ML060940664
| ML060940664 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/13/2006 |
| From: | Catherine Haney Plant Licensing Branch III-2 |
| To: | Sheppard J South Texas |
| Thadani M, NRR/DLPM, 415-1476 | |
| References | |
| TAC MB9859 | |
| Download: ML060940664 (6) | |
Text
April 13, 2006 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483
SUBJECT:
SOUTH TEXAS PROJECT, UNIT 2 - RE: COMPLIANCE OF CONTROL ROOM HABITABILITY TO APPLICABLE REGULATORY REQUIREMENTS (TAC NO. MB9859)
Dear Mr. Sheppard:
In Generic Letter 2003-01 Control Room Habitability (GL-2003-01), the NRC staff states that, during the design of nuclear power plants, licensees performed analyses to demonstrate that the control room habitability systems (CRHSs), as designed, provide a habitable environment during postulated design basis events. These design analyses model the transport of potential contaminants into the control room envelope (CRE) and their removal. The amount of inleakage of assumed contaminants is important to these analyses, because unaccounted-for contaminants entering the CRE may impact the ability of the operators to perform plant control functions. If contaminants impair the response of the operators to an accident, there could be inadequate response to mitigate the impact of the accident consequences to the public health and safety.
Because of the importance of ensuring habitable control rooms under all normal and off-normal plant conditions, the addressees of GL-2003-01 were asked to provide confirmation that their facilitys control room meets the applicable habitability regulatory requirements and that the CRHSs are designed, constructed, configured, operated, and maintained in accordance with the facilitys design and licensing bases. The NRC staff specifically requested the addressees to confirm that the most limiting unfiltered inleakage (and the filtered inleakage if applicable) into their facilitys CRE was no more than the value assumed in their design basis radiological analyses for control room habitability and incorporated into their hazardous chemical assessment, and that reactor control could be maintained from either the control room or the alternate shutdown panel in the event of evolution of smoke. Licensees were also requested to describe how and when they performed the analyses, tests, and measurements for this confirmation.
In a letter dated August 5, 2004, South Texas Project Nuclear Operating Company (STPNOC) provided the results of an integrated tracer gas test conducted at South Texas Project (STP),
Unit 1, during the week of March 8, 2004. To date, Unit 2 has not been tested. It is STPNOCs position that it is sufficient to test only the Unit 1 CRE, since inleakage of the Unit 2 CRE can be inferred from the results of the Unit 1 test because the two unit's CREs are identical in terms of design, materials, and construction. Therefore, because STPNOC asserts that the two reactors and their associated balance of plant designs are identical, STPNOC believes the two CREs performances of inleakage would be identical.
J. Sheppard It is the NRC staffs experience, that structures (i.e. CREs) that are designed and constructed of the same materials by the same company with similar components rarely demonstrate identical inleakage performance. This is especially true with respect to inleakages measured during tests. For example, potential sources of CRE inleakage include the walls, floors, ceilings, ductwork that passes through the envelope, intake and exhaust dampers and ductwork of the CRE ventilation system, fans, filter housing, instrument air lines, and electrical penetrations. CRE inleakage is a function of the differential pressure gradient across the boundary of the envelope, where inleakage results from respective penetrations in the envelope. In order for two CREs to have identical inleakage characteristics, each of the two CREs should demonstrate identical differential pressure gradients at similar locations across the penetrations in the two CREs. With different heat generation and removal rates within the CRE and areas adjacent to the CRE, it is unlikely that this can be demonstrated. In order to assure identical performance, the redundant equipment must also perform in an identical manner. Experience has shown that, typically, there is a significant variation in the inleakage performance of redundant trains of ventilation equipment. This was evident in the STPNOC testing performed on STP, Unit 1, as discussed next.
STPNOCs letter dated August 5, 2004, provided test results from tracer gas testing performed at STP, Unit 1, during the week of March 8, 2004. The design of the control room emergency ventilation systems for Units 1 and 2 is based on three 50 percent trains serving the same control room. The possible inleakage test result configurations for Unit 1 as reported are:
Trains A & B 9.4+/-50 cfm Trains A & C
-27+/-50 cfm Trains B & C 1.9+/-25 cfm Note that the three trains of the same system serving the same CRE do not have identical inleakage results. The NRC staff expects that, if three trains in a different CRE were tested, it is unlikely that the results would be similar to the results obtained for Unit 1 and, in fact, it would be more likely that the results would be different and could be greater than the results for Unit 1. There are numerous reasons why differences exist. Some differences are based upon the buildings of interest having different locations or different orientations. Some other differences are attributed to reactors balance-of-plant designs exhibiting different performance characteristics.
A review of plants' technical specifications shows that it is not acceptable to rely upon the test results from one train when the design consists of redundant trains. The staff finds that both trains need to be tested. Consequently, it is reasonable that all CREs should be tested even if they are considered to be identical in construction.
Therefore, contrary to STPNOCs position, the NRC staff concludes that Unit 2 should be tracer gas tested to determine CRE inleakage. As discussed above, the staffs conclusion is based upon the results of the Unit 1 tests and the Unit 1 and Unit 2 differential pressure measurements, testing results from other CREs, and current technical specification requirements for redundant trains.
J. Sheppard If you have any questions please contact the NRC Project Manager, Mohan Thadani at (301) 415-1476.
Sincerely,
/RA/ Cornelius Holden for Catherine Haney, Director Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-499 cc: See next page
J. Sheppard If you have any questions please contact the NRC Project Manager, Mohan Thadani at (301) 415-1476.
Sincerely,
/RA/ Cornelius Holden for Catherine Haney, Director Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-499 cc: See next page DISTRIBUTION PUBLIC LPLIV Reading RidsNrrDorl RidsNrrDorlLplg RidsNrrPMMThadani RidsNrrLADJohnson RidsNrrDorlDpr RidsOgcRp RidsAcrsAcnwMailCenter RidsRgn4MailCenter RDennig HWalker JHayes ACCESSION NO:
OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/LPL4/BC NRR/DORL/D NAME MThadani;sem2 DJohnson DTerao CHaney (CHolden for)
DATE 4/12/06 4/12/06 4/12/06 4/13/06 OFFICIAL RECORD COPY
South Texas Project, Units 1 & 2 cc:
Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 910 Bay City, TX 77414 C. Kirksey/C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 Mr. J. J. Nesrsta Mr. R. K. Temple City Public Service Board P. O. Box 1771 San Antonio, TX 78296 INPO Records Center 700 Galleria Parkway Atlanta, GA 30339-3064 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Steve Winn Texas Genco, LP 12301 Kurland Drive Houston, TX 77034 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414 A. H. Gutterman, Esq.
Morgan, Lewis & Bockius 1111 Pennsylvania Avenue, NW Washington, DC 20004 E. D. Halpin Vice President Oversight STP Nuclear Operating Company P. O. Box 289 Wadsworth, TX 77483 S. M. Head, Manager, Licensing STP Nuclear Operating Company P. O. Box 289, Mail Code: N5014 Wadsworth, TX 77483 Environmental and Natural Resources Policy Director P. O. Box 12428 Austin, TX 78711-3189 Jon C. Wood Cox, Smith, & Matthews 112 East Pecan, Suite 1800 San Antonio, TX 78205 Director Division of Compliance & Inspection Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756 Brian Almon Public Utility Commission William B. Travis Building P. O. Box 13326 1701 North Congress Avenue Austin, TX 78701-3326 Susan M. Jablonski Office of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087 Mr. Terry Parks, Chief Inspector Texas Department of Licensing and Regulation Boiler Division P. O. Box 12157 Austin, TX 78711 Mr. Ted Enos 4200 South Hulen Suite 630 Ft. Worth, Texas 76109