ML13330A291
| ML13330A291 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/13/1981 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13330A293 | List: |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TAC-44128, TASK-2.E.4.2, TASK-3.D.3.4, TASK-TM NUDOCS 8104150153 | |
| Download: ML13330A291 (9) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING, April 13, 1981 (213) 572 1401 SAFETY, AND LICENSING Director, Office of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 Clarification of TMI Action Plan Requirements San Onofre Nuclear Generating Station Unit 1 Your letter dated October 31, 1980 forwarded NUREG-0737 containing all TMI-related items approved for implementation by the Commission at that time. You requested that we provide confirmation that the implementation dates for all items contained in NUREG-0737 will be met or propose revised dates with justification for delay and planned compensating safety actions during the interim. Our January 5, 1981 letter indicated that information required by Action Plan Items II.E.4.2(5), Containment Isolation Dependability, and III.D.3.4, Control Room Habitability, would be provided by April 1, 1981 rather than January 1, 1981 as contained in NUREG-0737.
The purpose of this letter is to provide the requested information on the aforementioned TMI Action Plan Items.
The requested information is discussed below:
Action Plan Item II.E.4.2(5):
Containment Isolation Dependability This Action Plan Item requires that the containment setpoint pressure that initiates containment isolation be reduced to the minimum compatible with normal operating conditions. The current containment setpoint pressure that initiates containment isolation is 2.0 psig. The normal operating pressure in the San Onofre Unit 1 containment varies from slightly negative to a few tenths of a pound positive pressure. Therefore, the current Technical Specifications permit continued operation up to a maximum containment pressure of 0.4 psig. Based on existing margins to preclude spurious isolation, we have determined that the containment setpoint pressure that initiates containment isolation can be reduced to 1.4 psig or approximately 1 psig above the maximum allowable containment pressure during operation and slightly more than 1 psig above the normal operating conditions. The setpoint change will be made prior to return to power following the current outage.
810415053
D.
April 13, 1981 During our evaluation in connection with this TMI Action Plan Item, we determined that the "Containment Post Accident Pressure Reanalysis" submitted in January, 1977 assumed an initial condition of 0.0 psi-g containment pressure while the Technical Specifications currently permit continued operation with a maximum containment pressure of 0.4 psig. We are continuing to investigate this apparent discrepancy to determine the impact/consequences related to safe operation. Specifically, we are reviewing:
- 1. the "Containment Post Accident Pressure Reanalysis" to determine if an adequate margin might exist to accommodate an initial condition of 0.4 psig containment pressure without exceeding the calculated maximum peak containment pressure of 49.4 psig, and
- 2. the "Summary Sphere Stress Evaluation" submitted in conjunction with the "Containment Post Accident Pressure Reanalysis" in January, 1977 to determine if a higher calculated maximum peak containment pressure (i.e., 49.8 psig) would invalidate the conclusions made relative to code allowable stresses.
Preliminary results of our review of the "Containment Post Accident Pressure Reanalysis" indicate that an adequate margin may exist and that the calculated maximum peak containment pressure would not exceed 49.4 psig. In addition, preliminary results of our review of the "Summary Sphere Stress Evaluation" indicate that a containment internal pressure of 51 psig would still result in stresses within code allowable stresses.
We expect to complete our review as discussed above by April 24, 1981. If we conclude that the "Containment Post Accident Pressure Reanalysis" cannot accommodate the 0.4 psig as an initial condition without increasing the calculated maximum peak containment pressure of 49.4 psig and remedial action or corrective measures are required such as changes to the Technical Specifications, we will promptly notify the NRC Region V in accordance with the San Onofre Unit 1 Technical Specifications. As discussed above, even if the calculated maximum peak containment pressure were increased to 49.8 psig, the resulting stresses would still be within code allowable stresses.
Action Plan Item III.D.3.4: Control Room Habitability Requirements This Action Plan Item requires that assurance be provided that control room operators will be adequately protected against the effects of accidental releases of toxic and radioactive gases. Furthermore, where the control room does not meet current criteria, modifications must be made as necessary.
The control room habitability assessment for Sari Onofre Unit 1 is contained in the report entitled, "Control Room Habitability Evaluation, San Onofre Nuclear Generating Station, Unit 1 (NRC TMI Action Plan Item III.D.3.4) January 30, 1981," twenty copies of which accompany this letter. The information requested in Attachment 1 of the Action Plan Item in NUREG-0737 is incorporated into the enclosed report as Appendix A.
D.
April 13, 1981 As requested by this Action Plan Item, San Onofre Unit 1 has been reviewed against current control room habitability requirements. Enclosure 1 of this letter provides a comparison between San Onofre Unit 1 and the requisite requirements; and where we have determined San Onofre Unit 1 to be in noncompliance, we have included our plans to implement corrective actions or we have provided our basis for not complying. As discussed in Enclosure 1, we plan to replace the existing HVAC system. Based on conceptual engineering, the planned modifications will require approximately thirty months to complete. This implementation schedule consists of preliminary and final engineering time, an approximate eighteen month procurement lead time (from the completion of engineering) for required HVAC and filtration equipment and construction time. However, since the completion schedule can be impacted by the integrated assessment of potential modifications identified by review of station design and operation in connection with the SEP, such as seismic reevaluation, wind and tornado loading, offsite hazards, etc., or by the TMI Action Plan Item I.D.1, Control Room Design Review, approved for implementation in NUREG-0737, but currently awaiting the establishment of criteria and guidelines by the Regulatory staff, it is our intention to defer implementation of the planned modifications pending completion of the SEP and TMI Action Plan Item I.D.1.
For your information, an evaluation of offsite toxic gasses is not included.
Offsite toxic gas releases are being evaluated as part of the San Onofre Units 2 and 3 licensing review. A Safety Evaluation Report (SER) is expected to be issued by the NRC in May, 1981.
We plan to implement any necessary modifications at San Onofre Unit 1 which are identified in the NRC's SER as required to protect the San Onofre Units 2 and 3 control room operators. The implementation schedule for any modifications will be consistent with the schedule discussed above.
Our January 5, 1981 letter also indicated that the information requested by TMI Action Plan Item II.K.3.17, ECCS Outage Report, would be submitted by April 1, 1981.
The requested information has been compiled; however, the information has not been evaluated with respect to what changes, if any, may be appropriate to improve the availability of ECCS equipment. Our evaluation is expected to be submitted by April 20, 1981.
D.
April 13, 1981 If you have any questions or desire further information concerning the above material, please contact me.
Subscribed on this day of
, 1981.
ByJ
. P. Baskin Manager of Nuclear Engineering, Safety, and Licensing Sub ri Su and sworn,beor me this WTAWo JPZII day ofc 1981.
Not ry Public in and for the County of Lds Angeles, State of California Enclosures (2)
ENCLOSURE 1 COMPARISON BETWEEN SAN ONOFRE UNIT 1 AND REQUISITE REQUIREMENTS CONTROL ROOM HABITABILITY
- 1. Control Room Emergency Zone The reviewer checks to see that the zone includes the following:
- a. Instrumentation and controls necessary for a safe shutdown of the plant, i.e., the control room, including the critical document reference file.
Unit 1 meets this criteria. Critical documents are kept in the control room and the Technical Support Center.
- b. The computer room, if it is used as an integral part of the emergency response plan.
Unit 1 does not have a plant computer.
C. The shift supervisor's office.
The shift supervisor's (watch engineer's) office is included in the control room area.
- d. The operators' wash room and the kitchen.
The wash room and kitchen are not inside the control room area, but are adjacent to the control room and the Technical Support Center.
The kitchen area will be incorporated into the Technical Support Center HVAC envelope. This will provide a clean, low radiation environment for food storage and preparation. However, the wash room will not be incorporated into either the control room or Technical Support Center HVAC envelope. Our evaluation shows the skin and whole body doses are not significantly increased if time in the wash room is limited to 30 minutes or less per person per shift. Thyroid dose will be kept below the 30 rem limit by use of respirator equipment during the time in the wash room.
- e. The emergency zone should be limited to those spaces requiring operator occupancy. Spaces such as battery rooms, cable spreading rooms, or other spaces not requiring continuous or frequent occupancy after a design basis accident (DBA) generally should be excluded from the emergency zone.
Inclusion of these spaces may increase the probability of smoke or hazardous gases entering the emergency zone. They may also increase the possibility of infiltration into the emergency zone, thus decreasing the effectivehess of the ventilation system in excluding contamination.
It is advantageous to have the emergency zone located on one floor, with the areas included in the zone being contiguous.
-2 The emergency zone and the Technical Support Center are located on the same floor.
- 2. Control Room Personnel Capacity Food, water, and medical supplies should be sufficient to maintain the emergency team (at least five (5) men) for five (5) days.
Food, water and medical supplies for seven control room people for five days will be stored inside the emergency zone (control room and TSC).
- 3. Ventilation System Criteria The following criteria deal with the verification of acceptable system performance and assurance of system availability:
- a. Isolation Dampers - Dampers used to isolate the control zone from adjacent zones or the outside must be leaktight. This may be accomplished by using low leakage dampers or valves. The degree of leaktightness should be doucmented in the SAR.
The existing isolation dampers are not leaktight. The dampers will be replaced with resilient seal low leakage dampers.
- b. Single Failure - A single failure of an active component should not result in loss of the system's functional performance. All the components of the control room emergency filter train will be considered active components.
The active components of the HVAC system do not meet single failure criteria. The HVAC system will be modified or replaced such that all active components meet the single failure criteria. The HVAC duct work is not an active component.
- c. Pressurization Systems - Systems that will pressurize the control room during a radiation emergency should meet the following requirements:
(1) Those systems having pressurization rates of greater than or equal to 0.5 volume changes per hour will require periodic (every 18 months) verification that the makeup is +10% of design value. During plant construction or after any modifications to the control room that might significantly affect its capability to maintain apositive pressure, measurements should be taken to verify that the control room is pressurized to at least 1/8 inch water gauge relative to all surrounding air spaces (while applying the design makeup air rate).
-3 (2) Those systems having pressurization rates of less than 0.5 and equal to or greater than 0.25 volume changes per hour will have identical testing requirements as indicated in (1), above. In addition, at the CP stage, an analysis must be provided (based on the planned leaktight design features) that ensures the feasibility of maintaining 1/8 inch water gauge differential with the design makeup air flow rate.
(3) Those systems having pressurization rates of less than 0.25 volume changes should meet all the requirements for (2), above, except that periodic verification of control room pressurization (every 18 months) will be required.
The HVAC design will employ a zone isolation with filtered recirculated air with a positive pressure. Since the final design of the HVAC is not available, the pressurization rate is not known.
However, the system will be designed and tested to meet the appropriate criteria.
- 4. Toxic Gas Protection Self-contained breathing apparatus for the emergency team (at least 5 men) should be on hand. A six-hour onsite bottled air supply should be available with unlimited offsite replenishment capability from nearby location(s).
Self-contained breathing apparatus with six hour air supply for seven people will be available in the control room. An unlimited supply of air will be available offsite.
- 5. Emergency Standby Filters The installed ESF atmosphere cleanup system is needed to mitigate the consequences of postulated accidents by removing from the atmosphere radioactive material that may be released in the event of an accident.
ETSB will accept ESF atmosphere cleanup systems if the following criteria are met:
- 1. Atmosphere cleanup system should be designed so that they can operate after design basis accidents (DBA) and retain radioactive material after the DBA.
The modified HVAC will meet this criteria.
- 2. The following guidelines are for determining acceptabilityof system design:
- a. Each atmosphere cleanup system should be able to prefilter the air, remove moisture ahead of charcoal adsorbers, and remove particulate matter by HEPA filters before and after the charcoal adsorbers.
-4 When installed, the system will have a pre-filter and HEPA filter ahead of the charcoal filter. Moisture removal is not required in this application. A HEPA filter will be installed after the charcoal filter.
- b. Redundancy of filter systems should be provided, with the trains physically separated so that damage to one system will not cause damage to the other system.
Currently, the filter system is not redundant. Redundant filter systems will be installed with adequate physical separation to preclude damage to both filters from a single source.
- c. All components should be designated as Seismic Category I.
Currently, none of the components are Seismic Category A. The entire control room HVAC system, including duct work, will be upgraded to Category A.
- d. Individual systems should be limited to a volumetric air flow rate of 30,000 cfm.
The HVAC requirements for the control room are approximately 10,000 cfm for the current design. The new design will not exceed 30,000 cfm.
- e. Each system should be instrumented to signal, alarm, and record pressure drop and flow rate at the control room.
HVAC flow rate and filter differential pressure will be recorded in the control room. An annunciator will be provided to alarm on low flow or high differential pressure.
- f. The applicable ESF atmosphere cleanup systems should be automatically activiated after a DBA unless (1) the atmosphere cleanup system is operating during the time the DBA occurs, or (2) the activation is the result of another ESF signal (i.e.,
temperature, pressure).
The emergency mode of operation of the HVAC will be automatically initiated on high radiation at the makeup inlet or containment isolation at 1.0 psig.
- 7. Radiation Shielding Our letters dated September 22, 1977 and October 26, 1977, forwarded information on control room operator doses. This information provides the radiation doses from direct and skyshine radiation. Based on this information, the control room provides adequate shielding for the operators.
-5
- 8. Radioactive and Toxic Gas Hazards
- a. Radiation Hazards The dose guidelines (see General Design Criterion 19, Appendix A of 10 CFR Part 50) used in approving emergency zone radiation protection provisions are as follows:
(1) Whole body gamma:
5 rem (2) Thyroid:
30 rem (3) Beta skin dose:
30 rem The whole body gamma dose consists of contributions from airborne radioactivity inside and outside the control room, as well as direct shine from fission products inside the reactor containment building.
The upgraded control room HVAC and the use of respirators in the operators' wash room will reduce the airborne radioactivity such that these criteria will be met.