ML042650353
| ML042650353 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/17/2004 |
| From: | Scherer A Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-03-001 | |
| Download: ML042650353 (5) | |
Text
'4 SOUTHERN CALIFORNIA A. Edward Scherer EDISON?
Manager of September 17, 2004 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D.C. 20555
Subject:
Docket Nos. 50-361 and 50-362 Response to Generic Letter 2003-01, "Control Room Habitability" Tracer Gas Test Results San Onofre Nuclear Generating Station Units 2 and 3
References:
- 1.
NRC Generic Letter 2003-01, "Control Room Habitability," dated June 12, 2003
- 2.
Letter from A. E. Scherer (SCE) to Document Control Desk (NRC), dated August 5, 2003,
Subject:
Docket Nos. 50-361 and 50-362, Response to Generic Letter 2003-01, Control Room Habitability, San Onofre Nuclear Generating Station, Units 2 and 3
- 3.
Letter from Eric J. Leeds (NRC) to James W. Davis (NEI), dated January 30, 2004,
Subject:
NEI Draft White Paper, Use of the Generic Letter 91-18 Process and Alternative Source Terms in the Context of Control Room Habitability
- 4.
Nuclear Energy Institute (NEI) 99-03, Revision 1, Control Room Habitability Guidance, dated March 2003
Dear Sir or Madam:
This letter provides the results of Control Room Envelope (CRE) Inleakage Testing performed at San Onofre Units 2 and 3 during May of 2004.
Generic Letter (GL) 2003-01, Control Room Habitability, (Reference 1) requested that licensees provide confirmation that 1) the control room meets the applicable habitability regulatory requirements (e.g., GDC 1, 3,4, 5, and 19) and 2) the Control Room Habitability Systems (CRHSs) are designed, constructed, configured, operated, and maintained in accordance with the design and licensing bases. Reference 1 requested that emphasis be placed on 1) the amount of unfiltered inleakage assumed in radiological analyses, 2) the amount of unfiltered inleakage assumed in hazardous chemical assessments, and 3) the ability of Technical Specifications (TSs) Surveillance Requirements to verify that the assumed inleakage rates are valid.
P.O. Box 128 San Clemente, CA 92674-0128 949-368-7501 Fax 949-368-7575
Document Control Desk September 17, 2004 Southern California Edison (SCE) provided a 60-day response to GL 2003-01 on August 5, 2003 (Reference 2). Reference 2 provided information regarding the amounts of control room inleakage assumed in radiological analyses and hazardous chemical assessments. Reference 2 also provided a commitment to perform CRE inleakage testing prior to the Unit 3 Cycle 13 Refueling Outage, and to provide the results of the testing to the NRC.
CRE Inleakage Testing Reference 1 requested that licensees confirm that the most limiting inleakage into the CRE is less than the values assumed for design basis radiological and hazardous chemical analyses. Reference I refers to ASTM E-741, "Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution," as an example of an acceptable test methodology.
SCE contracted with Lagus Applied Technologies (LAT) to perform CRE inleakage testing. This testing, based on ASTM E-741 methodology, was performed at San Onofre Units 2 and 3 in May of 2004.
Test Configurations San Onofre Units 2 and 3 have a shared control room. The Control Room Emergency Air Cleanup System (CREACUS) is a dual train system that has the capability of operating in emergency mode or isolation mode.
The CREACUS emergency mode is a pressurized mode that is initiated during radiological events. As described in Reference 2, during operation in the emergency mode of CREACUS, the San Onofre Units 2 and 3 design basis radiological analyses assume 10 cubic feet per minute of unfiltered inleakage into the Control Room Envelope (CRE) due to ingress and egress. This assumption implies that, due to control room pressurization, no other source of filtered or unfiltered inleakage into the control room envelope exists.
The CREACUS isolation mode is a neutral pressure mode that is initiated during hazardous chemical events. Reference 2 describes the current limiting value for CRE inleakage in design basis hazardous chemical analyses as 2,201.3 CFM.
The CRE inleakage was measured with CREACUS operating in two emergency (pressurization) modes (A Train, B Train) and two isolation modes (A Train, B Train).
To ensure that the most limiting case was tested, a fifth case was also measured. In order to maximize CRE inleakage, this fifth test was performed on Train B of CREACUS in the isolation mode with a normal supply fan turned off and normal exhaust fans running to create a differential pressure across the CRE. This test mode is hereafter referred to as Isolation Mode (High AP).
Document Control Desk September 17, 2004 Test Methods Unfiltered air inleakage rates into the CRE with the CREACUS in the emergency (pressurization) modes were measured using a Makeup FlowratelConcentration Decay Test, based on the methodology described in ASTM Standard E-741. Air inleakage rates into the CRE with the CREACUS in the isolation mode were measured using a Tracer Concentration Decay Test, based on the methodology described in ASTM E-741. Exceptions to implementation of ASTM E-741 were taken in the development of the test protocol. These exceptions are identical to those listed in Nuclear Energy Institute (NEI) 99-03, Revision 1, "Control Room Habitability Guidance," Informational Appendix EE.
Results The results of the CRE inleakage testing are summarized as follows:
Item Result scfm A Train Pressurization Mode Inleakage 67 B Train Pressurization Mode Inleakage 65 A Train Isolation Mode Inleakage 645 +/-17 B Train Isolation Mode Inleakage 468 +/-11 B Train Isolation Mode (High AP) Inleakage 604 +15/-16 The results for the two Pressurization Mode tests are presented without uncertainty values. Consistent with Regulatory Guide 1.197, "Demonstrating Control Room Envelope Integrity At Nuclear Power Reactors," Section 1.4, consideration of uncertainty is unnecessary when the inleakage rate is demonstrated to be below 100 CFM.
The A Train and B Train Pressurization Modes were tested individually. Dual train testing was not performed due to an assumption that the higher control room pressure resulting from both trains running together would result in less unfiltered inleakage.
However, the test results suggest that nearly all of the unfiltered inleakage may originate from low-pressure ducting associated with the A and B Train control room cabinet area coolers. As the cabinet coolers are part of the CREACUS, the test results indicate the potential for greater unfiltered inleakage with both trains running. The maximum dual train unfiltered inleakage would be no more than 132 CFM, representing the sum of the A Train and B Train unfiltered inleakage rates. The uncertainty for these measurements is +/- 127 CFM. Consistent with Regulatory Guide 1.197, consideration of uncertainty indicates a maximum dual train operation unfiltered inleakage rate of 259 CFM.
Document Control Desk September 17, 2004 Operabilitv of the Control Room EnveloDe The results for the Train A and Train B Isolation mode tests, as well as the Isolation Mode (High AP) test, are within the test acceptance criteria.
The results for the Train A and Train B Pressurization mode tests are greater than the values used in the design basis radiological analyses. Therefore, it is necessary to determine operability of the CRE. Reference 3 provided NRC comments on the use of Alternative Source Term (AST) methodology for Operability Assessments. Reference 3 stated that, subject to limitations, if CRE unfiltered inleakage is shown by Tracer Gas Testing to be greater than the amount assumed in the licensing basis radiological consequence analyses, the licensee may use AST analytical methods in performing its operability determination to verify that the control room ventilation system can accomplish its specified safety function. One limitation identified is that a licensee must ensure that results of analysis performed using AST analytical methods are expressed in a manner consistent with its current licensing basis acceptance criteria for control room habitability. A licensee that desires to use AST methodology in operability determinations must calculate whole body and critical organ doses for comparison with its current licensing basis acceptance criteria.
The current licensing basis acceptance criteria for San Onofre Units 2 and 3 are control room doses of no more than 30 Rem thyroid, 30 Rem beta skin, and 5 Rem whole body gamma. These criteria are consistent with 10 CFR Part 50 Appendix A General Design Criterion (GDC) 19.
Using AST methodology and the current licensing basis acceptance criteria described above, SCE has determined that the maximum amount of CRE unfiltered inleakage that would be consistent with an OPERABLE CRE is greater than the unfiltered inleakage that has been demonstrated by CRE unfiltered inleakage testing. Therefore, the CRE is non-conforming, but OPERABLE.
In order to restore the CRE to full qualification, corrective action is necessary. SCE intends to submit a Ucense Amendment Request to change the accident source term for San Onofre Units 2 and 3 to an AST. Design basis radiological consequence analyses to support this License Amendment Request will show that acceptable dose consequences are obtained using an assumed CRE unfiltered inleakage of 1000 CFM (including the 10 CFM allowance for ingress and egress). This License Amendment Request is currently in preparation and will be submitted by December 31, 2004.
Document Control Desk September 17, 2004 If you have any question or require additional information, please contact Mr. Jack Rainsberry at 949-368-7420.
Sincerely, cc:
B. S. Mallett, Regional Administrator, NRC Region IV B. M. Pham, NRC Project Manager, San Onofre Units 2, and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 & 3