve Status x MSIV Position x x Steam Generator Pressure (1) x x Steam Generator Level (1) x x Feedwater Flow (1) x x Steam Flow l

SOE Time History Recorder . Recorder Parameter /Sienal (3) Auxiliary Feedwater System: Flow, Pump / Valve Status x

AC and DC System Status (Bus Voltage) x Diesel Generator Status (Start /Stop,

. On/Off) x PORV Position (1) Trip parameters (2) Parameter may be monitored by either an SOE or time history recorder.

(3) Acceptable recorder options 3re; (a) system flow recorded on an SOE recorder, (b) system flow recorded on a time history recorder, or (c) equipment status recorded on an SOE recorder.

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