ML20052F545
| ML20052F545 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 05/07/1982 |
| From: | Withers B PORTLAND GENERAL ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM TAC-44412, NUDOCS 8205130174 | |
| Download: ML20052F545 (6) | |
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May 7, 1982 Trojan Nuclear Plant Docket 50-344 License NPF-1 Director of Nuclear Reactor Regulation ATTN:
Mr. Robert A. Clark, Chief Operating Reactors Branch No. 3 Division of Licensing U. S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Clark:
TROJAN NUCLEAR PLANT NUREG-0737, Item II.B.1 Additioaal Information on Reactor Vessel Head Vent Your letter of February 24, 1982 requested additional information regard-l ing NUREG-0737, Item II.B.1, Reactor Coolant System Vent. The following i
is our response to the subject letter:
NRC Question 1:
Verify that the Reactor Vessel Head Vent System (RVHVS) flow restriction orifices are smaller than the size corresponding to the definition of the loss-of-coolant accident (10 CFR 50, I
Appendix A) by providing pertinent design parameters of the reactor coolant makeup system and a calculation of the maxi-mum rate of loss of reactor coolant through the RVHVS flow restriction orifices (Reference NUREG-0737, Item II.B.1 Clarification A.(4)).
PCE Response The orifices on the vent system are 3/8 in. I.D.
The mass flow through a 3/8 in break is approximately 17.5 lb/see which is within the capacity of the normal makeup water system as discussed in i
Trojan FSAR Section 15.3.1.
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Portland General Bectric CQi,2:wiy Mr. Robert A. Clark i
May 7, 1982 Page two NRC Question 2:
I Describe the materials of construction of. the portions of the RVHVS that forms a part of the reactor coolant pressure boundary, up to
'and including the second normally closed valve, and verify that they l
are compatible with the reactor coolant chemistry and will be fabri-cated and tested in accordance with SRP Section 5.2.3, " Reactor Coolant Pressure Boundary Materials".
PCE Response i
The material for piping and valve in contact with the reactor coolant water is austenitic stainless steel, SS-304 and SS-316 respectively.
The material in contact with _ the reactor coolant is compatible with Trojan's reactor coolant chemistry specified in FSAR _Section 5.2.3.2 and is fabricated in accordance with SRP Section 5.2.3.
NRC Question 3:
i Verify that the block valve for the pressurizer power-operated relief valve is provided with positive valve ' position indication in the Control Room (Reference NUREG-0737, Item II.B.1 Clarifi-cation A.(5)).
j_
PGE Response i
The block valves (M08000A & B) for the pressurizer PORVs are equip-ped with limit switches which provide a positive valve position t
indication (open or closed) in the Control Room. Trojan Technical Specifications (Appendix A to the Facility Operating License),
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Section 3.3.3.9 provides the Limiting Condition for Operation and t
j the Surveillance Requirement for the block valve position indicators to ensure their operability.
NRC Question 4:
Verify that the following RVHVS failures have been analyzed and found not to prevent the essential operation of safety-related systems required for safe reactor shutdown or mitigation of con-sequences of a design basis accident:
a.
Seismic failure of RVHVS components that are not designed to withstand the safe shutdown earthquake.
I l.
Pcedarid Gerieral MW Mr. Robert A. Clark May 7, 1982 Page three b.
Postulated missiles generated by failure of RVHVS components.
c.
Fluid sprays from RVHVS component failures. Sprays from nor-mally unpressurized portions of the RVHVS that are Seismic Category I in Safety Class 1, 2, or 3 and have instrumentation for detection of leakage from upstream isolation valves need not be considered.
PGE Response a.
All components for the Reactor Vessel Head Vent System are designed to be Seismic Category I.
Thus, the analysis for the non-seismic components is not necessary.
- b. & c.
The RVHVS is designed and analyzed in accordance with Regulatory Guide 1.46 " Protection Against Pipe Whip Inside Containment". Regulatory Guide 1.46 excludes breaks for pipe diameter 1 in. or less. Therefore, jet impingement, pipe whip or missile analysis is not required.
NRC Question 5:
Verify that operability testing of the RVHVS and pressurizer vent 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.l.1. A.(11)].
PGE Response The pressurizer PORVs are already included in the Trojan Inservice Inspection Program for operability testing. The Trojan Inservice Inspection Program will be modified to include the RVHVS components for testing in accordance with subsection IWV of Section XI of the ASME Code for Category B Valves.
NRC Question 6:
Submit operating guidelines for use of the RVHVS and pressurizer vent system including the following:
a.
Guidelines to determine when the operators should and should not manually initiate venting, and information and instrumentation
Pbetlanci General Bectric CorTuxuly Mr. Robert A. Clark May 7, 1982 Page four 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 (eg, pressures and temperstures). 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 Con-tainment integrity due to elevated hydrogen levels.
b.
Methods for determining the size and location of a noncondensible gas bubble [ Reference Position (2) and Clarification A.(2)].
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)].
d.
Required operator action in the event of inadvertent opening, or failure to close af ter opening, of the vents including a description of the provisions and instrumentation neces-sary to detect and correct these fault conditions [ Reference Position (2) Clarification A.(2)].
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 hcat can be effectively removed from the reactor coolant system [ Reference Clarifdcation C.(2)].
PGE Response Generic Emergency Response Guidelines developed by the a.-c.
Westinghouse owner's group was submitted to the NRC for l
evaluation. The Function Restoration Guideline FR-1.3,
" Response to Void in Reactor Vessel", provides instructions i
on use of the RVHVS. PGE will utilize this generic guide-line in developing a plant specific procedure for Trojan.
d.
The RVHVS has been designed to prevent inadvertent valve l
opening or failure of a vent to close from generating a leak-l age path. The RVHVS consists of two parallel flow paths with redundant isolation valves in each flow path. Each valve in the flow path is powered from a separate train of power supply.
l Thus, the design features of the RVHVS provide sufficient protec-tion against inadvertent opening of the vent path. The isolation l
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Portland General ElechicCmway Mr. Robert A. Clark May 7, 1982 Page five valves are provided with a positive valve position indication in the Control Room, and should both isolation valves in one vent path inadvertently be in opened position, it will be handled in accordance with the LOCA emergency procedure.
e.
Function Restoration Guideline FR-C.1, " Response to Inadequate Core Cooling" provides instructions to ensure that sufficient coolant flow through steam generators is maintained in lieu of venting.
NRC Question 7:
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 a Human Factors Analysis required by NUREC-0737, Item I.B.1, " Control Room Design Review".
PGE Response Reactor Vessel Head Vent System displays and controls will be con-sidered in Trojan's Control Room Design Review.
NRC Question 8:
It is the NRC position that physical removal of power supply from the RVHVS valves and key lock hand switches, as outlined in i
your April 15, 1980 submittal (Page 22), are acceptable measures to prevent inadvertent RVHVS actuation (Reference NUREG-0737, Item II.B.1 Clarification A.7).
However, your letter of July 17, 1981 states that power lockout to any valve is not considered j
necessary (Page 2).
Verify that the power supply will be removed from the RVHVS valves during normal operation, or the valves are key-locked closed, or describe other design features or adminis-trative measures which will be employed to prevent inadvertent actuation of the RVHVS.
PCE Response NUREG-0737, Item II.B.1 Clarification A.7 states that, "Suffi-cient redundancy should be incorporated into the design to mini-mize the probability of an inadvertent actuation of the subsystem.
Administrative procedures may be a viable option to meet the single-failure criterion".
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l Portland General ElectricCompany Mr. Robert A. Clark May 7, 1982 Page six The Trojan RVHVS has two normally deenergized valves in series in each flow path, which eliminates the possibility of a spuri-ously opened flow path due to spurious movement of one valve.
The failure on any one valve or power supply will not inadvertently open a vent path. Therefore sufficient redundancy is incorported in the RVHVS design to minimize an inadvertent actuation. Further-more, switch handles for the RVHVS isolation valves are T-shaped handles to distinguish them f rom L-shaped handles which are common for most valves. A sign requiring shift supervisor's approval before actuation will also be placed on the switch handles to prevent inadvertent operation of the valves. Based on these fea-tures, we believe that removal of power suppy from the RVHVS valves and key-lock hand switches are unnecessary and could cause an adverse situation if the RVHVS operation is required during emergency.
Sincerely, Bart D. Withers Vice President Nuclear c:
Mr. Lynn Frank, Director State of Oregon Department of Energy
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