United States Nuclear Regulatory Commission - Protecting People and the Environment

Mark II Generic Acceptance Criteria for Lead Plants (Generic Letter 78-41)

                                                              GL 78-41
                                UNITED STATES 
                        NUCLEAR REGULATORY COMMISSION 
                           WASHINGTON, D. C. 20555 

                                       Nov 24 1978
Docket No 50-397

Mr. Neil O. Strand
Washington Public Power Supply System
300 George Washington Way
P O Box 968
Richland, WA 99352



Substantial progress made at our meeting of October 19, 1978, with the Mark II
owners toward resolution of the issues related to pool dynamics for the lead
Mark II plants and allocation of staff technical resourses for review of the
generic Mark II Intermediate Program.  The purpose of this letter is to
summarize the meeting results and to state our intent on future efforts
leading to the completion of staff review of these matters.

The most significant developments relate to the method of combining loads and
acceptability of the pool dynamics load criteria as discussed below:

    - The staff believes that further extension of the approval for SRSS
methods to include combining SRV and OBE loads appears possible and certainly
worth the investment of staff and applicant resources to review and develop a
technically justifiable basis for licensing.  We anticipate completion of our
review of this matter before the end of the year, at which time we will
specify conditions for the use of SRSS in the Mark II program.

    - The Mark II owners agreed to adopt the NRC lead plant pool dynamic load
acceptable criteria with a limited number of execptions.  This agreement, in
several cases, was based on favorable consideration of SRSS methods by the
staff.  The exceptions and the program to resolve the exceptions on a generic
basis are described in Enclosure 1.  Resolution of these exceptions to the NRC
criteria is to be accomplished before the end of 1978.



                                    - 2 -

    - The Mark II owners identified the Intermediate Program taks where a
priority review by the staff is needed.  The staff agreed to schedule a
November meeting to discuss staff concerns related to those tasks where
sufficient information has been submitted to warrant a meeting (see enclosure

While this course of action will help to maintain the near term licensing
schedules for the lead plants, resolution of those exceptions taken by the
Mark II owners to the staff's resources.  As a result, we anticipate some
delay in our overall review of the Intermediate Program Tasks through the end
of 1978.

In recent weeks we have received several requests for plant-unique review of
tasks already included in the Mark II owner's Intermediate Program.  We will
not give as high priority to such meetings as we do to gneric program
meetings.  Recognizing the limitations on staff resources, we reiterate the
need for the Mark II owners to utilize the generic Intermediate Program to the
maximum extent possible.  The generic approach to resolution of the pool
dynamics issues provides the greatest potential for completing the licensing
activities in a timely manner for the plants utilizing Mark II containments.


                                     Roger S. Boyd, Director
                                     Division of Project Management
                                     Office of Nuclear Reactor Regulation

1. Exceptions to the NRC Mark II Pool Dynamic Load Acceptance Criteria
2. Priority Intermediate Program Tasks

cc: See next page


                    Exceptions to NRC Mark II Pool Dynamic
                           Load Acceptance Criteria

1.    Pool Swell Elevation (I.B.1.b)*

      The staff will identify before October 30, 1978 additional information
to be provided by the Mark II owners to support their new methodology
descrived in response to Questions 020.68.  The Mark II owners will provide a
schedule for responding to the NRC's information request.

2.    Small Structure Impact Loads (I.B.3.a)

      The Mark II owners will notify the staff of a time when they will be
ready to discuss and justify their revised methodology.

3.    Asymmetric Pool Swell Loads (I.B.5)

      The Mark II owners will send letter report to the staff including the
description and justification of a more realistic methodology for this load
than the bounding methodology described in the NRC acceptance criteria.

4.    SRV Bubble Phasing (II.B.b)

      The owners of the lead Mark II plants will propose a time when they will
be ready to discuss and justify a generic methodology for establishing bubble
phasing for the "T" quencher discharge device.

*Load designation based on Load Summary Table and Acceptance Criteria in
letter dated Sept. 14, 1978 form R. S. Boyd to lead Mark II plants.


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5.    SRV Bubble Frequency (II.B.c)

      The owners of the lead Mark II plants will propose a time when they will
be ready to discuss and justify a new methodology for defining bubble

6.    LOCA/SRV Submerged Drag Loads (III)

      The staff will notify the Mark II owners of an acceptable meeting time
with our consultants to discuss the Mark II owners revised methodology. 
Emphasis will be placed on items III.A.1 and III.A.2 related to the LOCA jet
drag load and the "T" quencher zone of influence.

7.    Submerged Boundary Load During Vent Clearing (I.A.)

      The Mark II owners will send a letter report to the NRC clarifying the
application of this load to the containment walls.  Reference will be made to
observed loads on the walls of the 4T facility.


Enclosure 2

                     Priority Intermediate Program Tasks

     *1.   Dynamic Single and Multi-Vent Lateral Loads

    **2.   Submerged Structure Ring Vortex Model

    **3.   "T" Quencher Submerged Structure Loads

    **4.   "T" Quencher Air Clearing Loads

     *5.   Refined Chugging Loads

    **6.   "T" and Four-Arm Quencher Temperature Limit

    **7.   New Four-Arm Quencher Load Methodology

     *The staff is scheduling a meeting for November 1978 to discuss concerns
associated with our review of these items.

    **The staff has not received sufficient documentation relating to these
tasks to initiate a review.

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