ML20055F852

Proposed Tech Specs Reducing Low Condenser Vacuum Scram Setpoint

ML20055F852
Person / Time
Site:	Oyster Creek
Issue date:	07/10/1990
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20055F850	List: ML20055F849 ML20055F851 ML20055F852
References
NUDOCS 9007190293
Download: ML20055F852 (3)

Text

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'oparticul r prot:cti:n in:trument 10 not required; cr th] plcnt to pieced in the-

. protection or safe condition that the instrument initiates. This is accomplished in s* normal manner without subjecting the plant to abnormal operations conditions.- The action and out-of-service requirements apply to all instrumentation within a ,

particular function, e.g., if the requirements on any one"of the ten scram functions  ;

cannot be met tba ,sontrol rods shall be inserted. .

The trip level syatt,.gs not specified in specification 2.3 have been included in this specification. The bases for these settings are discussed below.

The high drywell pressure trip setting is s 3.5 psig. This trip will scram the  !

reactor, initiate reactor isolation, initiate containment spray in conjunction with  ;

low low reactor water level, initiate core spray, initiate primary containment isolation, initiate automatic depressuritation in conjunction with low-low-low-reactor water level, initiate the standby gas treatment ; system and isolate the reactor building. The serem function shuts the core down during the loss-of-coolant accidents A steam leak of about 16 gpm and a liquid leak of about 35 gpm from the primary system will cause drywell pressure to reach the scram point;  ;

j and, therefore, the scram provides protection for breaks greater than the above.

L High drywell pressure provides a second means of initiating the core spray to mitigate the consequences of loss-of-coolant accident. Its trip setting of 53.5 +

peig initiates the core spray in time to provide adequate core cooling. The  ;

i break-sise coverage of high drywell pressure was discussed above. Low-low water level and high drywell pressure in addition to initiating core spray also causes isolation valve closure. These settings are adequate to cause isolation to minimite '

the offsite dose within required limits.

It is permissible to make the drywell pressure instrument channels inoperable during l

performance of the integrated primary containment leakage rate tent provided the l reactor is in the cold shutdown condition. The reason for this is that the j Engineered Safety features, which are effective in case of a LOCA under these i j conditions, will still be effective because they will be activated (when the ,

t Engineered Safety Features system is required as identified in the technical specification of the system) by low-low reactor water level.*

The scram discharge volume has two separate instrument volumes utilized to detect water accumulation. The high water level is based on the design that the water in ,

the SDIV's, as detected by either set of level instruments, shall not be allowed to exceed 29.0 gallons; thereby, permitting 137 control rods to scram. To provide i

further margin, an accumulation of not more than 14.0 gallons of water, as detected by either instrument volume, will result in a rod block and an alarm. The accumulation of not more than 7.0 gallons of water, as detected in either instrument volune will result in an alarm. ,

Detailed analysis of transients have shown that sufficient protection is provided by other scrams below 45% power to permit bypassing of the turbine trip and generator load rejection scrams. However, for operational convenience, 40% of rated power has been chosen as the setpoint below which these trips are bypassed. This setpoint is coincident with bypass valve capacity.

A low condenser vacuum scram trip of 20 inches Hg has been provided to protect the  !

main co'idenser in the event that vacuum is lost. A loss of condenser vacuum would cause the turbine stop valves to close, resulting in a turbine trip

~

oyster Creek 3.1 Amendment No 20, 73, 79, 112

• Correction: 11/30/87 9007190 PDR @OC h,h19 PDC P

,. trcpsicnt. The low c:nd2;cCr vacuu3 trip previd:s o rolitblo b ckup to th3

. turbine trip. Thus, if there is a failure of the turbine trip on low vacuum, the reactor would automatically ecram at 20 inches Hg. The condenser is capable of receiving bypass steam until 7 inches Hg vacuum thereby mitigating the transient and providing a margin.

Main steamline high radiation is an indication of axcessive fuel failure.

Scram and reactor isolation are initiated when high activity is detected in the main steam lines. These actions prevent further release of fission products to the environment. This is accomplished by setting the trip at 10 times normal rated power background. Although these actions are initiated at this level, at lower activities the monitoring system also provides for continuous monitoring of radioactivity in the primary steam lines as discussed in section VII-6 of the FDSAR. Such capability provides the operator with a prompt indication of any release of fission products from the fuel to the reactor coolant above normal rated power background. The gross failure of any single fuel rod could release a sufficient amount of activity to approximately double the background activity at normal rated power. This would be indicative of the onset of fuel f ailures and would alert the operator to the need for appropriate action, as defined by Section 6 of these specifications.

The settings to isolate the isolation condenser in the event of a break in the steam or condensate lines are based on the predicted maximum flows that these systems would experience during operation, thus permitting operation while affording protection in the event of a break.

Thesettingscorregpondtoa flow rate of less than three times the normal flow rate of 3.2X10 lb/hr.

Upon initiation of the alternate shutdown panel, this function is bypassed to prevent spurious isolation due to fire induced circuit faults.

The setting of ten times the stack release limit for isolation of the air-ejector of fgas line is to permit the operator to perform normal, immediate remedial action if the stack limit is exceeded. The time necessary for this action would be extremely short when considering the annual averaging which is allowed under 10CFR 20.106, and, therefore, would produce insignificant effects on doses to the public.

Four radiation monitors are provided which initiate isolation of the reactor i building and operation of the standby gas treatment system. Two monitors are  !

located in the ventilation ducts, one is located in the area of the rufueling '

pool and one is located in the reactor vessel head storage area. The trip logic is basically a 1 out of 4 system. Any upscale trip will cause the desired action. Trip settings of 17 mr/hr in the duct and 100 mr/hr on the refueling floor are based upon initiating standby gas treatment system so as not to exceed allowed dose rates of 10 CFR 20 at the nearest site boundary.

5 The SRM upscale of 5X10 CPS initiates a rod block so that the chamber can be relocatedtoalowerfluxareatomaintainSRMgapabilityaspowerisincreased to the IRM range. Full scale reading is 1 x IC CPS. This rod block is bypassed in IRM Ranges 6 and higher since a level of 5 x 105 CPS is reached and the SRM chamber is at its fully withdrawn position.

The SRM downscale rod block of 100 CPS prevents the instrument chamber from being withdrawn too far from the core during the period that it is required to monitor the neutron flux. This downscale rod block is also bypassed in IRM OYSTER CREEK 3.1-5 Amendment No 2,7,112 01/5/71, 11/5/71 l I

TABLE 3.1.1 PROTECTIVE INSTRU N ATION REQUIREMENTS Reactor Modes Min. No. of Min. No. of in which Function Operable or Instrument Must Be Operable Operating Channels Per

[ tripped] Operable Action Function Trio Settino Shutdown Refuel Startup E!m Trip Systems Tric Systems Beauired*

A. Scraft

1. Manual' Scram X X X X 2 1 Insert control.

rods

2. High Reactor **

Z(s) Z(11) I 2 2 Pressure

3. High Drywell 5 3.5 peig Z(u) Z(u) I 2 2 Pressure

4. Low Reactor ** X X X 2 2 Water Level

-5. a. High water S-29 gal. X(a) X(z). X(z) 2 2 Level in Scram Discharge volume North Side

b. High water 5 29 gal. X(a) Z(z) X(z) 2 2 Level in Scram Discharge volume South Side

6. Low Condenser 2 20 inches hg. X(b) X 2 '2 Vacuum 7.~High Radiation . $ 10 x normal X(s) X X 2 2 in Main Steam background Line Tunnel A

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