ML20151L804
| ML20151L804 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/04/1997 |
| From: | Alexion T NRC (Affiliation Not Assigned) |
| To: | Cottle W HOUSTON LIGHTING & POWER CO. |
| References | |
| TAC-M98914, TAC-M98915, NUDOCS 9708070221 | |
| Download: ML20151L804 (5) | |
Text
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August 4, 1997 Mr. William T. _ Cottle Executive Vice-President &
General Manager, Nuclear
' Houston Lighting & Power Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX. 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING REVISED MAIN STEAM LINE BREAK (MSLB) ANALYSIS, SOUTH TEXAS PROJECT, UNITS 1 AND 2 (STP) (TAC NOS. M98914 AND M98915)
Dear Mr. Cottle:
.By letter dated December 17, 1996, Houston Lighting & Power Company (HL&P) provided its 10 CFR 50.59 Summary Report. Unreviewed Safety Question Evaluation (USQE) #95-013, regarding the revised mass and energy release MSLB analysis, was one of several USQEs from the Summary Report that the Nuclear Regulatory Commission (NRC) staff selected for further review.
Upon notification that USQE #95-013 was selected for further review, HL&P promptly provided the USQE #95-013 document.
]
The NRC staff is reviewing the_USQE #95-013 document and has identified additional information that is needed.
It is requested that you provide the additional information within 30 days from the date of this letter.
Sincerely, Original signed b Thomas W. Alexion,yProject Manager Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
Request For Additional Information cc w/ enc 1: See next page DISTRIBUTION:
Docket File PUBLIC PD4-1 r/f ACRS JRoe EAdensam (EGAl)
JClifford TGwynn, RIV CHawes TAlexion 0GC Document Name:
STP98914.LTR OFC PM/PDFd LA/PD4-1 CDI l
NAME TAlexio CHawes&R)d DATE [/h97
'1/29/97 fYES)NO YES/N0 COPY 0FilCIAL RECORD COPY alHC flLE CFJ7ER COPY a'
9708070221 970004 h0
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UNITED CTATES
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NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 20666 4 001
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August 4,1997 Mr. William T. Cottle Executive Vice-President &
General Manager, Nuclear Houston Lighting & Power Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING REVISED MAIN STEAM LINE BREAK (MSLB) ANALYSIS, SOUTH TEXAS PROJECT, UNITS 1 AND 2 (STP) (TAC NOS. M98914 AND M98915)
Dear Mr. Cottle:
By letter dated December 17, 1996, Houston Lighting & Power Company (HL&P) provided its 10 CFR 50.59 Summary Report. Unreviewed Safety Question Evaluation (USQE) #95-013, regarding the revised mass and energy release MSLB analysis, was one of several USQEs from the Summary Report that the Nuclear Regulatory Commission (NRC) staff selected for further review. Upon notification that USQE #95-013 was selected for further review, HL&P promptly provided the USQE #95-013 document.
The NRC staff is reviewing the USQE #95-013 document and has identified additional information that is needed.
It is requested that you provide the additional information within 30 days from the date of this letter.
i Sincerely,
$<fyylg) s Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
Request For Additional Information cc w/ enc 1: See next page
I
)
Mr. William T. Cottle Houston Lighting & Power Company South Texas, Units 1 & 2 l
i cc:
E Mr. David P.. Loveless Jack R. Newman, Esq.
l Senior Resident Inspector Morgan, Lewis & Bockius U.S. Nuclear Regulatory Commission 1800 M Street, N.W.
P. O. Box 910 Washington, DC 20036-5869 l'
Bay City, TX 77414
)
Mr. Lawrence E. Martin f
Mr. J. C. Lanier/M. B. Lee General Manager, Nuclear Assurance Licensing City of Austin Houston Lighting and Power Company Electric Utility Department P. O. Box 289 721 Barton Springs Road Wadsworth, TX 77483 l
i Austin, TX 78704 l-Rufus S. Scott j
Mr. M. T. Hardt Associate General Counsel Mr. W. C. Gunst Houston Lighting and Power Company City Public Service Board P. O. Box 61867 P. O. Box 1771 Houston, TX 77208 San Antonio, TX 78296 Joseph R. Egan,.Esq.
Mr. G. E. Vaughn/C. A. Johnson Egan & Associates, P.C.
Central Power and Light Company 2300 N Street, N.W.
P. O. Box 289 Washington,-DC.20037 Mail Code: N5012 Wadsworth, TX 74483 Office of the Governor ATTN: Andy Barrett, Director INPO Environmental Policy Records Center P. O. Box 12428 700 Galleria Parkway Austin, TX 78711 Atlanta, GA 30339-3064 1
Arthur C. Tate, Director
-Regional Administrator, Region IV-DivisiDn of Compliance & Inspection U.S. Nuclear Regulatory Commission Bureau of Radiation Control 611 Ryan Plaza Drive, Suite 400 Texas Department of Health Arlington, TX 76011 1100 West 49th Street Austin, TX 78756 Dr. Bertram Wolfe 15453 Via Vaquero Texas Public Utility Commission Monte Sereno, CA 95030 ATTN: Mr. Glenn W. Dishong 7800 Shoal Creek Blvd.
Judge, Matagorda County Suite 400N Matagorda County Courthouse Austin, TX 78757-1024 1700 Seventh Street Bay City TX 77414
- i..
l REQUEST FOR ADDITIONAL INFORMATION' REVISED MAIN STEAM LINE BREAK (MSLB) ANALYSIS SOUTH TEXAS PROJECT. UNITS I AND 2 DOCKET NOS. 50-498 AND 50-499 In response to Information Notice 93-55, HL&P performed in-house analyses of the Reactor Containment Building (RCB) and Isolation Valve Cubicle (IVC) pressure responses to a MSLB. HL&P's studies resulted in Justification for Continued.0peration (JCO) 93-0004 and Station Problem Report (SPR) 93-2415, when HL&P found that the original mass aad energy release analysis for the MSLB blowdown model for the IVC does not account for the moisture carry-over from the steam generators and may, therefore, be nonconservative. HL&P identified two nonconservative assumptions in the MSLB mass and energy release analyses:
(1) a full power initial condition was assumed rather than hot zero power, and (2) only the steam release from the faulted steam generator (SG) was considered (backflow from the three intact SGs and the main steam piping was neglected).
From HL&P's RETRAN-02 (mass and energy) and GOTHIC (subcompartment) analyses HL&P made the following findings:
For IVC short-term peak pressure: HL&P determined that based on a conservative (bounding) mass and energy release for the hot zero power condition with the main steam isolation valves (MSIVs) open, and using new dynamic load factors to amplify the pressure peaks, the IVC blowout panels might not be capable of relieving pressure quickly enough to prevent overstress by as much as 10% in the limiting IVC node. HL&P subsequently determined that the overstress condition is. acceptable because of (1) load redistribution to other structural members and (2) the actual strength of the concrete exceeds the design strength.
For RCB short-term peak pressures: HL&P found that the short-term peak pressure is slightly greater than that originally calculated by Bechtel,
~
but within existing margin.
For IVC long-term peak pressure: HL&P found that the calculated peak pressures exceed the short-term peak pressures.
For the limiting node, the calculated peak pressure was less than the original Bechtel peak and was found acceptable.
For RCB long-term peak pressure: The Nuclear Regulatory Commission staff is confused by two apparently conflicting statements. The last sentence of the first paragraph of JC0 93-0004, Section 4.5 states, "The analysis of the long-term response with moisture carryover for the limiting subcompartments shows that the calculated pressures in the IVC
& RCB exceeded the peak pressure for the short-term analysis." The second-to-last sentence of Section 4.5 states, "...the peak pressure differential between the main containment subcompartment and break subcompartment is less for the long-term response than the short-term ENCLOSURE
r 1 1 I
response." HL&P's JC0 concluded that the RCB long-term response is acceptable because it is bounded by the short-term response. Please i
clarify (the short-term response cannot bound the long-term response if the long-term response exceeds the short-term response)!
Also, in reviewing JC0 93-0004 and SPR 93-2415 documentation, additional questions have arisen. The staff is concerned that similar deficiencies may exist at other facilities that may not have been identified by licensees in j
the course of their Information Notice 93-55 assessments.
In addition to clarification of the RCB long-term response, other items for which the staff seeks additional information include:
1.
Are different mass and energy release methodologies used for MSLB 1
subcompartment peak pressure analyses inside containment vs.
outside containment?
2.
HL&P's JC0 93-0004 and SPR 93-2415 documentation indicates that 1
the original dynamic load factors were nonconservative. Discuss the root cause/ differences between the original and new Sargent &
Lundy dynamic load factors.
i 3.
The new IVC node pressure curves appear to have been run for a period of 20 seconds.
Is HL&P confident that this is sufficient to identify the peak pressure?
4.
What spectrum of break sizes was analyzed for (a) the IVC piping subject to " break exclusion," and (b) the IVC piping not subject d
to break exclusion.
1 5.
Was any reanalysis performed with respect to the overall containment peak pressure for a MSLB (or was the effort limited to j
subcompartment analyses)?
,