ML20090L775

Discusses Mark I Containment Evaluation - Long Term Program. Long Term Program Developed to Address Pool Dynamic Loads Associated W/Loca & Relief Valve Blowdown Events

ML20090L775
Person / Time
Site:	Monticello
Issue date:	10/07/1975
From:	Mayer L NORTHERN STATES POWER CO.
To:	Ziemann D Office of Nuclear Reactor Regulation
References
10734, NUDOCS 9102120638
Download: ML20090L775 (7)

Text

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NORTHERH STATES POWER COMPANY MIN N E A POLIO. MIN N E ROTA 8840%

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October 7, 1975

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Mr. D. L. Ziemann, Chief (p.Y g

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Dear Mr. Ziemann:

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MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Mark I containment Evaluation - Long Term Program In our May 8 6 30, 1975 letters to you, we explained that a re-evaluation of the Mark I containment for the Monticello Nuclear Generating Plant was being under-taken to demonstrate that the integrity of the existing design would be maintain-ed in the unlikely event that a DBA LOCA occurred.

This re-evaluation was started in response to requests for information from the NRC in letters dated Pebruary 14, 1975 and April 17, 1975. As explained in our May letters, the prograni for this work consisted of both short term and long tenn phases, with the short term eval-uation similar to that performed by GE and discussed with the Staf f in a meeting in Bethesda on April 10, 1975.

The status of this Short Term Program was re-ported in a letter from GE (I.F. Stuart) to A. Giambusso dated July 31, 1975.

The proposed long-term, in depth evaluation is described in this letter.

"he Long f er:u Program has 'veea developed i.o address pool dynamic loads associated with LOCA and relief valve blowdown events.

It consists of a combination of tests, analyses, and the development of acceptance criteria by which the design basis can be assessed. A parallel effort of development of potential modifications vill be included se that they will be ready if required. The objective of the Long Term Program is to verify that the containment is capable of meeting ag-eed-upon criteria and that it vill function as intended for a forty-year life. This program is being undertaken as a joint effort by the ad hoc BWR Mark 1 Containment Owners Group.

It will be conducted on a generic basis to the greatest extent possible to minimize the time to achieve an acceptable overall uniform solution.

The activities of the Long Term Program include the evaluation of LOCA dynamic test data already obtained by GE and their licensee, together with a series of in-plant and out-of-plant tests supported by analytical programs to identify the phenomenological and structural characteristics of the Mark I containment. We recognize that the program duration is longer than originally discussed with yeu, This is a direct result of the increased definition of the long term program now available and the extended scope cf the short term program as documented in ont 9102120638 751007 PDR ADOCK 05000263 1 Ii f 3 y, P

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NORTHE N CTATED POWER COMP 4Y D. L.'Ziemann 2

submittals on that subject. No other program duration changea are known or are anticipated.

We will as a group continue to evaluate our progress in order to take advantage of any schedule 0mprovements which can be made. Specific activities are listed below with a brief summaty of their objectives, expected completion schedule, and deicription of their content, yLIEF VALVE DISCHARGE RELATED ACTIVITIES 1.

In-Plant Test of S/R Valve Discharge for Torus Pressure and Strain Measure-ments, Discharge Pipe Pressure and Water Level Measurements, and Consecutive Valve Actuation Measurements.

Sch edule :

4th Quarter 1975 Objective:

To establish a generic basis for and to refine the phenomenological model used to predict relief valve blowdown loads.

==

Description:==

Conduct a series of single, multiple, and varying consequ-I tive actuation tests in one plant equipped with extensive torus strain and pressure instrumentation, S/R valve dis-charge line water level anc pr essure instrumentation.

2.

Select Plants for Torus Stress Test during Safety / Relief Valve Discharge.

Schedule:

4th Quarter 1975 Objective:

Define the plants appropriate for relief valve strain gage testing.

j

==

Description:==

Establiah plant selection criteria.

Evaluate preltminary test results and ensure that an adequate number of plants are being tested to include applicability to all plants.

3.

Strain Gauge Testing in Representative Plants Schedule:

Start 3rd Quarter 1976 - Complete 3rd Quarter 1976 Objective:

Obtain di;ect torus shell strain meas : ements associated with relief valve actuations to demonstrate structural adequacy.

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Description:==

Perform tests at several representative plans to adequately cover all Mark I designs.

Install strain gauge measurement instrumentation on the torus exterior surface.

Perform single and multiple valve tests and establish fatigue life adequacy for testing plants and plants of common type utilizing these data.

4.

Relief Valve Mitigating Fix (Load Reduction) Testing Schedule:

1st Quarter 1976 Provide quantitative evaluation of different RV discharge Objective:

devices in emati scale for scaling potential devices that

NORTH. 4N CTATED POWER COMF NY Mr. D. L. Ziemann 3

may be backfittable to Mark I.

This is a backup mitigating fix being investigated in parallel with in-plant tests so that a device would be available if k should be needed

later,

==

Description:==

Design various load mitigation devices on a sub-scale

basis, rabricate and install at the Mcss Landing Test Facility and perform appropriate tests to obtain selative performance.

5.

Relief Valve Consecutive Actuation Transient Analysis Schedule:

3rd Quarter 1976 Objective:

Refine analytical methods for predicting discharge pipe pressure and stre is emplification features associated with consecutive relief valve actuations.

==

Description:==

Develop predictive model and verify with results from test data obtained in Item Number 1 above.

Establish methods for applying to all Mark I containments.

6.

Relief Valve Steam Discharge Thermal Mixing Schedule:

1st Quarter 1976 Develop

• echniques for predicting thermal mixing -in the Objective:

e suppression pool during relief valve discharge.

De sc rip tion 1 Consolidate all plant end test facility data available on thermal mixing..

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l LOCA RELATED ACTIVITIES

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1.

Mark I Submergence Pool Swell Test in 4T Facility i

Schedule:

1st Quarter 1976 Obtain pool swell data (ie, surf 2ce velocity, breakthrough 1

Objective:

elevation, etc.) with a closed full scale single. vent containment configuration and vent submergence typical of Mark I, downcomer lateral loads, and establish pool swell and jet Lapingement characteristics.

==

Description:==

Modify 4T racility to simulate Mark I downcomer submergence.

Instrument appropriately and perform tests.

2.

Deteunine Vent Lateral Loads Schedule:

3rd Quarter 1976 - final Objective:

Refine mala vent lateral load values to be expected during a LOCA event.

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4 GTATED POWER COMP.

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==

Description:==

Utilizing data obtained in Item 1 above and data available from GE licensee test programs, to establish load values for all subsequent analyses.

i 3.

Establish LOCA Load Definition Basis t

Schedule:

2nd Quarter 1976 1

l Obiective:

Establish the basis for LOCA loads on all containment structures.

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==

Description:==

Compare all appropriate available LOCA related test facility data.

Establish and verify analytical and exper/ mental baais used to define loads on all other containment structures.

i 4

Define Final LOCA Design Loads Schedule:

3rd Quarter 1976 j

Objective:

Establish final design loads using basis developed in 1

Item 3 above for the analyses to be performed on reference i

plants.

De sc rip tion 1 Before the final structural analysis is performed, define all loads ensuring that adequate attention has been given to all new and applicable test and analytical data.

This will include appropriate seismic loads.

I 5.

Perfona SLress Analysis of Torus, Torus Internals, and Supports and Develop Structural Modifications if Needed.

Schedule:

4th Quarter 1976 and 1st Quarter 1977 i

Objective:

Complete the analysis required ta demonstre te torus structure

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integrity during LOCA.

Develop generic conceptuai design fixes as necessary to make the design conform to the agreed-l l

upon acceptance criteria.

These fixes would be tailored to i

specific plant application during bnplementation.

==

Description:==

Utilizing the LOCA dynamic loads from the tests and analytical programs, perform detailed structural analysis of the repre-i I

sentative riante.

Evaluate results in accordance with estab-lished acceptance criteria and develop genede design modifi-i cations as appropriate.

CmMc. (LOCA AND RELIEF VALVE) ACTIVITIES 4

1.

Establish Criteria for Determining Adequacy of Structural Design Schedule:

2nd Quarter 1976 I

objective:

Develop acceptance criteria to be utilized as the design basis for evaluating the adequacy of the Mark I containments.

==

Description:==

Work with ASME Code Committees and NRC representatives to arrive at a mutually agreeable basic for evaluating structural capability for all Mark I containments. Document for futur e usa

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NORTHL N CTATED POWER COMP 4Y D. L. Zie' nann 5

2.

Conduct Hardware Tests for Potential Structural Fixes if Required Schedule:

4th (uarter 1975 - 1st Quarte; '.>7 '

Objective:

Determins the load capability or s - r.c & critical structural elements as identified in the test and analytical programs.

Desc ription; As critical structura' elements are identified by the various programs, establish a parallel effort to develop accuptable modification.

It may be necessary to mockup and test existing structures or the proposed fixes to determine ultimate cap-i l

ability. Mockups would be tested to destructL on.

3.

Compare to Plant Licensing Basis Schedule:

2nd Quarter 1977 1

Objective:

Establish and justify to the NRC die design adequacies of the torus including fixes, if required, considering all of l

the applied loads.

==

Description:==

Utilizing all load ard strain information produced by the above programs, complete a detailed analysis sf the repre-sentative plants to evaluate the adequacy of all Mark I containments utilizing the agreed-upon acceptance criteria.

l The completion of the Long Term Program is scheduled for mid 1977.

We believe that this program is responsive to NRC requests.

Detailed planning and procure-i ment of lead equipment has already started in order to meet the expected reporting date.

We suggest a meeting with the NRC Staff to be scheduled in October at which time 2

a more detailed discussion of the proposed Long Term Program could be held.

The Short Term Program will have been completed and results documented; thereforg this l

would also be an appropriate time to evaluate the results of that work.

The pro-I posed meeting wculd be conducted with all other members. of the Mark I Containment l

Owners Group and will be arranged by a representative of that group.

l Yours very truly, i

l L. O. Mayer, PE l

Manager, Nuclear Support Services 10M/LLT/ deb i

cc:

J. G. Keppler G. Charnoff MPCA I

Attn: J. W. Ferman

Attachment:

(Notarized'0ath) l

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UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER CQiPANY MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 LETTER DATED OCTOBER 7,

1975, RESPONDING TO NRC RD]UESTS FOR INFORMATION ON CONTAINMENT DESIGS Northern States Power Company, a Minnesota corporation, by this letter dated October 7,1975hereby submits information in response to NRC requescs dated Februa:y 14, 1975, and April 17, 1975, for analyses and programs related to containment design and performance.

Thie request contains no restricted or other defense infonnation.

NORTHERN STATES POWER COMPANY e

CIMMN/

By L d' Wachter l

Vice President, Power Production i

E System Operation l

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On this 7th day of October, 1975, before me a notary public in and for said County, personally appeared L J Wachter, Vice l' resident, Power Productbn and System Operation, and being first duly sworn acknowledged that he is authorized to executa this document in behalf of Northern States Power Company, that he knows the contents thereof and that to the best of his knowledge, information and belief, the statements made in it are true and that it is not interposed for delay.

1 i

pMJ M44 Denise E. Branau Notary Public, Hennepin County, Minnesota My Commission Expires October 10, 1981

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DENISE E. BRANAU h01ARY PUBilC-M1NNE30TA HEMNetM CouMTV Dr coomission Deses Oct.10,1sst

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CONTROL NO: 10734 FILE:

FROM: Northern States Power C

' DATE OF DOC DATE REC'D LTR TWX RPT OTHER Minneapolis, Minn L4J. Wachter 10-7-75 10-9-75 xxx TO:

ORIG CC OTHER SENTBRC PDR v-v Mr. D.L4Ziemann 3-signed 37 SENT LOCAL PDR.m CLASS UNCLASS PROPINFO INPUT NO CYS REC'O DOCKET NO:

xxxxx

'40 50-263 DESCRIPTION:

ENCLOSURES:

Ler te their 5-8-75 and 5-30-75 Itra furn addl info on the Mark I Containment A{Jg ;' ;.

Evulation Long Term Program notarized 9-7-75........

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