ML20138M192

Safety Evaluation Re Review of Util Response to Generic Ltr 83-28.Post-trip Review Data & Info Capabilities Re Item 1.2 May Be Inadequate for Diagnosing Causes of Unscheduled Reactor Shutdowns & for Evaluating safety-related Equipment

ML20138M192
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	10/03/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20138M182	List: ML20138M180 ML20138M192
References
GL-83-28, NUDOCS 8510310573
Download: ML20138M192 (11)

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pena jo, UNITED STATES y .

y j NUCLEAR REGULATORY COMMISSION E

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f EhCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO OPERATION OF ZION NUCLEAR POWER STATION UNIT 1 AND 2 COMMONWEALTH EDIS0N COMPANY DOCKET NOS: 50-295 AND 50-304 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 plant start-up and the reactor was tripped manually by the operator about 30 seconds after initiation of the automatic trip signal. Failure of the circuit breakers has been detemined to be related to sticking of the

, under voltage trip attachment. , On February 22, 1983, an automatic trip occurred during start-up of SNPP Unit 1 as a result of steam generator low-low level. In this case, the reactor was tripped manually by the -

operator almost coin ~cidentally with the automatic trip. On February 28,

, 1983,'the NRC EEecutive Director for Operations, directed the staff to Investigate and report on the generic implications of these occurrences at the Salem Nuclear Power Plant. The results of this staff investigation are reported in NUREG-1000, " Generic Implications of the ATWS Events.at the Salem Nuclear Power Plant." As a results of thi:: investigstion, the Comission requested (byGenericLetter83-28datedJuly.8,1983)alllicenseesof l cperatin'g reactors, applicants for an operating license, and holders of

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construction pemits to respond to certain generic concerns. Th'ese concerns are categorized into the following four areas: (1) Post-TripReview, .

8510310573 851003 PDR ADOCK 05000295 P PDR

l (2)EquipmentClassificatienandVendorInterface,(3) Post-Maihitenance Testing, and (4) Reactor Trip System Reliability Improvements.

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l The first action item, Post-Trfp Review, consists of Action Item 1.1, "Progrsm Description and Procedure" and Action Item 1.2, " Data and Infonnation Capability." This evaluation addresses Action Item 1.2 only.

II. REVIEWGU5DELINES 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. Therefore, these review '

guidelines effectively represent a " good practices" approach to post-trip review. We have reviewed the Itcensee's response to Item 1.2 against these

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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 infomation to be used in the post-trip review. Each plant variable which is necessary to detennine 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. Perfomance characteristics guidelines for SOE and time history recorders are as follows: .

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Each sequence of events recorder should be capable of detecting 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 it can be detenqined if the time response is githin acceptable limits based on FSAR Chapter 15 Accident Analyses. The reccernended 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

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transient and accident scenarios presented in Chapter 15 of the '

FSAR.

Each analog time history data recorder should have a sample -

interval srall 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 analysis of Chapter 15 of the FSAR. The recomended 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

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transient and accident sequences presented in Chapter 15 of the FSAR. To support the post-trip analysis of thEcause of the trip and the proper functioning of safety-related equipment, each analog time history data recorder should be capable of updating and retaining infonnation from approximately five minutes prior to the reactor trip until at least ten minutes after the trip.

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• All equipment used to record sequence of events and time history

. infonnation should be powered from a reliable and non-interruptible power source. The power source used need not be Class IE.

B. The sequence of events and time history recording equipment should

-~ monitor sufficient digital and analog. parameters, respectively, to ,

assure that the course of the reactor trip and post-trip events can be*

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' reconstructed. 'The parameters monitored should provide sufficient

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> 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 associated with reactor trips, safety injections and other safety-related systems as well as output parameters sufficient to record the proper functions of these systems should be recorded for use in the post-trip review.-The minimum parameters necessary to determine if the plant remained wit'hin its l

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6-safety limits are presented in Table 1. The parameter lis't was based on staff engineering judgment following a complete evaluation of utility submittals. If the SOE recorders and time history recorders do not monitor all of the parameters suggested in this table the licensee should justify the adequacy of existing monitored parameters to establish that the plant remained within the design conditions analyzed

__ _ in Chapter 15 of the FSAR.

C. .,The information gathered by the sequence of events and time history recorders should be stored in a manner that will allow for dats retrieval and analysis. The data may be retained on hardcopy, (e.g.,

computer printout, strip chart record), or in an accessible memory.

. (e.g.,magneticdiscortape). This information should be presented in

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a readable and meaningful fonnat, tak4ng into consideration good human '

. factors practices such as those outlined in NUREG-0700.

D. Data from all unscheduled shutdowns provides a valuable reference source for 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.

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III. EVALUATION AND CONCLUSION .'

I By letter dated November 5,1983, the Connonwealth Edison Company provided information regarding its post.. trip review program data and infonnation capabilities for Zion Station Units 1 and 2. We have evaluated the licensee's submittal against the review guidelines described in Section II.

Deviations from the Guidelines of Section II were discussed with representatives of the licensee by telephone on August 29, 1985. A brief description o'f the licensee's responses and the staff's evaluation of the response against each of the review guidelines follows:

A. The licensee has described the perforinance 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 submittal, we find that the sequence of events recorder characteristics *

. confonn to the guidelines described in Section II A, and are acceptable. ,

Our review determined that the time history recorder sampling rate is once per minute, which is significantly slower than the recommended .

sampling rate of once per 10 seconds. However, during our telephone

conversation the licensee stated that a new trip log program to record time history data is being developed. Selected analog data will t,e sampled at 10-second intervals and will be recorded to ensure a 5-minute

pre-trip and 10 minute post-trip record. Based on this infonnation, we l

find that the time history recorder characteristics will confonn to the guidelines described in Section II A, and will be acceptable. The

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Itcensee should be requested to provide a documented descr,iption of the trip log program and a schedule for its implementation at Zion Station.

B. The licensee has established and identified the parameters to be monitored and recorded for post-trip review. Based on our review and telephone conversation, we find that the parameters selected by the

-- Itcensee do not confonn to the guidelines described in Section II B.

The licensee does not record all of the sequence of events and time

. history parameters recomended in Table I. No infonnation has been provided to suggest that the existing set of monitored data will be adequate to support a post-trip review for the purpose of detennining if the plant remained within the design envelop for the accident conditions

. analyzed in Chapter 15 of the plant FSAR.

We recomend that the following parameters be recorded by the licensee" on the sequence of events recorder or the time history recorder:

Containment Radiation. This parameter may be recorded either as a

, digital signal on the sequence of events recorder or as an analog l value on the time history recorder. We are unable to detennine that the current strip-chart recording of containment radiation is adequate to serve as a time-history record. , ,

Containment Isolation. We recomend that centainment isolation status be monitored and recorded on the sequence of events recorder.

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Control Rod Position. We recomend that control rod sition be recorded on the sequence of events recorder in order to establish the time of rod insertion in relation to the times of automatic and

{ manual reactor trip signals.

• MSIV Position. We recomend that MSIY position be provided on the

..- -. sequence of events recorder.

PORY Position. We recomend that PORY position be provided on the sequence of events recorder.

C. During our telephone discussion, 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 *

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information for post-trip review and analysis. The licensee stated that

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time, parameter name and any related set point infonnation are provided.

Based on our review of the licensee's submittals and this discussion, we find that this infonnation will be presented in a readable and meaningful format, and that the storage, retrieval and presentation

! conform to the gu'idelines of Section II C.

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! D. Information provided by the licensee during our telephone conversation indicates that the data and information used during post-trip reviews I

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-9 will be retained in an accessible manner for the life of the plant.

Based on this infonnation, we find that the licensee's program for data retention conforms to the guidelines of Section II D, and is acceptable.

Based on our review of the licensee's submit,tals and our telephone conversatfog with the licensee, we conclude that the licensee's post-trip review data and infonnation capabilities for Zion Station Units I and 2 may be inadequate for diagnosing the causes of unscheduled reactor shutdowns and for ascertaining the proper functioning of safety-related equipment. We recomend that the' licensee augment their current list of recorded parameters to include all of those described in Table I. Alternatively, the licensee should supplement their November 5,1983 submittal with additional detail

. justifying the adequacy of those parameters selected for diagnosing an unscheduled reactor shutdown. We also recomend prompt installation of an *

. updated time-history recorder to provide once-per-ten-second parameter samp1.ing capabil,ity.'

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TABLE 1 PWR PARAMETER LIST .

i SOE Time History Recorder Recorder Parameter / Signal l (1) x Reactor Trip (1)x Safety Injection x Containment Isolation

.. (1)x Turbine Trip x -

Control Rod Position (1)x, x NeutronFlux, Power x x Containment Pressure 1

(2) Containment Radiation

x Containment Sump Level

[ (1)x x Primary System Pressure

' (1)x x Prjaary System Temperature ,

(1)x Pressurizer Level -

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(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 Pressure (1)x x Steam Generator Level (1)x x Feedwater Flow (1)x x Steam Flow -

(3) Auxiliary Feedwater System: Flow,

! Pump / Valve Status l

s_ _ . _. . _. _ . _.-_.. . ... _ _... _ _ _.. __. . .

• ew' q Time History D. '

SOE Recorder C  ? a.*

Recorder Parameter / Signal l x ACandDCSystemStatus(BusVoltage) x Diesel Generator Status (Start /Stop, On/Off) x PORY Position (1) Trip parameters (2) Parameter may be monitored by either an SOE or time history recorder.

(3) Acceptable recorder options are; (a) system flow mcorded 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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