ML20133A389

Safety Evaluation Re Review of Generic Ltr 83-28,Item 1.2, Post-Trip Review. Post-trip Review Data & Info Capabilities Adequate

ML20133A389
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/27/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20133A371	List: ML20133A367 ML20133A389
References
GL-83-28, TAC-53591, NUDOCS 8508050458
Download: ML20133A389 (6)

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y*....j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PUBLIC SERVICE COMPANY OF COLORADO l FORT ST. VRAIN UNIT 1 DOCKET FO. 50-267 GENERIC LETTER 83-28. ITEM 1.2 - POST-TRIP REVIEW (DATA AND INFORMATION CAPABILITY)

I. INTRODUCTION On February 25, 1983, both of the scram circuit breakers at Unit 1 of the Salem Nuclear Power Plant failed to open upon an automatic reactor trip This incident occurred during the signal from the reactor protection system.

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 detennined to be related to the sticking of the under voltage trip attachment. Prior to this incident, on February 22, 1983, at Unit 1 of the Salem Nuclear Power Plant, an automatic trip signal was In 9enerated based on steam generator low-low level during plant start-up.

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 at Unit 1 of the Salem Nuclear Power Plant. The results of the staff's inquiry into the generic implications of the Salem unit incidents are reported in NUREG-1000, " Generic Implications of the ATWS Events at the Salem Nuclear Power Plant." As a result of this investigation, the Comission (NRC) 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 Improvements.

The first action item, Post-Trip Review, consists of Action Item 1.1,

" Program Description and Procedure" and Action Item 1.2, " Data and Information Capability." This safety evaluation (SE) 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. The staff has reviewed the licensee's response to Item 1.2 against these guidelines:

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l 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 detemine 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:

• 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 that a detemination can be made as to whether the time response is within acceptable limits based on FSAR Chapter 15 Accident Analyses. The recomended guidelines for the SOE time discrimination is approximately 100 millisecorlds. 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 transient and accident scenarios presented in Chapter 15 of the plant FSAR.

• 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 analysis of Chapter 15 of the plant 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 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 functioning of involved safety related equipment, each analog time history data recorder should be capable of updating and retaining infomation from approximately 5 minutes prior to the trip until at least 10 minutes after the trip.

• All equipment used to record sequence of events and time history infomation should be powered from a reliable and non-interruptible power source. The power source used need not be safety related.

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' 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 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 associated with reactor trips, safety injections and other safety-related systems as well as output parameters sufficient to record the proper functioningThe of these systens should be recorded for use in the post-trip review.

parameters deemed necessary, as a minimum, to perfom 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 licensee'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 parameters is sufficient to establish that the plant remained within the design envelope for the accident conditions analyzed in Chapter 15 of the plant FSAR.

4 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., computer printout, strip chart record), or in an accessible memory (e.g., magnetic disc or tape). This information should be

[ presented in a readable 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 letter dated November 4,1983, Public Service Company of Colorado provided information regarding its post-trip review program data and informationThe sta capabilities for Fort St. Vrain Unit 1. Licensee submittal against the review guidelines described in Section II.

deviations from the Guidelines of ASection II were reviewed brief description with the licensee of the licensee's by telephone on May 21 and 22, 1985.

responses and the staff's evaluation of the response against each of the review guidelines is provided below:

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A. The licensee's submittal described the performance characteristics of the equipsent used to record the sequence of events and time history recorder data needed for post-trip review. Based on the staff's review, the staff finds that the sequence of events and time history recorder characteristics conform to the guidelines described in Section II A, and are acceptable.

B. The licensee has established and identified the parameters to be monitored and recorded for post-trip review. The parameters identified in the submittal of November 4,1983, as being recorded by the sequence of events and time history recorders, did not correspond to the parameters specified in Section II B of this report. The missing parameters were: (1) Reactor Buf1 ding Temperature, (2) RSIV position, (3) Hot Reheat Steam Pressure, (4) Hot Reheat Steam Temperature, and (5) Hot Reheat Steam Activity. By telecon on May 21 and 22,1985 Public Service Company of Colorado verified that these parameters are recorded and meet the criteria of Section II B in this report. Based on the staff's review, the staff finds 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 are, therefore, acceptable.

C. The licensee has 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 post-trip review and analysis. Based on the staff's review, the staff finds 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.

D. The licensee's submittal indicates that the data and information used during post-trip reviews would be retained in an accessible manner for the life of the plant. Based on the staff's review, the staff finds that the licensee's program for data retention conforms to the guidelines of Section II D, and is acceptable.  ;

Based on this review, the staff concludes that the licensee's post-trip review data and information capabilities for Fort St. Vrain Unit I are acceptable.

i Principal Contributor: l R. G. Ramirez, DHFS Date: June 27, 1985 l 1

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.5- l TABLE 1 HTGR POST-TRIP REVIEW PARAMETER LIST SOE Time History .

Recorder Recorder (2) Parameter / Signal x Reactor Trip x Turbine Trip x Control Rod Position x (1) x Neutron Flux, Power x(1) x Reactor Building Temperature x Reactor Building Radiation

- x(1) x Primary System Pressure x Core Region Outlet Temperature x(1) x Circulator Inlet Temperature x (1) Circulator Speed x (1) Circulator Seal Malfunction x(1) Circulator Bearing Water Malfunction x(1) Circulator Drain Malfunction x (1) Circulator Penetration Overpressure

% Primary System Flow x

x(1) x Primary System Moisture x MSIV Position x RSIV Position x(1) x Main Steam Pressure x(1) x Main Steam Temperature x(1) x Hot Reheat Steam Pressure x (1) x Hot Reheat Steam Temperature x(1) Hot Reheat Steam Activity x (1) Steam Generator Penetration Overpressure x Feedwater Flow x Steam Flow l

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x Emergency Auxiliary Feedwater System; Flow, Valve Status l

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6-SOE Time History Recorder (2) Parameter / Signal Recorder AC and DC System Status x

x Diesel Generator Status (1) Trip parameters (2) Parameter may be monitored by either an SOE or time history recorder

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