ML13322B178
| ML13322B178 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/06/1990 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TASK-3.D.3.4, TASK-TM NUDOCS 9007110087 | |
| Download: ML13322B178 (3) | |
Text
Southem California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F. R. NANDY TELEPHONE MANAGER OF NUCLEAR LICENSING July 6, 1990 (714) 587-5400 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 inform you that we will be delaying our response to the action items identified in your September 17, 1989 meeting summary regarding Control Room Habitability. This response will be delayed from June 30, 1990 until three months after the completion of the Cycle 11 refueling outage (approximately March 1991).
The reasons for this delay are discussed below.
During the independent review of the dose calculation, several issues were raised regarding the adequacy of the assumptions and methodology used in performing the analysis. Resolution of these issues may affect the calculation and the final design of the control room HVAC system. Additional engineering efforts will be necessary to resolve these issues.
Those items affecting the design of the control room HVAC modifications are:
Automatic Initiation Automatic Initiation into the Emergency Filtration Mode of the control room HVAC was not part of the design proposed to the NRC in our October 10, 1986 submittal. The most recent thyroid dose calculation indicated that automatic initiation was not necessary. However, as a result of the questions raised on the assumptions and methodology used in the dose assessment calculation, automatic initiation is being investigated.
9007110087 900706 PDR ADOCK 05000206 P
Document Control Desk July 6, 1990 Emergency Air Filtration Unit Flow Rate The design flow rate being considered in the conceptual design for the new emergency air filtration system may need to be reduced due to improvements made to the control room pressure boundary. Efforts are underway to evaluate this flow rate.
Those items affecting the calculational model are:
Iodine Reduction Factor The iodine reduction factor used in the dose calculation is being re evaluated to confirm that it is conservative for SONGS 1 use.
Recirculation Volume The recirculation volume used in the dose calculation is being re evaluated to verify that it is conservative. A conservative minimum volume will be verified so that a maximum value of post accident recirculation leakage concentration is used in the thyroid dose calculation.
Containment Leakage Rate An effort is currently underway to evaluate the containment leak rate assumption in an effort to further reduce the thyroid dose. This was not investigated earlier due to initial results that indicated this effort was not required to achieve an acceptable dose.
Containment Spray Iodine Removal Coefficient The Containment Spray Iodine Removal Coefficient is currently being evaluated to determine its potential impact on the dose calculation.
This was not investigated earlier due to initial results that indicated this effort was not required to achieve an acceptable dose.
Since a large amount of resources are being devoted to the Cycle 11 refueling outage, the efforts required to complete the calculation will have to be delayed. In order to prevent further revisions to the submittal schedule, we are providing a variable end date schedule coupled to the end of the Cycle 11 outage. The submittal date of approximately March 1991 still provides a minimum of 15 months to the start of the Cycle 12 refueling outage, when the Control Room HVAC modifications are to be implemented. We will therefore submit our responses to the NRC action items on this subject three months after the end of the Cycle 11 refueling outage.
Document Control Desk July 6, 1990 If you have any questions concerning this schedule, please feel free to call me.
Very truly yours, cc:
J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3