ML20205C062

Safety Evaluation Accepting Util 831107 Response to Generic Ltr 83-28,Item 2.1, Post-Trip Review. BWR Parameter List Encl

ML20205C062
Person / Time
Site:	Pilgrim
Issue date:	07/31/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20205C034	List: ML20205C029 ML20205C062
References
GL-83-28, NUDOCS 8608120239
Download: ML20205C062 (6)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATIVE TO GENERIC LETTER 83-28, ITEM 1.9 - POST-TRIP REVIEW BOSTON EDISON COMPANY PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293

1. 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 the start-up of the 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 (ED0) directed the staff to investicate and report on the generic implications of these occurrences. The results of the staff's inquiry into~these incidents are reported in NUREG-1000, " Generic Implications of ATWS Events at the Salem Nuclear Power Plant." As a result of this investigation, the Connission 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 ara categorized into four areas (1) Post-Trio Review, (2) Equipment Classifica-ti w and Vendor Interface, (3) Post-Maintenance Testing, and (4) Reactor Trip Sys+>m 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 addresses Action Item 1.2 only.

2. 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.

A. The equipment that provides tne digital sequence of events (S0E) 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 l post-trip review. Each plant variable which is necessary to determine I the cause and progression of the events following a post trip should be j e608120239 e60731 PDR ADOCK 05000293 p PDR

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. 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:

o Each sequence of events recorder should be capable of detecting and recording the sequence of events with a sufficient time discrimina-tion 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 the accident analyses in Chapter 14 of the plant FSAR. The recomended 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 transient and accident scenarios presented in Chapter 14 of the 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 analyses in Chapter 14 of the 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 14. To support the post-trip analysis of the

cause of the trip and the proper functioning of involved safety l related equipment, each analog history data recorder should be I

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

l B. The sequer ,;e 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-trio events can be reconstructed. The parameters monitored should provide sufficient information to determine the root cause of an unscheduled shutdown, the i progression of the reactor trip, and the response of the plant parameters i and protection and safety systems to the unscheduled shutdown.

Specifically, all input parameters associated with reactor trips, safe *y I 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 I

determine if the plant remained within its safety limit design envelope l are presented in Table 1. They were selected on the basis of staff

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, 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 are sufficient to establish that the plant remained within the design' envelope for the accident conditions analyzed in Chapter 14 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 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.

3. EVALUATION By letter dated November 7, 1983, the Boston Edison Company provided informa-tion regarding its post-trip review program data and information capabilities for Pilgrim Station. We have evaluated the licensee's submittal against the review guidelines described in Section 2. Deviations from the guidelines were discussed with representatives of the licensee by telephone on February 12 and 26, 1986. A brief description of the licensee's responses and the staff's

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evaluation of the responses against each of the review guidelines follows:

A. The licensee has described the performance characteristics of the equip-ment 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 and the information provided by the licensee during the telephone conversa-tions, we find that the sequence of events recorder and time history recorder characteristics conform to the guidelines described in Section 2A, and are acceptable.

B. The licensee has established and identified the parameters to be monitored and recorded for post-trip review. The parameters selected by the licensee include all but one of those identified in Table 1. While diesel generator Status is not included as a parameter, there are indicators in the control room that previde this information.

Consequently, we find that the licensee's selection of parameters meets the intent of the guidelines described above in Section 2B and is, therefore, acceptable.

C. The licensee described the means for storage and retrieval of the infonnation gathered by the sequence of events and time history recorders, and fcr the presentation of this information for post-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 above guidelines of Section 2C.

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. 4 D. During the February 26, 1986 telephone conversation, the licensee stated that the data and information used during post-trip reviews are.being retained in an accessible manner for the life of the plant. Based on this information, we find that the licensee's program for data retention conforms to the above guidelines of Section 2D and is acceptable. l

4. CONCLUSION ,

1 Based on our review of the licensee's submittal and the telephone conversations with the licensee, we conclude that the licensee's post-trip review data and information capabilities for Pilgrim Station are acceptable.

Principal Reviewer: Joel J. Kramer Dated:

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TABLE 1 BWR PARAMETER LIST SOE Time History Recorder Recorder Parameter / Signal x Reactor Trip x Safety In,iection x Containment Isolation x Turbine Trip x Control Rod Position x (1) x Neutron Flux, Power x(1) Main Steam Radiation (2) Containment (Dry Well) Radiation x (1) x Drywell Pressure (Containment Pressure)

(2) Suppression Pool Temperature x (1) x Primary System Pressure )

x (1) x Primary System level x MSIV Position x (1) Turbine Stop Valve / Control Valve Position x Turbine Bypass Valve Position x Feedwater Flow x Steam Flow (3) Recirculation; Flow, Pump Status x (1) Scram Discharge Level x (1) Condenser Vacuum 1

, SOE Time History Recorder Recorder Parameter / Signal x AC and DC System Status (Bus Voltaae)

(3)(4) Safety In,iection; Flow, Pump / Valve Status x Diesel Generator Status (On/Off, Start /Stop)

(1) Trip parameters (2) Parameter may be recorded by either an SOE or time history recorder.

(3) Acceptable recorder options are: (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.

(4) Includes recording of parameters for all applicable systems from the following: HPCI, LPCI, LPCS, IC, RCIC.

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