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NAC FORM 100 13-01)

US. NUCLEAR REGULA, AV COMMITTION] LIN NUMITA
PROJECT AND BUDGET PROPOSAL FOR NRC WORK

A-3852

DATE

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Review of the Emergency Planning Sensitivity

Project Title: Study for Seabrook

1. OBJECTIVE OF PROPOSED WORK

a. Background

PROJECT DESCRIPTION

P. 3

On July 21, 1986 Public Service of New Hampshire (PSNE) submitted a sensitivity study on the emergency planning zone (EPZ). The study provides a comparison of dose versus distance curves for the Seabrook plant and site with similar generic curves from NUREG-0396 which were used in developing the XPZ regulation in 10 CFR 50.47. The study concludes that a 1-mile evacuation radius at Seabrook provides for a sinilar or greater degree of public protection than was shown by MUREG-0396 for a 10mile evacuation radius around the plants considered by WASH-1400.

The study is largely based on the Seabrook Probabilistic Safety Assessment that PSNH submitted about 3 years ago. The source terms used in the Emergency Planning Sensitivity study were drawn from the source teras used in the WASH-1400 calculations, with some modifications under specific scenarios. Also, some of the probabilistic models have been changed from the Safety Assessment. Thus, the report is intended to examine differences made by the Seabrook design and site, plus the improvements in accident sequence modeling capabilities, without credit for source term reductions that may result from recent studies. The ZPZ study attributes reductions in their offsite dose predictions to the higher strength of the Seabrook containment, a more refined failure modes analysis for the containment, and a more realistic treatsent of the initiation and progression of interfacing systems LOCA sequences. Along with the Emergency Planning Sensitivity Study, PSNH has also submitted a report titled "Seabrook Station Risk Management and Emergency Planning Study," which pro-. vides results of Seabrook specific calculations with new source terms based upon the recent IDCOR work.

The applicant has requested that the technical merits of the EPZ study be reviewed with respect to its adequacy to support a change to the emergency response process. The exact nature of the change has not yet been specified. PSNE has further requested that the review be completed on an expedited basis.

The conclusions of the EPZ Sensitivity Study are based upon comparison of the results of the study to three acceptance criteria that were drawn from NRC documents, One of the criteria is a comparison of the individual risk of early fatality in the population within 1-mile of the plant, assuming no immediate protective action, to the NRC proposed safety goal. A second criterion is the comparison of early fatalities at the Seabrook site, assuming a 1-mile evacuation, to the early fatalities results of WASH-1400, which assumed a 25 mile evacuation. The third criterion is the comparison of the risks of exposure to 1, 5, 50, and 200 rem whole body doses at various distances from the Seabrook site to the corresponding NUREG-0396 results at 10 miles, assuming no immediate protective actions.

To properly review the XPZ Sensitivity Study, it will be necessary to identify the baseline against which comparisons are made, to identify the appropriate criteria for making the comparisons, and to review the basic assumptions and the more significant aspects of the probabilistic calculations.

(See Continuation Sheet)

Review of the Emergency Planning Sensitivity

Project Title: Study for Seabrook

b. Objective

The objective of this effort is to assist the NRC in evaluating the technical validity of the applicant's conclusions regarding the Emergency Planning Sensitivity study for Seabrook.

2. SUMMARY OF PRIOR EFFORTS

A review of the Containment Failure Modes and Radiological Source Terms presented in the Seabrook Station Probabilistic Safety Assessment was performed by BNL under FIN A-3778. However, this review did not evaluate in detail the containment performance under severe accident conditions. Nevertheless, the experience gained by BNL staff under FIN A-3778 will provide useful background for the current review of the Emergency Planning Sensitivity Study for Beabrook.

3. WORK TO BE PERFORMED AND EXPECTED RESULTS

Work Requirements

Task 1: System Evaluation

3KL will review those portions of the Seabrook Emergency Planning Sensitivity Study related to system failure to determine the appropriateness of the calculated accident sequence probabilities. In particular, the probability for interfacing system LOCA will be carefully assessed to determine the potential for containment bypass. BNL will also review the probability of equipment malfunctions, personnel errors, and design errors resulting in containment bypass at the time of a severe accident. Estimated Level of Effort: (FY 86) 2 Professional Staff Months (pam) (TY 87) 1 pen

Estimated Completion Date: October 31, 1986

Task 2: Containment Event Tree Review

BNL will review the conditional probabilities of early containment failure given in the Seabrook submittals. In particular, the vulnerability of the Seabrook containment to uncertainties in containment loads will be carefully assessed. This task will be highly coupled to Task 3, which will assess the performance of the Seabrook containment under severe accident conditions.

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The purpose of this task is to evaluate the technical validity of the applicant's conclusions regarding the behavior of the Seabrook containment under severe accident conditions.

(See Continuation Sheet)

Review of the Emergency Planning Sensitivity

Project Title: Study for Seabrook

3. WORK TO BE PERFORMED AND EXPECTED RESULTS (Cont.)

.. Work Requirements (Cont.)

Task 3: Evaluation of Containment Behavior (Cont.)

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BNL will review and evaluate the relevant containment structural analyses performed by the applicant and its consultants. In addition, a plant site tour and engineering audit at the applicant's (or consultant's) office will be conducted to better understand the containment analyses and design and to identify any unique design features and/or analytical assumptions that merit further investigation.

Based on the above review, BNL will develop an axisymmetric finite element model and perform analyses utilizing BNL's MFAP computer code to confirm the applicant's prediction of the overall capacity of the containment. Special attention will be given to the post-cracking behavior of the concrete which controls the shear failure mode of the containment. To expedite the performance of this task, BNL will utilise, to the maximum extent practical, the input parameters obtained from the applicant's analytical models. In addition, simplified hand calculations will be performed to assess the applicant's conclusions regarding the behavior of selected containment penetration assemblies. Finally, BNL will perform a qualitative assessment of the applicant's seismic fragility analysis of the containment structures, and components. BNL will also support meetings with upper NRC management and the ACRS to describe the interim status of this review, as well as the final results.

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The appropriateness of the new source terms based on RSS methodology used in the Seabrook submittal will be reviewed.

Botimated Level of Effort: (FY 86) 1 pom

Estimated Completion Date: September 30, 1986...

Task 5: Site Consequence Modeling

The site consequence modeling will be reviewed to determine the appropriateness of the consequence calculations presented in the Seabrook submittal. In addition, any consequence calculations found necessary as a result of the work to be performed under Tasks 1-4 will be performed.

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