ML20091K873
| ML20091K873 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 01/20/1992 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NSD920058, TAC-M81856, NUDOCS 9201270124 | |
| Download: ML20091K873 (4) | |
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' January 20, 1992 U.S. Nuclear Regulatory Corersission Attention: Document Control Desk Washington, D.C.
20555 Centlement Subj ect:
' Response to NRC Request for Additional Information Regarding Proposed Change No. 93 to Technical Specifications Clarification of System / Subsystem Terres (TAC M81856)
Cooper Nuclear Station NRC Docket No. 50 298, DPR 46
' Referencest 1.
_Lettar-from R. B. Bevan to C. R. Ilorn dated Decesaber_ 27, 1991, " Request for Additional Information, cooper Nuclear Station (M818$6)"
2.
Letter frem C. R. Horn to NRC dated September 30, 1991
" Proposed Changu No. 93 to Technical Specifications,
- Clarification of' System / Subsystem Terms" The Nebraska Public Power District-(District) hereby provides its response to:
the NRC Staff Request For_Adaitional Inforraation (RAI) dated December 27, 1991 (Reference 1) concerning the District's. Proposed Shange No. 93. " Clarification of Systein/ Subsystem Terms" (Reference 2)'.
The RAI requested the District to provide further-information to support the proposed change to Section 3.10.F of the Cooper Nuclear Station (CNS) Technical Specifications,-which specifies the.minimun-combination'of' operable low pressure core cooling' systems required during refueling operations,. The District's responses to the NRC Staff's zquest ons are provided below.
i It1should be noted that the District's primary intent in changing Section 3.10.F of the CNS Technical Specifications was to provide clarification of the frequirements_ contained therein to assist operators in its interpretation.
In
- effecting t' to change, the District proposed an additional, conservative requireme require that'during refueling operations, the minimum
.complemer cressure core cooling systems always include at least ono Low Press vuv. nt Injection (LPCI) subsystem. With this preface, the t
- District's response to the NRC Staff's questions is provided below,.
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' January 20, 1992 DHESTION Why isn't at least one of the LPCS (Low Pressure Core Spray) subsystems required to be operable during refueling when fuel is
[in) the core?
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RESPONSE
During refueling, with fuel in the core, requirements for the low pressure emergency core cooling systems consist of provid8.ng standby cooling capability in the event a loss of coolant inventory is experienced.
Since during refueling operations the system la not pressurized, pipe breaks are not postulated to occur; therefore, this standby makeup capability is provided as protection should an inadvertent draining of the-coolant.in the vessel and refueling cavity occur.
In providing backup capability for meeting this requirement, there are no unique requirements attached to the Core Spray System, Should events occur during the refueling mode which inadvertently j
initiate draining of the reactor vessel and refueling cavity, need only exists to flood the reactor core.
If required, one subsystem of either the Core Spray or the Low Pressure Coolant injection (LPCI) Sydtem is alone capabic of providing adequate core flooding under these conditions. These low pressure core cooling systems serve as a backup.to the condensate transfer system, normally used to fin J the refueling cavity.
Therefore, by ensuring that at
-least two of the four low pressure core cooling subsystems are operable to provide core flooding under these circumstances, a single failure proof backup means exists to reflood the core, and accordingly, no special requirements are attached to the Core Spray System..
QUESTION Why is one of the LPCI subsystems required to be operabic during refueling when fuel is in the core?
, EKEfpJiHE In Proposed Technical _ Specification Change No. 93, the District proposed that Section 3.10.F. be changed to specify that while-fuel is in the core, refueling operations may continuo provided.
i one Core Spray subsystem and one LPCI subsystem is available, or two LPCI subsys'tems are-available, In proposing this change, it is the District's intent to ensure..through the Technical Specifications, that during refueling operations, at least one Shutdown Cooling subsystem is available, while ensuring that at least two of four low pressure cooling subsystems are available h
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'J anua ry 20, 1992 for core cooling in the unlikely event that inadvertent vessel draining were to occur.
At CNS, the Residual lleat Removal (RllR) System provides a number of functions.
It consists of two subsystems, e.ich containing two high flowrate pumps with independent suction off the torus, and each also capabic of taking suction from the condensate storage tanks.
This sy.= tem is capabic of operating in a number 01 different modes, which include, but are not limited to the LPCI mode and the Shutdown Cooling rnode.
Ilowever, for the purpose of clarity and compliance, the LPCI mode of kilR system operation is considered a discreet " system," comprised of two, distinct subsystems.
Each LPCI subsystem contains two LPCI (PJIR) pumps,
nortnally aligned to and capable of taking independent suction f rom the torus, and also capable of taking suction from the condensate storage tanks.
During LPCI operation, auction is taken from the torus, routed through and around the RHR llcat Exchangers, and discharged through the LPCI injection valve into the recirculatton discharge pipin6+
During Shutdown Cooling operation, suction is taken from the suction leg of recirculation loop "A," through the Shutdown Cooling isolation valves, and discharged through one or both 10lR llent Exchangers, and returned to the recirculation discharge line via the LPCI injection valvo.
Therefore, with the exception of initiation and control logic and subsystem suction, the Shutdown Cooling mode of the RHR System in essentially congruent to the LPCI system. Therefore, it was the District's intent that, in the absence of any Shutdown Cooling Technical Specification =,
requiring in Section 3.10 F that at least one LPCI subsystem of the low pressure core cooling systems be availabic would ensure that at least one Shutdown Cooling subsyncem was also available during refueling operations.
Q1]EEHQH What is the safety significance of requiring the LPCI subsystem to be operable but not the LPCS subsystem?
EESEqNSE There is no great safety significance in requiring the LPCI subsystem to be operable, while not requiring the Core Spray System to be operable. Au discussed ataove, the intent of requiring at least one LPCI subsystem to be operaole in Section 3.10.P was to ensure that during refueling operations with fuel in the core, at least one Shutdown Cooling subsystem be operable, as the Shutdown Cooling and LPCI systems share many integral components.
In this manner, the District believed this proposed i
U. S. Nuclear Regulatory Commission.
rage 4 of 4 January 20, 1992
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chango was proactive and conservative in the absence of more structured Shutdown Cooling Technical Specifications. Also as discussed above, any one of the four core cooling subsysterns can provide adequate makeup capability during the refueling inode if called upon to do so.
Therefore, there is no special safety significance attached to the Core Spray Systeia during the refueling mode of operation.
Should you have any questions or require any additional infortnation, please contact me, i
Sincerely, ff b flu %U G. R. llorn Nucinar Power Group Manager GRil/ajb j
Attachment 1
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NRC Regional Office Region IV I
NRC Resident Inspector-Cooper Nuclear Station l
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