ML20155D809
| ML20155D809 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/29/1998 |
| From: | COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20155D806 | List: |
| References | |
| NUDOCS 9811040034 | |
| Download: ML20155D809 (4) | |
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,t" ATTACHMENT A TECHNICAL SPECIFICATION BASES (Page 1 of 4)
B3/4.2.D B3/4.5.D -
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INSTRUMENTATION B 3/4.2 BASES 3/4.2'.B
'Emeroenev Core Coolino System Actuation instrumentation The emergency core cooling system (ECCS) instrumentation generates signals to automat actuate those safety systems which provide adequate core cooling in the event of a design basis transient or accident. The instrumentation which actuates the ECCS is generally arranged in a one out of two taken twice logic circuit. The logic circuit is composed of four CHANNEL (s) and each CHANNEL contains the logic from the functional unit sensor up to and including all relays which actuate upon a signal from that sensor. For core spray and low pressure coolant injection, the divisionally powered actuation logic is duplicated and the redundant components are powered from the other division's power supply. The single failure criterion is met through provisions for redundant core cooling functions, e.g., sprays and automatic blowdown and high pressure coolant injection. Although the instruments are listed by system, in some cases the same instrument is used to send the actuation signal to more than one system at the same time.
For effective emergency core cooling during small pipe breaks, the high pressure coolant injection (HPCI) system must function since reactor pressure does not decrease rapidly enough to allow either core spray or the low pressure coolant injection (LPCI) system to operate in time. The automatic pressure relief function is provided as a backup to HPCI, in the event HPCI does not operate. The arrangement of the tripping contacts is such as to provide this function when necessary and minimize spurious operation. The trip settings given in the specification are i
adequate to assure the above criteria are met. The specification preserves the effectiveness of the system during periods of maintenance, testing or calibration and also minimizes the risk of inadvertent operation, i.e., only one instrument CHANNEL out of service.
3/4.2.C ATWS RPT Instrumentation The anticipated transient without scram (ATWS) recirculation pump trip (RPT) provides a means of limiting the consequences of the unlikely occurrence of a failure to scram concurrent with the associated anticipated transient. The response of this plant to this postulated event falls within the bounds of study events in General Electric Company Topical Report NEDO 10349, dated March 1971 and NEDO24222, dated December 1979. Tripping the recirculation pumps adds negative reactivity by increasing steam voiding in the core area as core flow decreases.
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3/4.2.D Reactor Core isolation Coolino Actuation Instrumentation The reactor core isolation cooling system [
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1 QUAD CITIES UNITS 1 & 2 B 3/4.2 2 Amendment Nos.177 8175
J' ATTACilMENT A TECIINICAL SPECIFICATION BASES (Page 3 of 4)
B3/4.2.D B3/4.5.D INSERT "A" Revised Statement:
...provides makeup water to the core in the event of a postulated isolation of the reactor from the main condenser with a loss of feedwater. The system automatically initiates upon receipt of a reactor vessel low-low water level signal utilizing level indicating i
switches in a one-out-of-two taken twice logic scheme.
The system may also be manually started l
J EMERGENCY CORE COOLING SYSTEM B 3/4.5 i
__ BASES i
glfiQ Suoeression Chamber The suppression chamberis required to be OPERABLE as part of the ECC8 to ensure that a sufficient supply of water is available to the HPCI and C8 systems and the LPCI subsystem in th event of a LOCA. This Rmit on suppression chamber minimum water volume ensures that sumden water is available to permit redrculatim cooling flow to the core. The OPERABluTY of the suppression chamberin OPERATIONAL MODE (s) 1,2 or 3 is also required by 8pedftcation 3.7.K.
Repair work might require making the suppression chamber inoperabis. This specification wul permit those repairs to be made and concurrently provide assurance that the irrodisted fuel has a adequate cooling water supply when the suppression chamber must be made Inoperable, draining, in OPERATIONAL MODE (s) 4 or 5.
in OPERATIONAL MODE (s) 4 and 5 the suppression chamber minimum required water volume i reduced because the reador coolant is maintained at or below 212T. Since pressure suppressio is not required below 212T, the minimum water volume is based on not positive suction head (NPSH), recircuistion volume and vortex prevention plus a safety margin for conservatism. With 4
the suppression chamber waterlevelless than the required limit, a5 ECC8 subsystems are inoperable unless they are sligned to an OPERABLE condensate storage tank. When the suppression chamber level is less than 7 feet, the CS system or the LPCI subsystem is considered OPERABLE only if it can take suction from the condensate storege tank, and the condensate storage tank water level is sufficient to provide the required NP8H for the C8 or LPCI pumps.
Therefore, a verification that either the suppression chamber water level is greater than or equ 7 feet of that CS or LPCIis a5gned to take suction from the condensate storage tank and the condensate storage tank contains greater than or equal to 140,000 gallons of make up water, available to the reactor pressure vessel.
3/4.5.D Reactor core Isolation ch The Reactor Core isolation Cooling (RCIC) system is provided to && continuous m@Mwa lo the tsactor core wnen theOOyter systerp'ipisgittati y?i/ind tpW e6d#/.Mhaf",%_tef MtdirAvnst aP"e wer these cer,Edons, me pumping capadty of the RCIC system is sufficient to maintain the water level above the core without any other water system in operation. If the water level in the reactor vessel decreases to the RCIC initiation level, the system automa i
starts. The system may also be manually initiated at any time. The RCIC system is conservative required to be OPERABLE whenever reactor pressure exceeds 150 psig even though the LPCI l
mode of the residual heat removal (RHR) system provides adequate core cooling up to 350 psig I
The RCIC system specifications are applicable during OPERATIONAL MODE (s) 1,2 and 3 when reactor vessel pressure exceeds 150 psig because RCIC is the primary non-ECC8 source of core cooling when the reactor is pressurized.
Fege.3ec is t $olaYed frem de In A W cond eM sc r 6 4 0 *.
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Ioss of t'ea.ctor QUAD CITl5S - UNITS 1 & 2
~fe ed u a.d e rt.f B 3/4.5-3 issued by letter I
dated June 17,1998 1
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