ML20148L800

Forwards RAI to Complete Review of Licensee Submittal Re Erosion of Cement from Porous Concrete Subfoundations at Plant

ML20148L800
Person / Time
Site:	Millstone
Issue date:	06/16/1997
From:	Andersen J NRC (Affiliation Not Assigned)
To:	Carns N NORTHEAST NUCLEAR ENERGY CO.
References
TAC-M96402, NUDOCS 9706190387
Download: ML20148L800 (6)

Text

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Mr. Neil S. Carns 2

Senior Vice President June 16, 1997 and Chief Nuclear Officer Northeast Nuclear Energy Company c/o Ms. Patricia A. Loftus Director - Regulatory Affairs P.O. Box 128 Waterford, CT 06385

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION REGARDING EROSION OF CEMENT FROM POROUS CONCRFTE SUBFOUNDATIONS (TAC NO. M96402)

Dear Mr. Carns:

I

' By letter dated April 30, 1997, Northeast Nuclear Energy Company (licensee) submitted additional information regarding the erosion of cement from the underlying porous concrete drainage system at Millstone Unit 3. The NRC staff i has reviewed the information and seeks clarification of the information '

provided by the licensee's consultants in their reports.

In order to support further NRC evaluation, the licensee is requested to i provide the NRC with answers to the enclosed questions. Please respond to ,

this request for additional information expeditiously in order for the staff I 5

to complete its review in a timely manner.

Sincerely, 1

Original signed by:

3 James W. Andersen, Project Manager Special Projects Office - Licensing Office of Nuclear Reactor Regulation Docket No. 50-423 l

Enclosure:

As stated I

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+o June 16, 1997 Mr. Neil S. Carns '

l Senior Vice President i and Chief Nuclear Officer l Northeast Nuclear Energy Company c/o Ms. Patricia A. Loftus

Director - Regulatory Affairs l P.O. Box 128 Waterford, CT 06385

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION REGARDING EROSION OF CEMENT FROM POROUS CONCRETE SUBFOUNDATIONS (TAC NO. M96402)

Dear Mr. Carns:

By letter dated April 30, 1997, Northeast Nuclear Energy Comptny (licensee) ,

submitted additional information regarding the erosion of cement from the underlying porous concrete drainage system at Millstone Unit 3. The NRC staff has reviewed the information and seeks clarification of the information provided by the licensee's consultants in their reports.

In order to support further NRC evaluation, the licensee is requested to provide the NRC with answers to the enclosed questions. Please respond to this request for additional information expeditiously in order for the staff 1 to complete its review in a timely manner.

Sincerely, ames W. Andersen, Project Manager ,

, Special Projects Office - Licensing l Office of Nuclear Reactor Regulation Docket No. 50-423

Enclosure:

As stated cc w/ encl: See next page j l

l

c )

1 Northeast Nuclear Energy Company Millstone Nuclear Power Station Unit 3 cc:

\

Lillian M. Cuoco, Esquire Mr. William D. Meinert j Senior Nuclear Counsel Nuclear Engineer {

Northeast Utilities Service Company Massachusetts Municipal Wholesale P. O. Box 270 Electric Company Hartford, CT 06141-0270 '

P. O. Box 426

' Ludlow, MA 01056 Mr. Kevin T. A. McCarthy, Director -

Monitoring and Radiation Division Joseph R. Egan, Esquire 1

Department of Environmental Protection Egan & Associates, P.C.

79 Elm Street i 2300 N Street, NW Hartford, CT 06106-5127 Washington, D.C. 20037 i

Regional Administraice Region I Mr. F. C. Rothen j U.S. Nuclear Regulatot., 'ommission Vice President - Nuclear Work Services )

475 Allendale Road Northeast Nuclear Energy Company i King of Prussia, PA 1940t P. O. Box 128 Waterford, CT 06385

First Selectmen Town of Waterford Ernest C. Hadley, Esquire

' Hall of Records 1040 B Main Street 200 Boston Post Road P. O. Box 549 Waterford, CT 06385 West Wareham, MA 02576

' l Mr. Wayne D. Lanning Mr. John Buckingham i Deputy Director of Inspections Department of Public Utility Control 4

Special Projects Office Electric Unit 475 Allendale Road 10 Liberty Square

King of Prussia, PA 19406-1415 New Britain, CT 06051 Michael H. Brothers Mr. James S. Robinson Vice President - Millstone Unit 3 Manager, Nuclear Investments and Northeast Nuclear Energy Company Administration P. O. Box 128 New England Power Company i

J Waterford, CT 06385 25 Research Drive Westborough, MA 01582 Mr. M. R. Scully, Executive Director Connecticut Municipal Electric Mr. D. M. Goebel Energy Cooperative Vice President - Nuclear Oversight i 30 Stott Avenue Northeast Nuclear Energy Company i Norwich, CT 06360 P. O. Box 128 Waterford, CT 06385 Mr. Mr. K. Thayer Recovery Officer - Nuclear Engineering and Support Northeast Nuclear Energy Company P. O. Box 128 Waterford, Connecticut 06385 i

s a

2 Northeast Nuclear Energy Company Millstone Nuclear Power Station i' Unit 3 cc:

Deborah Katz, President Citizens Awareness Network P. O. Box 83 Shelburne Falls, MA 03170  :

Senior Resident Inspector Millstone Nuclear Power Station -

c/o U.S. Nuclear Regulatory '

Commission P. O. Box 513 Niantic, CT 06357 i

Mr. Allan Johanson, Assistant Director Office of Policy and Management '

Policy Development and Planning Division 450 Capitol Avenue - MS# 52ERN P. O. Box 341441 Hartford, CT 06134-1441 Citizens Regulatory Commission ATTN: Ms. Susan Perry Luxton 180 Great Neck Road Waterford, Connecticut 06385 l

The Honorable Terry Concannon  :

Co-Chair .

Nuclear Energy Advisory Council Room 4035 Legislative Office Building Capitol Avenue

• Hartford, Connecticut 06106 Mr. Evan W. Woo 11acott i Co-Chair Nuclear Energy Advisory Council 128 Terry's Plain Road  ;

Simsbury, Connecticut 06070 Little Harbor Consultants, Inc.

Millstone - ITP0P Project Office P. O. Box 0630 Niantic, Connecticut 06357-0630 Mr. B. D. Kenyon President and Chief Executive Officer  !

. Northeast Nuclear Energy Company  !

P. O. Box 128 Waterford, CT 06385 i

l.

{f. RE00EST FOR ADDITIONAL INFORMATION -

EROSION OF CEMENT FROM POROUS CONCRETE SUBFOUNDATIONS MILLSTONE NUCLEAR POWER STATION. UNIT 3 (

l TAC M96402

1. Construction Technology Laboratory (CTL) has performed a detailed  !

evaluation and attempted to identify the potential causes of (1) the '

erosion of high-alumina cement (HAC) from the upper porous concrete layer and (ii) the leaching of alkalles from the lower Portland cement porous concrete layer. However, it has neglected to consider one important aspect of erosion that is specific to the site condition. l During the placement of the Portland cement concrete basemat, the HAC i porous concrete and the seal coat were subjected to water accumulation i and high heat of hydration (necessary conditions for high rate of conversion). Conversion of HAC is likely to have started from that point on. Neglecting this initial condition is likely to yield an erroneous estimate of the degree of conversion and reduction in the compressive strength. Explain how this aspect of the porous concrete degradation is considered in your assessment.

2. In Reference 1, CTL emphasizes a need to have representative porous ,

concrete cores from the structure before it can provide a realistic l assessment of the actual condition of the concrete (degree of conversion of high alumina concrete, effects of alkalies, reduction in compressive strength,etc.).. Provide information regarding this planned activity, and results of CTL's final assessment.

3a. In the settlement analysis (Section 4 of Reference 2), GEI Consultants, Inc. (GEI) hypothesizes that all cements are lost prior to placing the static loading of the containment structure. This is a highly unrealistic initial condition. Discuss how you plan to use CTL's final assessment with GEI's techniques to obtain a realistic assessment of the settlement of the containment structure.

3b. CTL has made a rough first order estimate that the compressive strength of the HAC porous concrete will be reduced by 380 psi in the next 5 years. Explain if, and how, you_ accounted for this strength loss in your final assessment of the foundation behavior (e.g., in the estimate of moments and shears in the foundation basemat caused by uniform and differential settlements).

3c. Section 4.3.2 (Reference 2) states that EQE International, Inc. (EQE),

determined a maximum compressive stress of about 7.4 ksf on the porous concrete layer due to vertical seismic acceleration and due to overturning. Provide the minimum compressive stress and discuss whether  ;

or not there is any loss of contact on the circumference of the basemat. i 3d. Section 4.4 (Reference 2) states that total settlement of the 19-inch- l thick porous concrete layer due to complete loss of cement, static  ;

loading by the containment, and seismic loading (under safe shutdown Enclosure

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earthquake) is estimated to be about 1.7 inches. Does your estimate of l settlemer.ts consider the effect of saturation of the crushed stone with j l water? What is the estimated maximum differential settlement of the {

l basemat due to the factors mentioned in 3b and 3c above, and what are  !

! the consequences of such differential settlement?

} 3e. In conjunction with the assessment of settlements that could have i

occurred (prior to placement of the Initial Structural Integrity Testing i (ISIT) markers), and future prediction (including that under the l-postulated seismic event), provide a discussion of actions that you would take to ensure the integrity of the safety-related structures, i systems, and components affected by the potential. settlement. Such I 4

actions may include monitoring of differential settlements, identifying i critical areas where differential settlements need 'to be monitored, etc. ,

) '

i 4. The sketch of the Reactor Building structural model shown in Figure 3.4 i

(Reference 2) shows different notations for some.of the structural j clements from those shown in Figure 3.78-9 of the Final Safety Analysis

! Report (FSAR). Explain the differences, if any, between the structural 1

element models used in the FSAR and in the current soil-structure

! interaction analysis (Reference 2).

i

References:

1

! 1. Construction Technology Laboratory (CTL), " Investigation of Possible

! Deteric ation of Porous Concrete, Millstone 3," April 11,1997. Report attached to April 30, 1997, letter from M. H. Brothers, Northeast' Nuclear Energy company, to NRC.

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2. GEI Consultants, Inc.,_" Porous Concrete Investigation, Millstone 3, l

! March 14, 1997." Report attached to April 30, 1997,Eletter from

M. H. Brothers, Northeast Nuclear Energy Company,.to NRC.

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