ML13317A133
| ML13317A133 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/01/1982 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TAC-44128, TASK-2.B.1, TASK-TM NUDOCS 8206030179 | |
| Download: ML13317A133 (6) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING, June 1, 1982 (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 NUREG-0737, Item II.B.1 - Reactor Coolant System Vents Response to Request for Additional Information San Onofre Nuclear Generating Station Unit 1
References:
- 1. Letter, D. M. Crutchfield, NRC, to R. Dietch, SCE, Reactor Coolant System Vents, Request for Additional Information, March 16, 1982
- 2. Letter, K. P. Baskin, SCE, to D. M. Crutchfield, NRC, Post-TMI Requirements, NUREG-0737, April 1, 1982
- 3. Letter, K. P. Baskin, SCE, to D. M. Crutchfield, NRC, NUREG-0737, Item II.B.1 - Reactor Coolant System Vents, April 30, 1982 Reference 1 provided us with a request for additional information concerning the design, surveillance, and operation of the reactor coolant gas vent system at San Onofre Unit 1. Reference 2 provided you with the information (i.e., system description and engineering drawings) necessary to perform an independent design review of the subject system. Reference 3 provided you with the system operating instructions and indicated that the Westinghouse Owner's Group is preparing guidelines which should establish the plant conditions that would necessitate primary coolant system venting.
The purpose of this correspondence is to respond to those items in Reference 1 that have not been previously addressed in References 2 and 3.
Accordingly, the following responses are provided:
Item:
- 1. The following items apply to the portions of the RCSV system that form a part of the reactor coolant pressure boundary, up to and including the second normally closed valve (reference NUREG-0737, Item II.B.1 Clarification A.(7)):
8206030179 820601 PDR ADOCK 05000206 P.. 13
Mr. D.
June 1, 1982
- a.
Provide the design temperature and pressure of the piping, valves and components.
Response
The design pressure and temperature of the Reactor Coolant Vent System (RCVS) piping, manual valves and components, up to and including the second normally closed valve that form a part of the reactor coolant pressure boundary, are 2500 psig and 650oF respectively.
The solenoid valves have a design pressure and temperature of 2485 psig and 650 0F.
- b.
Verify that the piping, valves, components, and supports are classified Seismic Category 1 and Safety Class 2.
Response
The RCVS piping, valves, components, and supports, up to and including the second normally closed valve that form a part of the reactor coolant pressure boundary, are classified as Seismic Category A and are designated as Safety Related. The RCVS piping, fittings and supports have been seismically analyzed and designed to withstand the consequences of a 0.67g Housner earthquake. The majority of the system piping was designed to ANSI B31.1 (original plant design criteria) and purchased in conformance with the quality assurance requirements of 10 CFR Part 50, Appendix B. Some piping and a few fittings, however, were designed and purchased to ASME Boiler and Pressure Vessel Code (B and PV)Section III, Class 2 because of favorable delivery dates.
The manual valves were designed to ANSI B16.34 and purchased in conformance with the quality assurance requirements of 10 CFR Part 50, Appendix B. The solenoid valves were designed to ASME B and PV Code Section III, Class 2 and designated as Seismic Category I, Active components.
- c.
Describe the instrumentation that has been provided to detect and measure RCSV system isolation valve seat leakage (reference Appendix A to 10 CFR Part 50, General Design Criterion 30).
Response
No-instrumentationnhas been or will be installed that will detect leakage specifically from this reactor coolant-gas vent system.
Existing San Onofre Unit 1 procedures S01-1.2-7, "Reactor Coolant System Leakage" and S01-12.2-7, "RCS Hot Leak Rate Test" provide the necessary actions to detect and respond to primary system leakage in excess of that specified in the Technical Specifications.
- d.
Describe the materials of construction and verify that they are compatible with the reactor coolant chemistry and will be fabricated and tested in accordance with SRP Section 5.2.3, "Reactor Coolant Pressure Boundary Materials."
Mr. D.
June 1, 1982
Response
The materials of construction for the RCVS components, up to and including the second normally closed valve that form a part of the reactor coolant pressure boundary, are as described below:
Piping ASTM A312, Type 316 Fittings ASTM A182, F 316 Flanges ASTM A182, F 316 Manual Valves ASTM A182, F 316 Solenoid Valves ASME SA182, F 316L These materials are compatible with the reactor coolant chemistry and are identical in chemical composition to many other existing components forming the reactor coolant pressure boundary.
The solenoid valve materials of construction were fabricated and tested in accordance with SRP Section 5.2.3, "Reactor Coolant Pressure Boundary Materials."
All other materials of construction were fabricated and tested in accordance with their applicable ASTM material specification (original plant design criteria).
- e.
Demonstrate that internal missiles and the dynamic effects associated with the postulated rupture of piping will not prevent the essential operation of the RCSV system (i.e., at least one vent path remains functional) (reference Appendix A to 10 CFR Part 50, General Design Criterion 4).
Response: The majority of RCVS piping and components are located in missile protected compartments (reactor refueling cavity and pressurizer compartment). A portion of the reactor head vent piping and the solenoid valves that control venting of the reactor head are routed along the outside of the pressurizer shield wall just above Elev.
42'-0" (operating deck). There are no moderate or high energy lines in this area that could cause internal missiles associated with a postulated pipe rupture.
The RCVS is located in areas where a postualted pipe rupture will not prevent the system from performing its designed function of venting the reactor head.
Item: 2. Verify that the following RCSV system failures have been analyzed and found not to prevent the essential operation of safety-related systems required for safe reactor shutdown or mitigation of the consequences of a design basis accident:
- a.
Seismic failure of RCSV system components that are not designed to withstand the safe shutdown earthquake.
Response
All RCVS components have been designed to withstand the safe shutdown earthquake (SSE). Therefore, an RCVS component failure due to the effects of an SSE are not postulated.
- b.
Postulated missiles generated byfailure of RCSV system components.
Mr. D.
June 1, 1982
Response
Postulated missiles generated by failure of RCVS components will be contained in either the reactor refueling cavity, pressurizer compartment or along the outside of the pressurizer shield wall at Elev. 42'-0". There are no safety-related systems, required for safe shutdown of the reactor or mitigation of the consequences of a design basis accident, located in these areas that are within line of sight or trajectory range of postulated missiles.
- c.
Fluid sprays from RCSV system component failures. Sprays from normally unpressurized portions of the RCSV system that are Seismic Category 1 and Safety Class 1, 2 or 3 and have instrumentation for detection of leakage from upstream isolation valves need not be considered.
Response
Flow restricting orifices have been installed in the vent piping in close proximity to the reactor head vent nozzle and pressurizer vent nozzle. These elements prevent high energy mass flow rates through vent piping following a postulated system component failure. Postulated fluid sprays caused by RCVS component failures will not interfere with the essential operation of safety-related systems.
Item: 3. Demonstrate, using engineering drawings (including isometrics) and design descriptions as appropriate, that the RCSV paths to the containment atmosphere, both direct and by way of the pressurizer relief tank rupture disc, discharge into areas:
- a.
That provide good mixing with containment air to prevent the accumulation or pocketing of high concentrations of hydrogen.
Response
(Note:
Use the drawings provided with Reference 2)
The RCVS discharges either into the pressurizer relief tank or directly into the containment atmosphere via a 26" ventilation duct. Under normal operating conditions, venting to the relief tank will contain non-condensible gases within the tank or within the RCS drain tank and radio-active gaseous waste system. Venting to the 26" ventilation duct will assure adequate mixing of hydrogen and air as the mixture is circulated through the containment atmosphere. This circulation will prevent accumulation or pocketing of high concentrations of hydrogen. Operation of the hydrogen recombiners will prevent excessive or hazardous hydrogen concentrations within the containment atmosphere.
When venting the RCS to the pressurizer relief tank, a failure of the relief tank rupture disk will cause a mixture of water, steam and noncondensible gases to fill the pressurizer compartment. If this occurs, venting of the RCS will be diverted directly to the containment atmosphere via the 26". ventilation duct. This duct penetrates the pressurizer compartment and will remove the non-condensible gases that may have accumulated within the space.
Mr. D.
June 1, 1982
- b.
In which any nearby structures, systems, and components essential to safe shutdown of the reactor or mitigation of a design basis accident are capable of withstanding the effects of the anticipated mixtures of steam, liquid, and noncondensible gas discharging from the RCSV system.
Response
There are no structures, systems and components essential to safe shutdown of the reactor or mitigation of a design basis accident, that are close enough to the RCVS to be effected by anticipated mixtures of steam, liquid and noncondensible gases discharged from the system.
Item: 4.
Verify that operability testing of the RCSV system valves will be performed in accordance with subsection IWV of Section XI of the ASME Code for Category B valves (reference NUREG-0737, Item II.B.1 Clarification A.(11)).
Response
The response to NUREG-0737, Item II.B.1 Clarification A.(11),
provided as Enclosure 2 to Reference 2, indicated that provisions have been made for operability testing. We also indicated that surveillance procedures will be developed in accordance with the referenced ASME requirements.
Item:
- 5. Submit operating guidelines for use of the RCSV system including the following:
- a.
Guidelines to determine when the operator should and should not manually initiate venting, and information and instrumentation required for this determination (reference NUREG-0737 Item II.B.1 Clarification A.(2)). The guidelines to determine whether or not to vent should cover a variety of reactor coolant system conditions (e.g., pressures and tempertures). The effect of the containment hydrogen concentration on the decision to vent or to continue venting should also be addressed considering the balance between the need for increased core cooling and decreased containment integrity due to elevated hydrogen levels.
Response
We have responded to this item in Reference 3.
- b.
Methods for determining the size and location of a noncondensible gas bubble (reference Position (2) and Clarification A.(2)).
Response
See response to item 5.a.
- c.
Guidelines for operator use of the vents, including information and instrumentation available to the operator for initiating or terminating vent usage (reference Position (2)).
Mr. D.
June 1, 1982
Response
See response to item 5.a.
- d.
Required opertor actions in the event of inadvertent opening, or failure to close after opening, of the vents including a description of the provisions and instrumentation necessary to detect and correct these fault conditions (reference Position (2) and Clarification A.(2)).
Response
See response to item 5.a.
- e.
Methods which in lieu of venting will assure that sufficient liquid or steam will flow through the steam generator U-tube region so that decay heat can be effectively removed from the reactor coolant system (reference Clarification C.(2)).
Response
See response to item 5.a.
Item: 6. Verify that all displays (including alarms) and controls, added to the control room as a result of the TMI Action Plan requirement for reactor coolant system vents, have been or will be considered in the human factors analysis required by NUREG-0737, Item 1.D.1, "Control-Room Design Review."
Response
To the extent practical, and giving consideration to present control room design, the human factors considerations in the referenced requirement were used. The system controls and annunciators are compatible with the existing control room configuration.
If you have any questions, please let me know.
Very truly yours,