ML20214R911
| ML20214R911 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 09/30/1986 |
| From: | Klapproth J, Sozzi G, Stoll C GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20214R897 | List: |
| References | |
| DRF-A-2423, DRF-A00-2423, MDE-101-0986, MDE-101-986, NUDOCS 8706090052 | |
| Download: ML20214R911 (13) | |
Text
3 MDE-101-0986 DRF A00-2423 September 1986 EVALUATION OF HPCI AND RCIC OPERABILITY REQUIREMENTS AT LOW VESSEL PRESSURE FOR THE PILGRIM NUCLEAR POWER STATION Prepared by:
/
i C.H.Stoll, Principal Engineer Application Engineering Services Reviewed by:
ChOtM J. F.KlapprotR9, Principal Licensing Engineer Licensing Services D
Approved by:
Ai
/ G.L.Sopzi, diager Application Engineering Services GENER AL h ELECTRIC NUCLEAA ENERGY BUSINESS OPERATIONS GENERAL ELECTRIC COMPANY e 175 CURTNER AWNUE e SN4 JOSE, CN.lFC4tNIA 95125 0706090052 070601 PDR ADOCK 05000293 P
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IMPORTANT NOTICE REGARDING CONTENTS OF THIS REPORT 1
Please read carefully The only undertakings of General Electric Company respecting information in this document are contained in the contract be-tween the customer and General Electric Company, as identified in purchase order number 63569 for this report and nothing contained in thic document shall be construed as changing the contract. The use of this information by anyone other than the customer or for any purpose other than that for which it was
- intended, is not authorized; and with respect to any unauthorized use, General Electric Company makes no representation or warranty, and assumes no liability as to the completeness, accuracy, or usefulness of the information contained in this document.
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TABLE OF CONTENTS
- 1. INTRODUCTION..............................................
1
- 2. BACKGROUND................................................
2
- 3. EVALUATION................................................
2 3.1 HPCI SYSTEM DESIGN BASIS 2
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3.2 RCIC SYSTEM DESIGN BASIS..............................
5 3.3 REVIEW OF SAFETY ANALYSES.............................
5 1
3.4 OPERATIONAL CONCERNS 6
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4.,
SUMMARY
AND CONCLUSIONS
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MDE-101-0986 ABSTRACT An evaluation has-been performed to verify the operability re-quirements for the HPCI and RCIC systems for the Pilgrim Nuclear Station.- The conclusion of this evaluation is that the HPCI and RCIC are not required to operate below 150 psig vessel pressure to comply with the licensing basis and safety requirements of the Pilgrim Nuclear Station.
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MDE-101-0986 1.
INTRODUCTION The purpose-of this report is to present the results of an evaluation performed for the Boston Edison (BECo) to verify the required operabiltiy range for the high pressure coolant injec-tion system (HPCI) and the reactor core isolation cooling system (RCIC) at the Pilgrim Nuclear Power Station. The results of this evaluation are intended to support a
change to the technical specifications regarding the pressure range over which these systems are required to operate.
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MDE-101-0986 2.
BACKGROUND Current technical specifications require that the HPCI system provide a minimum flow to the vessel of 4250 gpm between 1000 and 150 psig vessel pressure.
Similarly, the technical specification for the RCIC system re-quire a flow rate of 400 gpm for a range of vessel pressure from 1000 psig to 150 psig.
The technical specifications also state that both the HPCI and the RCIC should remain operable down to a vessel pressure of 104 psig (which corresponds to the vessel pressure at rated flow of the core spray system). The HPCI and RCIC are currently tested at 1000 psig and 150 psig to verify that minimum flow rate require-ments are met. However, verification of operability at 104 psig presents some practical operational difficulty.
3.
EVALUATION The desig.n bases and safety analyses involving the performance of both the HPCT and the RCIC systems for the Pilgrim Nuclear Sta-tion were reviewed to establish the performance requirements of these systems.
3.1 HPCI SYSTEM DESIGN BASIS l
The primary design goal of the HPCI system is to provide core cooling to mitigate the consequences of the more probable "small _
MDE-101-0986 break" size range of postulated-loss of coolant. accidents (LOCAs). The "small break" size range is the range of break sizes for which the reactor vessel will not depressurize rapidly without assistance from the Automatic Depressurization System (ADS).
This range is approximately 0.0.to 0.10 sq ft for postu-lated breaks in the_ recirculation line which is the most limiting break location for core cooling. The ADS, coupled with one of the several low pressure ECCS pumps, serves as a backup to the HPCI for mitigation of "small break" LOCAs coincident with the loss of off-site power.
The ADS is designed to depressurize the~ reactor vessel to 100 psig or lower.- This is substantially below the.
pressure at which both the core spray and LPCI systems are capable of coolant injection to the reactor vessel (1).
The HPCI.also provides some supplemental assistance to the low pressure ECCS' in the' intermediate break size range, although it is not a design basis. For postulated large pipe breaks where the water level changes
- rapidly, the vessel pressure also drops rapidly and the low prc;sure ECCS ate the prime mitigating sys-tems. Since HPCI is a steam turbine powered system utilizing reactor vessel _ steam pressure as the power source, it is not designed for operation below 150 psig and is not relied upon for large break LOCA mitigation.
In addition to the design basis of mitigating the consequences of L
small pipe breaks, the HPCI also incidentally provides a source (1) The vessel pressure at incipient flow to the vessel is in excess of 200 psig for both the core spray and the LPCI systems.
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MDE-101-0986 e
of high pressure inventory makeup to maintain vessel level during potential events resulting in the loss of normal feedwater. This function of HPCI is redundant to the reactor core isolation cooling-system (RCIC) which is the primary source of inventory makeup for events resulting in the loss of the normal heat sink-such.as the loss of feedwater. Further core protection for this type of event is provided by the ADS coupled with the low pres-sure ECCS (core spray and LPCI) which ensures adequate cooling of the core even in the absence of high pressure coolant injection.
It should also be noted that the core spray and LPCI systems are capable of providing substantial flow to the reactor vessel at vessel pressure of 150 psig and
- above, therefore there is a
significant overlap in the operating pressure range of the high pressure and low pressure ECCS pumps even though it is not re-quired (2).
In summary, the primary design basis function of the HPCI system is to provide adequate core cooling to mitigate postulated -small break LOCA events.. A secondary incidental function is o provide a backup source of makeup inventory for events involving loss of
- feedwater.
Neither of these functions require the HPCI to be 1
l operable below 150 psig.
i (2) The ADS is designed to depressurize the reactor vessel to 100 psig or lower for injection from the low pressure ECCS if the vessel does not depressurize by some other means.
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MDE-101-0986 3.2 RCIC SYSTEM DESIGN BASIS The primary design goal of the RCIC system is to provide inven-tory makeup to maintain reactor water level above the core during anticipated transients resulting in the loss of the normal heat sink such as the loss of feedwater. The HPCI system would provide redundancy in the unlikely event that both normal feedwater and the RCIC are lost.
Although the RCIC can also provide inventory makeup during postu-lated small break LOCAs (a backup to the HPCI) no credit is taken for this capability for licensing analysis sinr-thc C1c is not considered a safety system.
In swnmary, the design basis of the RCIC is to provide inventory makeup to maintain vessel level during transients resulting in the loss of the normal heat sink. The RCIC is not designed or required to provide flow to the vessel at pressures below 150 psig.
3.3 REVI'EW OF SAFETY ANALYSES The safety analyses performed to license the operation of the Pilgrim Nuclear Power Station were reviewed to determine the pressure range for which HPCI is assumed to be operable.'None of the analyses take credit for HPCI operation (either directly or indirectly) below 150 psig.
The LOCA safety analyses take credit for core spray flow into the 4
MDE-101-0986 vessel at vessel pressure below 205 psig. However, with the approved GE licensing evaluation models SAFE /REFLOOD and CHASTE no credit for spray cooling heat transfer in the hottest fuel-bundle is taken until the pressure at rated flow for the core spray (104 psig vessel pressure) is reached. The LOCA analyses do l
not take any credit whatsoever for operability of the RCIC, since the RCIC is not considered a safety system. However, analysis of loss of feedwater transients take credit for the capability of the RCIC at high pressures, to prevent the vessel level from dropping below the top of the core. The vessel pressure during a
loss of feedwater remains high (near reactor operating pressure) throughout the transient.
3.4 OPERATIONAL CONCERNS The performance capability of the RCIC or HPCI could also be a
consideration in bringing the plant to cold shutdown during some postulated scenarios. For example, in the event of a
loss of feedwater, the RCIC system would provide the makeup inventory to maintain vessel water level (The HPCI system would provide a
backup capability for the RCIC). In order to bring the plant to cold shutdown, the vessel would eventually have to be depres-surized below 150 psig to initiate the shutdown cooling mode of the 1GH1 system.
The RCIC and the HPCI system steam lines do not isolate until the vessel pressure drops below 100 psig and either of these systems would provide adequate inventory makeup until the RHR shutdown MDE-101-0986 cooling was initiated. However, even if the RCIC and HPCI systems did not function below 150
- psig, the reactor can be safely brought to cold shutdown. The reactor could be depressurized from 150 psig to the operating range of the RHR shutdown cooling system with the bypass to the condenser or with limited use of the SRVs.
Inventory makeup during vessel depressurization below 150 psig may not be required, but if it were, either of the core spray loop pumps or any of the RHR pumps operated in the LPCI mode could be used to provide necessary inventory raakeup.
4.
SUMMARY
AND CONCLUSIONS The design bases of both the HPCI and the RCIC systems for the Pilgrim Nuclear Station include coolant injection to the reactor vessel for vessel pressure between 1100 psig and 150 psig.
The safety analyses for Pilgrim take no. credit for operation of either the HPCI or RCIC systems below 150 psig either directly or indirectly. Furthermore, none of the beneficial features of either HPCI or RCIC rely on operability-below 150 psig.
The Bases section of the Pilgrim technical specifications incor-rectly state that safety analyses take no credit for core spray flow into the vessel above 104 psig, and this statement should be appropriately revised to avoid incorrect inference regarding HPCI or RCIC operability requirements.
Therefore, it is concluded that the operability of the HPCI and the RCIC systems is not required below 150 psig vessel pressure MDE-101-0986 and there is no basis for a technical specification requiring operation below 150 psig.
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REFERENCES 1.
Pilgrim Nuclear Station Technical Specifications sections 3.5.C, 3.5.D, 4.5.C, & 4.5.D
- 2. " Assessment of Operation of The Pilgrim Nuclear Power Station With The HPCI System Out-Of-Service" October 1985 (NEDC-31105).
- 3. " Pilgrim Nuclear Power Station Loss Of Coolant Accident (LOCA)
Analysis Update" September 1984 (NEDO-30767).
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