ML20151Z070

Discusses B&W Design Requirements Review.List of Individuals Identified as Contacts for Respective Regions or Ofcs & Draft Program Plan Encl for Comment

ML20151Z070
Person / Time
Issue date:	02/03/1986
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20151Z072	List: ML20151Z070 ML20153B982 ML20154N700
References
NUDOCS 8602130534
Download: ML20151Z070 (12)

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UNITED STATES

1. NUCLEAR REGULATORY COMMISSION g E WASHINGTON. D. C. 20555 v

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FEB 0 31986 i

k 4 j MEMORANDUM FOR: Distribution j FROM: Dennis M. Crutchfield, Assistant Director for Technical Support Division of PWR Licensing-B

SUBJECT:

B&W DESIGN REVIEW f

d As identified in Mr. Stello's letter of January 24, 1986 to Mr. Tucker of j the B&WOG, the staff is re-examining the basic design requirements. NRR is responsible for providing overall direction of this effort with support from the Regions and appropriate offices. Enclosure I lists the individuals that have been identified as contacts for their respective Regions or Offices.

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, The schedule in the January 24, 1986 Stello letter calls for the development i' of a detailed program plan by mid-February. Enclosure 2 is a draft program plan provided for your comment.

! A meeting to discuss the comments will be held on Thursday, February 6, 1986,

in my office (P-5008) at 11

00 a.m. Each of the contacts should have their comments provided to me by then and plan to participate in this meeting.

l If you cannot attend, please let me know and you can participate by i conference call. The final program plan will then be put together and l concurrences sought from senior staff management.

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Dennis M. Crute field, ssistant Director for Technical Suppo Division of PWR Licensing-B J

Enclosures:

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- ENCLOSURE 1 FEB 0 31966 DISTRIBUTION Identified Contacts Region I - R. Starostecki Region II - A. Gibson Region III - L. Reyes Region IV - J. Gagliardo Region V - J. Crews IE - E. Jordan RES - F. Gillespie AEOD - J. Heltemes Others V. Stello H. Denton D. Eisenhut NRR Division Directors W. Paulson T. Marsh J. Calvo PWR-B Branch Chiefs J. Stolz C. McCracken R. Weller I

ENCLOSURE 2

1. INTRODUCTION 1

Since the TMI accident, there has been a growing realization of the sensitivity of Babcock and Wilcox (B&W) plants to operational transients. By letter dated January 24, 1986, the Acting EDO informed the Chairman of the Babcock and 4

Wilcox Owners Group (B&WOG) that a number of recent events at B&W designed reactors lead us to conclude that there is a need to re-examine the basic design requirements for B&W reactors. The letter stated that the staff will reassess the overall safety of the B&W plants and determine whether the present set of requirements for B&W plants are appropriate for the long term and lead to a level of safety at BiW riants that is comparable to other i

pressurized water reactors. NRR has been ansipped the responsibility to provide overall direction of this effort ;ith support from the Regions and all appropriate NRC offices. The B&WOG has been asked to take a leadership i role in developing with the NRC the plans for the reassessment effort.

This Task Action Plan outlines the scope, along with the lead and principle evaluation responsibilities to accomplish the reassessment. The target for completing this integrated effort is late Summer 1986.

2. DISCUSSION I To achieve the objectives discussed above, a Task Action Plan has been developed that includes both deterministic and probabilistic assessments, an integrated evaluation to identify potential design, the identification of potential significant improvements to reduce the frequency and severity of anticipated operational transients, and thereby the overall safety of the B&W reactor, and the identification of potential revised licensing criteria.

D. Crutchfield, Assistant Director for Technical Support, Division of PWR Licensing-B, NRR has been designated as the senior staff manager responsible i

! for this program. Figure 1 shows the major tasks and the interfaces between tasks. Table 1 identifies the lead organization responsible for managing and technically directing each task. This table also lists the review organizations which will be supporting the lead organization.

An overview of the tasks shown in Figure 1 is discussed in the following paragraphs.

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3. SCOPE AND CONTENT OF TASKS The study and required information will be based on the following B&W designed plants for which utilities hold operating licenses:

a l Arkansas Nuclear One, Unit 1 (ANO-1) - (Arkansas Power & Light Company)

Crystal River, Unit 3 - (Florida Power Corporation)

Davis-Besse, Unit 1 - (Toledo Edison Company)

Oconee, Units 1, 2 and 3 - (Duke Power Company)

Rancho Seco, Unit 1 - (Sacramento Municipal Utility District)

Three Mile Island, Units 1 and 2 (Metropolitan Edison Company)

The main focus of the study will be the generic assessment of B&W designed reactors and the identification of potential improvements as related to reducing the frequency and severity of anticipated operational occurrences, and thereby improve the overall safety of the B&W reactors. In addition, representative Combustion Engineering (CE) and Westinghouse (W) PWR designs 2

will be selected and compared with the B&W PWR design to assess the relative plant dynamic behavior that would result when confronted with anticipated operational occurrences, as well as their overall safety.

In general, Tasks 3.1 through 3.12 involve a spectrum of assessments, each of which should identify potential system, operations or analysis improvements aimed at increasing the perceived level of safety of the B&W reactors.

Task 3.13 performs an integrated evaluation of all these improvements, without regard to cost / benefit judgements.

3.1 Compile and Assess Previous Staff Reviews of Anticipated Operational Occurrences and the Status of Implementation

! The objectives of this task are to: (1) compile the results of previous reviews of B&W operational occurrences, and (2) summarize the status of the implemen-tation of modifications at each B&W plant resulting from the requirements /

recommendations developed during the previous reviews. Events beginning with the March 20, 1978 Rancho Seco " light bulb" event should be considered.

A detailed list of those events to be reviewed will be developed at the beginning of this task by the lead organization.

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3.2 Review Operating Events This activity will consist of the re-review of past B&W operational occurrences.

The intent of this effort is to look at these events as a set of operational experiences that may indicate common problems, deficiencies, or system weaknesses. The review should include, but should not be limited to, the applicable Licensee Event Reports (LERs), Inspection and Enforcement (IE)

Bulletins, Circulars and Notices and other information involving anticipated operational occurrences and related failures at each of the operating B&W

! plants, and for other PWR vendor plants. This information will be input to

Item 3.3, below.

3.3 Identify Problems, Root Causes, and Sensitive Systems 1

l The results of the review of operating events will be used to identify problem areas, complications in dealing with the event, frequency of occurrence and severity of the events, root causes, and sensitive systems. Also, the review results from these events will be analyzed to verify conformance with the licensing basis for B&W plants.

The general elements of this task are as follows:

Group events in accordance with plant response (e.g., undercooling, overcooling).

Establish screening criteria to select bounding events for detailed review based on the frequency and severity of the events.

Identify problem areas as related to plant-specific and generic implications.

Analyze events for impact on licensing basis as related to hardware, safety analysis, procedures, operator training, conduct of plant operations, and technical specifications.

The approach to be followed for surveying operating reactor events at other vendor plants will be the same as that discussed above for B&W plants, except that the identification of problem areas, root causes, and sensitive i systems will only be correlated to a selected sample of other vendor plants which are representative of plant designs and features. The events from other vendor plants will not be analyzed to determine whether they have an impact on the licensing basis for the selected plants.

3.4 Obtain B&W Plant-Specific Design Information The objectives of this task are to: (1) assemble B&W plant system information (e.g., EFIC, SFRCS, AFW, valve positions on loss of ICS power, etc.), and (2) compile and compare operating B&W plant features. Root causes of plant.

problems should also be used as guidance in defining system information to be

, gathered.

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3.5 Perform System Analyses and Sensitivity Checks Against Current 1 Criteria for A Reference Plant This task will analyze the plant behavior when it is confronted with postulated failures and perturbations. Sensitivity checks will be included in the analysis to establish the plant response boundaries and margins. Current analysis methods and licensing criteria will be used in the analyses. For example, in addition to the assumed initiating event, single failure of active components and the effect of loss-of-offsite power would be considered. Some of the operational occurrences that should be included are as follows:

Loss of normal feedwater Loss of all feedwater Overcooling followed by repressurization

• Undercooling Steam generator overfill

• Reactor vessel overfill

• Turbine trip

• Loss of offsite power PORV or code safety relief valve open

• Steam generator tube failure

• Small break LOCA

• Steam line break spurious signal initiation

• Pressure temperature limit correlations A B&W plant which includes design features, configurations, and capacities that resemble the majority of the B&W plants will be selected as the model for the systems analysis and sensitivity checks.

The same approach for analyzing behavior in B&W plants will be followed during the performance of this task for other vendor plants, except that the plant-specific information data base is limited to selected designs and features.

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3.6 Assess Behavior for Other B&W Plants Plant-specific information vill be used to evaluate the effect of plant-specific system configurations on plant response. This task will extend the analyses performed as described in Section 3.4, above, to all the operating B&W plants.

To the extent possible, those assessments should be based on engineering judgements. Where plant-specific differences are noted to make these judgements not possible, plant-specific analyses may be performed.

3.7 Evaluate Marings and Sensitivities Beyond Regulatory Objectives for Reference Plant This element of the study will determine, based on the identified problems, root causes, and sensitive systems, the margins available beyond the classical regulatory limits, for a representative B&W reactor plant when subjected to a supplemented licensing type review. The study will evaluate standard licensing basis type questions and scenarios, but will address issues beyond the normal licensing limits. The questions and issues considered will be pertinent to

' those effected by the identified problems, root causes and sensitive systems.

Questions regarding multiple failures, consequential equipment malfunctions, operator errors of commission and omission and other failures that are not normally postulated will be considered. The individual evaluations should de te rmine :

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1. The proximity to a regulatory limit,

2. The availability of systems and components to provide mitigation,

3. The information (i.e. , procedures, training, and control room instrumentation) available to the operators, and

4. The time frames within which the operator must act to keep the event under control.

3.8 Assess Behavior for Other B&W Plants Plant-specific information will be used to evaluate the effect of plant-specific features and system configurationc on margins and sensitivities beyond regulatory obj ectives . This task will extend the analyses performed as described in Section 3.6, above, to all B&W operating plants. To the extent possible, those

assessments should be based on engineering judgements. Where plant-specific differences are noted to make these judgements not possible, plant-specific analyses may be performed.

3.9 Review Existing Plant Probabilistic Risk Assessment The objective of this task is to assemble and review existing PRA's that have been performed for B&W plants and other PWR facilities An assessment of the input data should be performed to verify that it is consistent with actual B&W data.

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3.10 Assess B&W PRA's The objectives of this task are to: (1) assess the probability of core melt at B&W plants considering observed operating events, and (2) compare core melt probability among the B&W plants. B&W plant-specific probabilities should be used in the evaluations. Existing plant PRA's (e.g., Midland, Oconee) should be used as tools in developing the task objectives.

3.11 Compare B&W and Other PWR PRA's The objective of this task is to compare the core melt probability at B&W plants with other BWRs using the results of the PRAs.

3.12 Identification of Additional Safety Concerns The main thrust of this element of the study effort is to address concerns that do not readily fall into a particular regulatory area. This element is aimed at describing operational, human factors, system or other concerns that arise in the course of the review of the operational events. For example, in the course of the review of events at B&W reactors, it is apparent that for a given relatively benign loss of feedwater transient, a numb (r of safety systems are challenged. A review of a similar initiating event on a CE or W plant reveals a lesser challenge to safety systems.

Although there are no regulatory limits that restrict reliance on safety systems to particular scenarios, the higher rate of challenge of the B&W

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safety systems has become a concern in the engineering judgment of a number of analysts.

i 3.13 Integrated Assessment to Identify Plant Alternative Improvements This phase of the effort involves a unified assessment of all the recommen-dations, conclusions and suggestions coming from the above described tasks.

Since this could obviously involve a great deal of quantitative and qualitative information, the team should attempt to first organize the various items into

sets or groups. Then, once into groups, the various items should be given a j relative priority based on their perceived safety importance. Some possible

! groups are:

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1. Items that will result in the plant meeting current regulatory requirements.

3 2. Items that are not necessarily needed for regulatory conformance, but are needed for reducing the plant's susceptibility or severe i response to transients, and

! 3. Items that improve the operator's ability to manage transients.

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, This phase of the overall effort should not consider the relative costs / benefits i

of the various recommendations. The items should be considered only in accordance with their perceived safety importance.

3.14 Safety Considerations and Potential Revised Licensing Criteria Based on the results of the integrated evaluation of Item 3.13, above, potential i

plant improvements and revised licensing criteria important to safety will be identified. Any significant potential plant improvements or modifications to licensing bases will be subjected to review in accordance with the requirements of the backfit procedure.

! 3.15 Reduced Transient Sensitivity During the integrated evaluation, poten tial improvements to reduce transient sensitivity may be identified and will be offered for voluntary implementation.

4.0 REPORTS It is expected that the results of selected major tasks will be documented in NUREG reports.

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TABLE 1 i

i TASK ASSIGNMENT RESPONSIBILITY LEAD SUPPORT REVIEW

, TASK DESCRIPTION RESPONSIBILITY RESPONSIBILITY Compile and assess previous staff PWR PD#6 Regions, IE, ORNL l reviews of A00's and status of I implementation.

4 i j Review operating events. FOB /PWR-B PEICSB & RSB/PWR-B,  !

i ORAS, AEOD, IE, ORNL i

l Identify problems, root causes, F0B/PWR-B PEICSB, RSB/PWR-B l and sensitive systems. ORAS, AEOD, IE, ORNL 1

! Perform system analyses and RSB/PWR-B PEICSB & F0B/PWR-B, sensitivity checks against DHFT, PSB/PWR-A, current criteria for a reference F0B/PWR-A plant.

f l Assess behavior for other B&W RSB/PWR-B PEICSB & F0B/PWR-B, i plants. DHFT, PSB/PWR-A, F0B/PWR-A j Evaluate margins and sensitivities RSB/PWR-B PEICSB & FOB /PWR-B, beyond regulatory objectives for DHFT, PSB/PWR-A, a reference plant. F0B/PWR-A Assess behavior of B&W plants. PWR/PD#6 PEICSB & FOB /PWR-B, DHFT, PSB/PWR-A, i

FOB /PWR-A 1

Obtain B&W plant-specific design PWR/PD#6 Regions, F0B/PWR-B l information.

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j Review existing plant probabilistic FOB /PWR-B RRAB/DSRO, RES

, risk assessments.

Assess B&W PRA's. F0B/PWR-B RRAB/DSRO, RES Compare B&W and other PWR PRA's. F0B/PWR-B RRAB/DSRO, RES j

i Identification of additional RSB/PWR-B PEICSB & F0B/PWR-B, i

safety concerns. EIB/PWR-A, ORAS, i DHFT-3 Integrated assessment to identify TBD TBD potential alternatives.

{ Safety considerations and potential TBD TBD i

revised licensing criteria.

1i Reduced transient sensitivity. TBD TBD i r i

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SCHEDULE OF REVIEW Detailed Plan Task Item No. Description Completed Completed 3.1 Previous staff review compilation and implementation status.

3.2 Review operating events.

3.3 Identify problems, root causes, and sensitive systems.

3.4 Obtain B&W plant-specific design info rmation.

3.5 System analyses and sensitivity checks for reference plant.

3.6 Assess behavior of other B&W plants.

3.7 Evaluate margins and sensitivities beyond regulatory objectives for reference plant.

3.8 Assess behavior of other B&W plants.

3.9 Review existing plant PRA's.

3.10 Assess B&W plant PRA's.

3.11 Compare B&W to other PWR PRA's.

3.12 Identification of additional safety Concerns.

3.13 Integrated assessment to identify potential alternative improvements.

3.14 Safety considerations and potential revised licensing criteria.

3.15 Reduced transient sensitivity.

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