ML20128K375

Safety Evaluation Re Generic Ltr 83-28,Item 1.1, Post-Trip Review Program Description & Procedure. Post-trip Review Program & Procedures Acceptable,Based on Review of 831105 & s

ML20128K375
Person / Time
Site:	Millstone
Issue date:	07/10/1985
From:	Office of Nuclear Reactor Regulation
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Shared Package
ML20128K368	List: ML20128K365 ML20128K375
References
GL-83-28, NUDOCS 8507240117
Download: ML20128K375 (4)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.

MILLSTONE NUCLEAR POWER STATION, UNIT NO. 2 DOCKET NO. 50-336 GENERIC LETTER 83-28, ITEM 1.1 - POST-TRIP REVIEW (PROGRAM DESCRIPTION AND PROCEDURE)

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 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 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 February 28, 1983, the NRC Executive Director for Operations (ED0), 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 ATWS Events at the Salem Nuclear Power Plant." As a result of this investigation, the Commission (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 Infonnation Capability."

This safety evaluation (SE) addresses Action Item 1.1 only.

II. REVIEW GUIDELINES The following review guidelines were developed after initial evaluation of various utility responses to Item 1.1 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 reviewed the licensee's response to Item 1.1 against these guidelines:

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. A. The licensee or applicant should have systematic safety assessment procedures established that will ensure that the following restart l

criteria are met before restart is authorized.

The post-trip review team has determined the root cause and sequence '

of events resulting in the plant trip.

Near term corrective actions have been taken to remedy the cause of the trip.

The post-trip review team has performed an analysis and determined that the major safety systems responded to the event within specified limits of the primary system parameters.

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• The post-trip review has not resulted in the discovery of a potential safety concern (e.g., the root cause of the event occurs with a frequency significantly larger thaa expected).

l If any of the above restart criteria are not met, then an independent assessment of the event is performed by the Plant

Operations Review Comittee (PORC), or another designated group with similar authority cnd experience.

B. The responsibilities and authorities of the personnel who will perfonn the review and analysis should be well defined.

l' The post-trip review team leader should be a member of plant management at the shift supervisor level or above and should hold l or should have held an SRO license on the plant. The team leader '

should be charged with.overall responsibility for directing the post-trip review, including data gathering and data assessment and he/she should have the necessary authority to obtain all personnel and data needed for the post-trip review.

i A second person on the review team should be an STA or should hold a relevant engineering degree with ,pecial transient analysis training.

, The team leader and the STA (Engineer) should be responsible to concur i on a decision / recommendation to restart the plant. A nonconcurrence I

from either of these persons should be sufficient to prevent restart until the trip has been reviewed by the PORC or equivalent organization.

C. The licensee or applicant should indicate that the plant response to the

' trip event will be evaluated and a determination made as to whether the plant response was within acceptable limits. The evaluation should include:  :

A verification of the proper operation of plant systems and l equipment by comparison of the pertinent data obtained during the I post-trip review to the applicable data provided in the FSAR.

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An analysis of the sequence of events to verify the proper functioning of safety related and other important equipment. Where possible, canparisons with previous similar events should be made.

D. The licensee or applicant should have procedures to ensure that all physical evidence recessary for an independent assessment is preserved.

E. Each licensee or applicant should provide in its submittal, copies of the plant procedures which contain the information required in Items A through D. As a minimum, these should include the following:

l The criteria for determining the acceptability of restart

--- The qualifications, responsibilities and authorities of key l-personnel involved in the post-trip review process The methods and criteria for determining whether the plant variables and systen responses were within the limits as described in the FSAR

The criteria for determining the need for an independent review.

III. EVALUATION AND CONCLUSION By letters dated November 5, 1983, and May 28, 1985, the licensee of Millstone Nuclear Power Station, Unit 2, provided information regarding its Post-Trip Review Program and Procedures. We have evaluated the licensee's program and procedures against the review guidelines developed as described in Section II. - A brief description of the licensee's response and the staff's evaluation of the response against each of the review guidelines is provided below:

A. The licensee has established criteria for' determining the acceptability

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of restart. Based on our review, we find that the licensee's criteria conform with the guidelines as described in the above Section II.A and, therefore, are acceptable B. The qualifications, responsibilities and authorities of the personnel who will perform the review and analysis have been clearly described.

We have reviewed the licensee's chain of command for responsibility for post-trip review and evaluation, and find it acceptable.

C. The licensee has addressed the methods and criteria for comparing the event information with known or expected plant behavior. Based on our review, we find them to be acceptable.

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l D. The licensee has indicated that independent assessment conducted by the PORC is required for all events. In addition, the licensee has established procedures to ensure that all physical evidence necessary for an independent assessment is preserved. We find that these actions taken by the licensee confom with the guidelines as described in the above Section II.A and D.

E. The licensee has provided for our review a systematic safety assessment program to assess unscheduled reactor trips. Based on our review, we find that this program is acceptable.

Based on our review, we conclude that the licensee's Post-Trip Review Program and Procedures for Millstone Nuclear Power Station, Unit 2, are acceptable.

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Date: July 10, 1985 Principal Contributor:

D. Shum, DHFS

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