ML20211D884
| ML20211D884 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 09/18/1997 |
| From: | Quay T NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9709290277 | |
| Download: ML20211D884 (3) | |
Text
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j NUCLEAR REGULATORY COMMISSION
%,*****/g WASHINGTON, D.o. 30666-0001 September 18, 1997 1
Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230
SUBJECT:
ULTIMATE CAPACITY OF AP600 CONTAINMENT
Dear Mr. Liparulo:
The Civil Engineering and Geosciences Branch (ECGB) has identified apparent weak elements in the ultimate capacity of the AP600's containment, they are the equipment hatch covers. The equipment hatch covers form a portion of the containment boundary.
Structurally, they act as an independent shell, and if they were to buckle due to internal accident pressure, it could provide a leakage path to the atmosphere. Thus, a failure of the hatch covers due to buckling could lead to radioactive leakage through the equipment hatch sleeve / gasket, thereby jeopardizing the leaktight integrity of the contain-ment.
The ECGB identified in the final safety evaluation report input that the 16-ft and 22-ft equipment hatch covers have a much weaker design capacity (ASME Service level C Limit of 62 psig and 76 psig respectively at 280 *F) when compared to the containment ellipsoidal head (ASME Service Level C Limit of 92 psig at 280 *F).
A simple addition of stiffeners to the hatch covers, or making the hatch covers thicker, can easily increase the overall contain-ment capacity to the next higher level of 92 psig at 280 'F.
The Commission approved the staff's position to use the deterministic contain-l/
ment performance goal, specified in SECY-93-087, as a complement to the
/0 probabilistic containment performance goal. The deterministic containment performance goal states that the containment should maintain its role as a pD3 reliable, leak-tight barrier (for example, by ensuring that containment stresses do not exceed ASME Service Level C limits for metal containments) for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following the onset of core damage under the more likely severe accident challenges.
For severe accidents sequences, involving failure of the passive containment cooling system or a hydrogen detonation, the pressure inside containment starts to exceed ASME Service Level C Limit approximately 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> after accident initiation and reaches up to 74.3 psig at 310 *F at the end of the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Because the failure modes of the passive containment cooling system are independent from those leading to core damage and the AP600 has a hydrogen igniter system, the staff cannot support the position that the more likely severe challenges should include sequences involving failure of the passive containment cooling system or a hydrogen detonation.
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a Mr. Nicholas J. Liparulo September 18, 1997 However, the staff is concerned about containment venting in the case of a internal pressurization that could challenge containment integrity. Although venting is not expected to be necessary in most severe accident sequences, it may be needed for some sequences.
For the evolutionary designs venting capability was provided which could be used to relieve containment pressure before containment pressure reached ASME Code Service level C.
The staff is concerned that, because of the limitations of the equipment hatches, this venting would take place at a relatively low pressure. The equipment hatch covers design could be revised to add stiffeners, or be made thicker, such that they no longer remain the weakest link. The staff believes that the cost to install these stiffeners, or to thicken the equi ment hatch covers, would be relatively low. Therefore, the staff requests t1at Westinghouse consider this option, and also that it provide an estimate of the cost to make the design more robust.
If you have any quertions regarding this mattar, you can contact Joseph Sebrosky at (301) 415-1132.
Sincerely, l
i original signed by:
Theodore R. Quay, Director Standardization Project Directorate Division of Reactor Program Management i
Office of Nuclear Reactor Regulation Docket No.52-003 cc: See next page.
DISTRIBUTIQH:
Docket File PDST R/F JRoe PUBLIC DMatthews TRQuay TKenyon BHuffman JSebrosky DScaletti JNWilson Slee, 0-7 H15 JMoore, 0-15 B18 WDean, 0-5 E23 ACRS (11)
GBagchi, 0-7 H15 JKudrick, 0-8 H7 RPalla, 0-8 H7 MSnodderly, 0-8 H7 DOCUMENT NAME: A:EQHATCH.POS
- See previous concurrence la retelve a copy of thle doewnent,indeste in the ben: *C* = Copy without attachmentlencloewe "E" = Copy with attachment / enclosure
- N* = No copy 0FFICE PM:PDST:DRPM l
SCSB:DSSA D:ECGB:DE D:PDST:DRPM l l
NAME JSebrosky:sg d0:'
JKudrick*
GBagchi*
TRQuay %
DATE 09//P/97 il 09/18/97 09/18/97 09/ W/97 0FFICIAL RECORD COPY
}
Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Mr. Russ Bell Advanced Plant Safety & Licensing Senior Project Manager, Programs Westinghouse Electric Corporation Nuclear Energy Institute Energy Systems Business Unit 1776 I Street, NW P.O. Box 355 Suite 300 Pittsburgh, PA 15230 Washington, DC 20006-3706 Mr. Cindy L. Haag Ms. Lynn Connor Advanced Plant Safety & Licensing Doc-Search Associates Westinghouse Electric Corporation Post Office Box 34 Energy Systems Business Unit Cabin John, MD 20818 Box 355 Pittsburgh, PA 15230 Dr. Craig D. Sawyer, Manager Advanced Reactor Programs Mr. S. M. Modro GE Nuclear Energy Nuclear Systems Analysis Technologies 175 Curtner Avenue, MC-754 Lockheed Idaho Technologies Company San Jose, CA 95125 Post Office Box 1625 Idaho Falls, ID 83415 Mr. Robert H. Buchholz GE Nuclear Energy Mr. Sterling Franks 175 Curtner Avenue, MC-781 U.S. Department of Energy San Jose, CA 95125 NE-50 19901 Germantown Road Barton Z. Cowan Esq.
Germantown, MD 20874 Eckert Seamans Cherin & Mellott 600 Grant Street 42nd Floor Mr. Frank A. Ross Pittsburgh, PA 15219 U.S. Department of Energy, NE-42 Office of LWR Safety and Technology Mr. Ed Rodwell, Manager 19901 Germantown Road PWR Design Certification Germantown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Mr. Charles ~ Thompson, Nuclear Engineer Palo Alto, CA 94303 AP600 Certification NE-50 19901 Germantown Road Germantown, MD 20874