ML20127E778

Safety Evaluation Re Generic Ltr 83-28,Item 1.2 Concerning post-trip Review Data & Info Capability

ML20127E778
Person / Time
Site:	Brunswick
Issue date:	06/10/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20127E769	List: ML20127E766 ML20127E778
References
GL-83-28, NUDOCS 8506240652
Download: ML20127E778 (10)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO GENERIC LETTER 83-28, ITEM 1.2 - POST-TRIP REVIEW DATA AND INFORMATION CAPABILITY CAROLINA POWER & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT UNITS 1 AND 2 DOCKET NOS.: 50-324, 50-325 I. INTRODUCTI0h 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 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 af ter 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 generated based on steam generator low-low level during plant start-up. In this case, the reactor was tripped manually by the operator almost coincidentally with the automatic trip. Following these incidents, on Februa ry 28, 1983, the NRC Executive Director for Operations (EDO), 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 Connission (NRC) requested (by Generic Letter 83-28 dated July 8, 1983) all licensees of operating reactors, applicants for an operating license, and holders of I

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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 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 guidclines in effect represent a " good practices" approach to post-trip review. We have reviewed the licensee's response to Item 1.2 against these guidelines:

A. The equipment that provides the digital sequence of ever.ts (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 ccmputer) for digital parameterst 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:

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 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 15 of the plant FSAR.

l Each analog time histnry 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 recommended guideline for the sample interval is 10 seconds. If the time history eq'uipment does not meet this guideline, the iicensee 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 information from approximately five minutes prior to the trip until at least ten minutes after the trip.

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 safety related.

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 functioning of these

systems shculd be recorded for use in the post-trip review. The parameters deemed necessary, as a minimum, to perform a post-trip review that would detennine 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 are sufficient to establish that the plant remained within the design envelope 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., 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 7,1983, Carolina Power and Light Company provided ~

information regarding its post-trip review program data and information capabilities for Brunswick Steam Electric Plant Units 1 and 2. We have evaluated the licensee's submittal against the review guidelines described in Section II. Licensee deviations from the Guidelines of Section II were

. reviewed with the licensee by telephone on May 21, 24 and 30,1985. A brief description of the licensee's responses and the staff's evaluation of the response against each of the review guidelines is provided below:

A. 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, we find that the sequence of events and time history recorder characteristics conforn 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 subnittal of November 7,1983, 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. These parameters were missing: (1) Certainment Isolation, (2) Turbine Bypass Valve

Position, and (3) AC and DC System Status. By telecon on May 21, 24 and 30, 1985 Carolina Power and Light Company verified that these parameters are recorded and meet the criteria in Section II B of this report.

Infomation on these parameters is stored on the 80P Post Trip Log from two minutes before, to two minutes after, a reactor trip.

Although the DC System Status is not recorded on the SOE, the loss of any DC bus will be annunciated and recorded on the alam printer. This was detemined by telecon May 24, 1985. Based on our review of the November 7,1983 submittal and with the clarifying infomation obtained during our telephone calls, 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 are, therefore, acceptable.

C. The licensee has described the means for storage 7.nd retrieval of the infomation 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 our review, we find that this infomation will be presented in a readable and meaningful fomat, and that the storage, retrieval, and presentation confom to the guidelines of Section 11 C.

D. By telephone call on May 21, 1985, the licensee explained that the data and infomation used during post-trip reviews is retained in an accessible manner for the life of the plant. Based on our I

8-review, 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, we conclude that the licensee's post-trip review data and information capabilities for Brunswick Steam Electric Plant Units 1 and 2 are acceptable.

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TABLE 1 BWR PARAMETER LIST SOE Time History Recorder Recorder Pa rameter/.'. ignal x Reactor Trip x Safety Injection x

Containment Isolation x Turbine Trip

. x Control Rod Position x (i) x Neutron Flux, power x (!) Main Steam Radiation

(?) Containment (Dry Well) Radiation x (.t) 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

r SOE Time History Recorder Recorder Parameter /Sional x

AC and DC Systen Status (Bus Voltage)

(3) (4) Safety Injection; Flow, Pump / Valve Status x Diesel Generator Status (on/0ff, 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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