ML13330B552
| ML13330B552 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/05/1991 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TASK-3.D.3.4, TASK-TM NUDOCS 9109060187 | |
| Download: ML13330B552 (3) | |
Text
Southern Caifornia Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 R. M.
ROSENBLUM TELEPHONE MANAGER OF (714) 454-4505 NUCLEAR REGULATORY AFFAIRS September 5, 1991 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 TMI Item III.D.3.4 Control Room Habitability San Onofre Nuclear Generating Station, Unit 1 The purpose of this letter is to revise the schedule for submittal of additional information regarding Control Room Habitability open items that was provided in our June 25, 1991 letter. We recently received additional NRC guidance for the calculation of atmospheric dispersion factors and intend to incorporate this guidance into our revised radiological dose assessments.
There have also been some changes to the Control Room Habitability design. As a result, it will be necessary to reschedule our Control Room Habitability submittals. This letter also provides our evaluation of the use of ANSI N509 code instead of ASME AG-1 code for applications in our proposed upgrades to the control room HVAC system.
REVISED SUBMITTAL SCHEDULE During a July 19, 1991 telephone conversation, the NRC staff provided us with additional guidance for modeling atmospheric dispersion in accordance with NUREG/CR-5055. We intend to use this guidance to evaluate the control room operator thyroid dose to each shift and the whole body dose. The outcome of these evaluations will be used in our evaluation of the requirements for use of Self Contained Breathing Apparatus (SCBA). To incorporate the new NRC guidance, we need to reschedule our submittal of the whole body dose and thyroid dose to each shift and the SCBA evaluation. The submittal date for these items will be November 22, 1991.
We had committed to submit an evaluation of the procedures for notifying control room operators to put the emergency HVAC system into operation in the event of a fuel handling accident or a waste gas system accident. We had also committed to submit an evaluation of the ammonia concentration in the control room if manual isolation of the HVAC system occurs at two minutes. Subsequent to our letter, as part of final engineering to evaluate our Control Room Habitability design, it was determined that additional efforts are required.
Therefore, it is necessary to revise the submittal date for these items to November 22, 1991.
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-2 additional efforts are required. Therefore, it is necessary to revise the submittal date for these items to November 22, 1991.
Our submittal of the offsite toxic gas hazards evaluation that was scheduled for September 27, 1991 will be postponed. Originally we had planned to update the analysis by using the latest highway survey and compare the risk from each chemical individually with the Regulatory Guide 1.78 limits. However, we have reevaluated our application of the Standard Review Plan (SRP) 2.2.3 guidelines to toxic gases. Unlike our previous analysis, we intend to sum the contributions from all relevant toxic material events and to apply the SRP guidelines to the resultant aggregate toxic gas risk. This approach would require us to reassess some chemicals that were previously excluded from posing a risk to the plant based on the extremely low probability that each individual chemical would impact the control room. We are still evaluating the scope of this effort and will provide you with a revised schedule by November 22, 1991.
EVALUATION OF COMPLIANCE WITH ASME AG-1 CODE During an April 11, 1991 meeting with the NRC we indicated that our upgrades to the Control Room HVAC System would be in accordance with ANSI N509-1989.
The NRC requested that the proposed upgrades comply with ASME AG-1 requirements which codifies ANSI N509. We have reviewed the requirements of ASME AG-1, through the 1990 addenda, as they apply to the Control Room and the Technical Support Center (TSC) HVAC systems. Three sections of ASME AG-1, Ductwork, Prefilters, and Instrumentation and Controls, are under development and are not available. Two sections of ANSI N509-1989, Adsorbers, and Adsorbent Material refer specifically to ASME AG-1. There are relatively minor technical differences between the remaining sections of ASME AG-1 and ANSI N509.
ASME AG-1 requires that a more detailed analysis be performed for HVAC components and ducting to determine the allowable loading combinations.
ANSI N509 is based on generic allowables for stress and deflection which are more conservative than ASME AG-1. In addition, ASME AG-1 restricts the use of similarity analysis for seismic qualification. Consequently, components that are too complex to be analyzed will require a combination of analysis and testing to meet the requirement. The code also requires material certification and more stringent functional testing for components.
Implementing ASME AG-1 instead of ANSI N509 would significantly increase the cost of the upgrades by increasing the documentation and testing requirements without enhancing the HVAC component design.
If we were designing an entirely new HVAC system, the use of ASME AG-1 might be appropriate. Since we are upgrading only portions of the Control Room and the TSC HVAC systems, using ASME AG-1 instead of ANSI N509 would not be practical.
Based on the results of our evaluation, using ANSI N509 provides.
Document Control Desk
-3 an acceptable conservative design. Also, ANSI N509 is consistent with Regulatory Guide 1.52 guidance. Therefore, SCE will continue to design the Control Room and TSC HVAC in accordance with ANSI N509-1989.
If you have any questions regarding this information, please let me know.
Very truly yours, cc:
J. B. Martin, Regional Administrator, NRC Region V George Kalman, NRC Senior Project Manager, San Onofre Unit 1 J. 0. Bradfute, NRC Project Manager, San Onofre Unit 1 C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 & 3