ML20209B890
| ML20209B890 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 04/22/1987 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 2NRC-7-089, 2NRC-7-89, GL-85-12, TAC-62924, NUDOCS 8704280535 | |
| Download: ML20209B890 (6) | |
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W 2NRC-7-089 (412)393 7546 Beaver Valley No. 2 Unit Project Organization Telecopy(412)393 7889
"[ Box $8 April 22, 1987 8"
Shippingport. PA 15077 United States Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, DC 20555
SUBJECT:
Beaver Valley Power Station Unit No. 2 Docket No. 50-412 Interim Report on Reactor Coolant Pump Trip Criteria (Generic Letter 85-12) SER Confirmatory item #41
REFERENCES:
1)
NRC letter to DLC, dated Apri1 22, 1986
- 2) DLC letter 2NRC-6-020, dated March 10, 1986
- 3) DLC letter 2NRC-5-146, dated November 15, 1985 4)
DLC letter 2NRC-5-124, dated August 27, 1985 Gentlemen:
The attachment to this letter provides responses to the staff's Interim Report on reactor coolant pump trip criteria (Generic Letter 85-12) transmitted to Duquesne Light Company by reference 1.
This information supplements infor-mation provided earlier by references 2, 3 and 4.
Upon your finding this information sufficient, SER Confirmatory item 41 (c) should be closed.
DUQUESNE LIGHT COMPAhY By J. J. Carey Senior Vice President JJS/ijr Nk/JJS/GL/8512 Attacnment AR/NAR cc:
Mr. P. Tam, Project Manager
- w/ attachment Mr. J. Beall, NRC Sr. Resident inspector
- w/ attachment INPO Records Center
- w/ attachment NRC Document Control Desk
- w/ attachment h
8704280535 870422 0
PDR ADOCK 05000412 3
PDR 1
\\\\
=____
ATTACHMENT BVPS-2 Response to the Interim Report on Reactor Coolant Pump Trip Criteria A.
Detennination of RCP Trip Criteria The staff requests a summary of the selection process which illustrates the rationale leading to the selected trip criterion.
Response
The reactor coolant system / secondary pressure differential has been select-ed to be the RCP trip parameter because, of the three potential parameters, it is the only one which can adequately discriminate between small break LOCA events and other events such as SGTR, steamline and feedline breaks.
The reactor coolant system / secondary pressure differential trip setpoint calculated for BVPS-2, including instrument uncertainties, is 145 psi.
The WOG BVPS-2 analysis results for pressure differential are 278 psi, 790 psi and 822 psi for SGTR, steamline and feedline breaks, respectively.
Accord-ingly, RCP trip will not be predicted to occur for these events.
The BVPS-2 reactor coolant system pressure and reactor coolant system sub-cooling temperature trip setpoints are 1244 psig and 37.5*F, with instru-l ment uncertainties included. The WOG BVPS-2 analysis results give SGTR and non-LOCA lower limits of 1132 psig RCS pressure and 30*F RCS subcooling.
Since the calculated setpoints are greater than the minimum predicted plant conditions, these parameters would not provide adequate RCP trip discrimi-nation capability and were not selected for this reason.
The additional fundamental condition that at least one high-head Safety Injection (HHSI) pump be operational prior to tripping the RCPs is based on the requirements set-forth in the Westinghouse Emergency Response Guide-lines (ERGS), Revision 1, September 1983.
A short description for the reasoning behind this strategy can be found in the ERG Executive Volume under the Generic Issues section dealing with RCP trip / restart.
A brief sumnary of this section is as follows:
Analysis has shown that if the SI system is not in operation, the RCPs i
can be operated to provide core heat removal.
As discussed in WCAP-9753 (Inadequate Core Cooling Studies of Scenarios with Feed"ater Avail-able, Westinghouse Electric Corporation, June 1979) for SBLOCAs with the HHSI pumps not in operation, continued RCP operation provides core heat removal via the break and steam generators.
With the RCPs running, the j
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RCS can be safety depressurized to the point where the accanulators and the low-head safety injection (LHSI) pumps can ensure core heat renoval i
before symptoms of Inadequate Core Cooling (ICC) are exhioited.
Continued RCP operation is also contingent on the availability of appropri-ate minimum RCP support conditions as discussed in the section B1 response.
l It should be noted that continued RCP operation without minimum support conditions is supported only ur. der ICC conditions.
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A1. Instrumentation Identification and Qualification The quality level of the instrumentation used to determine RCP trip set point is requested.
In addition, information on the redundancy of instru-mentation which indicates that RCP or a high head 51 pump is running is requested.
Response
The two reactor coolant system pressure indicators and three steamline pressure indicators for each steam generator are all safety grade quality.
1 Besides breaker position indication for each of the RCPs and high head S1 i
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punps, there are motor anmeter and flow indicators in the control room which provide additional means of deter mining if the pumps are running.
4 A2. Instrumentation Uncertainties for Both Normal and Adverse Containment Concitions 1
The staff questions and corresponoing responses are as follows:
Question i
Can accidents outside containment reasonably create an adverse environment 1
which affects the referenced instruments?
f
Response
The RCS pr essure instruments employed for RCP trip are environmentally i
qualified for design pipe breaks.
4 The main steam pressure transmitters employed for RCP trip are located in 1
evaluated for an arbitrary, non-mechanistic 1.0 f tgtrument cable have been the MSVH area.
The transmitters and associated in i
break in the mainsteam i
line and have been verified to be capable of performing reactor trip and steamline isolation safety functions. Continued exposure to the postulated superheat environment would result in unreliable signals / indication from j
this instrumentation.
However, f ailure of the cable has no adverse effect on reactor trip or steanline isolation signal generation as the cables t
perform these functions prior to exceeding their qualified temperature.
1 For tha purpose of monitoring heat removal during plant cooldown folIowing this specific event, alternative class 1E-powered instrumentation is avail-able in the form of steam generator level, auxiliary feedwater flow, and RCS temperature. The transmitters and associated cable are fully qualified for all other postulated accidents outside containment.
Note, however, th at high energy pipe breaks are not postulated in the MSVH area as it is designated a break exclusion zone in accordance with BTP-MEB 3-1.
1
,i Question What is the influence of an adverse containment on the line connecting between the RCS and the wide range pressure transmitter?
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Response
l The line connecting between the RCS and the wide range pressure transmitter is safety grade quality and is therefore qualified for environments result-ing from design pipe breaks.
Questions Did Stone and Webster verification exclude all interactions, or did it conclude that only one channel of information would be affected, with the remainder of the information available.
Response
it was verified that all the RCS pressure and steamline pressure indicators and sensing lines enployed for RCP trip are protected from the affects of fluid jets and pipe whip for all LOCA and secondary side line breaks.
B.
Potential Reactor Coolant Problems Bl. Assurance that Containment isolation will not cause Problems if it occurs for hon-LOCA Transients and Accioents l
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Demonstrate that, if water services needed for RCP operations are terminat-ed, they can be restored fast enough once a non-LOCA situation is confirmed to prevent seal danage or failure.
Confirm that containment isolation with continued pump operation will not lead to seal or pump damage or failure.
Responses The water services needed for RCP operation include a) the reactor compo-nent cooling water systen (CCP) which supplies cooling water for the RCP ther mal barrier heat exchangers and for the RCP motor bearings oil heat exchangers and b) the RCP seal injection flow which is provided by the chargirg/HHS1 pumps.
The design and operation of the RCP seal injection flow is such that it remains in service under anticipated plant transients. Neither containment isolation phase A or B (CIA or CIB) will isolate RCP seal injection flow.
The seal injecton flow by itself is adequate for providing RCP seal cooling I
which prevents seal damage or failure.
Therefore, RCP seal danage or f ail-ure is precluded due to the continued supply of seal injection water.
The CCP flow is maintained during a CIA signal which therefore permits continued RCP operation.
in the event a CIB occurs, CCP flow to the RCP's is terminated which will require manually stopping the RCPs within approxi-mately five minutes. CCP flow is necessary for RCP motor bearings oil heat i
exchanger s, however, limited operation is possible without pump danage or failure occuring.
CCP flow cannot be restored fast enough following a CIB signal to maintain the RCP's running.
The new symptom-based Emergency Oper ating Procedures (EOPs) provide restart instructions in the event RCP operation is desired. This is consistent with the ERG background documents and the general philosophy that RCPs should be operating to aid in plant cooldown and "S pressure control for non-LOCA transients and accidents.
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Additional information on containment isolation is provided in FSAR Section 6.2.4.
Table 6.2-60 identifies the various containment isolation arrange-ments and states what isolation signals exist for these water systems il supporting RCP operation.
The following provides assurance that upon receipt of a CIB signal, the operator will take the appropriate action.
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- 1. Inrough training, the oper ators are instr ucted that if CCP water flow to the RCPs is isolated on a containment pressure signal, all the RCPs should be stopped within 5 minutes because of loss of RCP motor bearing oil cooling.
- 2. In the new synptom-based E0Ps, one of the operator immediate action steps in E-0, " Reactor Trip or Safety injection", instructs the operator l
to stop all RCPs upon verification that CIB is required.
A subsequent E-0 step instructs the operator to stop all RCPs if there is no CCP flow to the RCPs.
- 3. The operator would be alerted to the RCP conditions and the need to trip the RCPs since one or several monitors would alarm in the control room.
These alarms are synptomatic of the loss of CCP water flow and include the following:
i RCP Alarms Related to CCP Flow Loss:
1.
RCP Lower Beet ing Lube Oil Cooling Water Flow Low 2.
RCP Stator Winding Cooling Water Flow Low l
3.
RCP Upper Bearing Lube Oil Cooling Water Flow Low 4.
RCP Lower Redial Bearing Temperature High 5.
RCP Cooling hater Discharge Temperature High b.
RCP Thermal Barrier Cooling Water Distnarge Temperature High Alarms Related to tr.e CCP System f
1.
CCP Water Sut ge Tank Level High-Low J
l 2.
l 3.
CCP Pump Auto Star t-Stop 4.
High Temperature Alarms on Numerous Components Computer Point input
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1.
RCP Upper Bearing Lube Oil Cooling Water Discharge Temperature I
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2.
RCP Lower Bearing Lube Oil Cooling Water Discharge Temperature 3.
RCP Stator Cooling Water Discharge Temperature i
4 CCP Water Heat Exchanger Header Discharge Line Flow Low it is noted that, if RCP operation (at least one pump) becomes desirable, j
the EOPs provide for RCP restart under the appropriate conditions.
- Also, there ar e function restoration procedur es if a special RCP restart (i.e.,
i without RCP support conditions required) is considered necessar y, f
- 82. Components Required to Trip the RCPs Addr ess whether the components required to trip the RCPs, including ielays power supplies and breakers could be influenced by conditions ' associated with the accidents in question.
What is the estimated time to trip the RCPs manually from the breaker if a trip from the main control board is i
l unsuccessful.
j
Response
i j
The component locations are identified in reference 3 and none of the j
required components are in locations that would be expected to be influ-
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enced by conditions associated with the accidents in question, it is anti-j cipated that if a trip ft om the main control board is unsuccessful it would j
take the operator about 2 minutes to walk from the control room to the j
switchgear area of the service building and trip the breakers.
C.
Oper ator Training and Procedures (RCP Trip)
C1. Description of the Operator Training Program for RCP Trip i
is the background mater ial presented in the response to item Cl provided to the operator s during training?
l
Response
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The same background material regarding the need to trip the RCPs versus the I
desire to keep them running and associated trip criteria are covered in operator training.
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