ML20247B297

Proposed Tech Specs,Changing Requirements for RHR Sys Flow When in Mode 6 (Refueling)

ML20247B297
Person / Time
Site:	Catawba
Issue date:	09/06/1989
From:	DUKE POWER CO.
To:
Shared Package
ML20247B294	List: ML20247B287 ML20247B297
References
NUDOCS 8909120429
Download: ML20247B297 (8)

Text

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Attachment 1 e

Proposed Technical Specification Changes (i.

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.s 8909120429 89C906 PDR ADOCK 05000413 P FDC

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I REFUELING OPERATIONS I

3/4.9.8 RESIOUAL HEAT REMOVAL AND COOLANT CIRCULATION HIGH WATER LEVEL LIMITING CONDITION FOR OPERATION 3.9.8.1 At least one residual heat removal loop sh'all be OPERABLL and in operation.* f i

APPLICABILITY: MODE 6, when the water level above the top of the reactor i

. vessel flange is greater than or equal to 23 feet. l I'

ACTION:

With no residual heat removal loop OPERABLE and in operation, suspend all operations involving an increase in the reactor decay heat load or a reduction in boron concentration' of the Reactor Coolant System and immediately initiate corrective action to return the required residual heat removal loop to OPERABLE and operating status as soon as possible. Close all containment penetrations 8' I .providing direct access from the containment atmosphere to the outside atmos-phe,re within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. ,

SURVEILLANCE REQUIREMENTS

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4.9.8.1 At least once per twelve hours one residual heat removal loop shall be verified in operation and circulating reactor coolant at a flow rates a) greater than or equal to 1000 gpa, and b) sufficient to maintain the RCS temperature at less than or equal to 140 F.

"The residual heat removal loop'may be removed from operation for up to I hour per 8-houe period during the performance of CORE ALTERATIONS in the vicinity of the rea' tor vessel hot legs. .

CATAWBA - UNITS 1 & 2 3/4 9-10

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REFUELING OPERATIONS j LOW WATER LEVEL LIMITING CONDITION FOR OPERATION 3.9.8.2 Two independent residual heat removal loops shall be OPERABLE, and at least one residual beat removal loop shall be in operation.*

APPLICABILITY: MODE C, when the water level above the top of the reactor l vessel flange is less than 23 feet.

ACTION:

a. With less than the required residual heat removal loops OPERABLE, immediately initiate corrective action to return the required resi-dual heat removal loops to OPERABLE status, or establish greater than or equal to 23 feet of water above the reactor vessel flange, as soon as possible.

With no resid'al u heat removal loop in operation, suspend all

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operations involving a reduction in boron concentration of the Reactor Coolant System and immediately initiate corrective action to return the required residual heat removal loop to operation.

Close all containment penetrations providing direct access from the containment atmosphere to the outside atmosphere within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

SURVEILLANCE REQUIREMENTS 1 9.9.2 ^t 'eart cae esidus! heet e eve! !ce; th !' be ver 4 'ied 4a ope-etic' and c4"eu'et4 g *eacto- cecient at a #!ce ate # gr::t:r th:r er 0;u:1 t: -

?OOO ;p= at least cace pee 12 heues .-

4.9.8.2 At least once per twelve hours one residual heat removal loop shall be verified in operation and circulating reactor coolant at a flow rates a) greater than or equal to 1000 gpm, and b) sufficient to maintain the RCS temperature at less than or equal to 14d" F.

" Prior to initial criticality, the residual heat removal loop may be ren 1ved from operation for up to I hour per 8-hour period during the performance of CORE ALTERATIONS in the vicinity of the reactor vessel hot legs.

CATAWBA - UNITS 1 & 2 3/4 9-11

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j REFUELING OPERATIONS n,. .

'd BASES

- 3/4.9.5 Col #4UNICdTIONS The requirement for communications capability ensures that refueling i station personnel can be promptly informed of significant changes in the facility status or core reactivity conditions during CORE ALTERATIONS.

3/4.9.6 MANIPULATOR CRANE l l

The OPERABILITY requirements for the manipulator cranes ensure that:

(1) manipulator cranes will be used for movement of control rods and fuel assemblies, (2) each crane has sufficient load capacity to lift a control rod or fuel assembly, and (3) the core internals and reactor vessal are protected from excessive lifting force in the event they are inadvertently engaged during lifting operations.

3/4.9.7 CRANE TRAVEL - SPENT FUEL STORAGE POOL BUILDING The restriction on movement of loads in excess of the nominal weight of a fuel and control rod assembly and associated handling tool over other fuel assemblies in the storage pool ensures that i.1 the event this load is dropped: i (1) the activity release will be limited to that contained in a single fuel assembly, and (2) any possible distortion of fuel in the storage racks will not result in a critical array. This assumption is consistent with the activity release assumed in the safety analyses.

3/4.9.8 RESIDUAL HEAT REMOVAL AND COOLANT CIRCULATION The requirement that at least one residual heat removal loop be in operation ensures that: (1)' sufficient cooling capacity is available to remove decay heat and maintain the water in the reactor vessel below 140*F as required during the REFUELING MODE, and (2) sufficient coolant circulation is maintained through the core to minimize the effect of a baron dilution incident and prevent boron stratification.

The requirement to have two residual heat removal loops OPERABLE when there is less than 23 feet of water above the reactor vessel flange ensures that a single failure of the operating residual heat removal loop will not result in a complete loss of residual heat removal capability. With the reactor vessel head removed and at least 23 feet of water above the reactor vessel flange, a large heat sink is av~ailable for core cooling. Thus, in the event of a failure of the operating residual heat removal loop, adequate time is provided to initiate emergency procedures to cool the core.

To prevent vortexing in the suction of the residual heat removal pumps, the flow rate requirements for the residual heat removal system were lowered from 3000 gpm to 1000 gps. A specific surveillance has been added to ensure the flow remains high enough to ensure the reactor coolant system temperature remains below 140 F. The problems associated with vortexing and mid-loop operations Ja'provided in Generic Letter 88-17, Loss of Decay Heat Removal.

Gr6 CATAWBA - UNITS 1 & 2 B 3/4 9-2

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-Attachment 2 Discussion, No Significant Hazards Analysis and-Environmental Impact Statement v.

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.-- " DISCUSSION, NO SIGNIFICANT HAZARDS ANALYSXS AND ENVIRONMENTAL' IMPACT STATEMENT The' proposed amendment would:

Change the requirements for Residual' Heat Removal to allow reduced flow

>during times when the Reactor Coolant System is partially drained.

The change would reduce the' specific requirement to maintain Resideal Heat Removal flow from 'at greater than or equal to 3000 gpm' to 'at greater than i or equal to 1000 gpm' as required by specification surveillance 4.9.8.1 and 4.9.8.2.

Also a surveillance to ensure Reactor Coolant System temperature is maintained below 140 F has been added to the~ surveillance requirements.

The bases for specifications 3/4.9.8.1 and 3/4.9.8.2 have been modified'to agree with the proposed Technical Specification changes.

Each unit at Catawba Nuclear Station has two independent Residual Heat Removal (ND) Systems. The normal function of the ND System is to remove heat energy from.

the core'and Reactor Coolant (NC) System during cooldown and refueling operations. The ND System is'also used to transfer refueling water between the Refueling Water Storage Tank and~ refueling cavity at the beginning and end of refueling operations. The ND System is also used as part of the Safety Injection System and Containment Spray System during an accident condition.

Detailed information concerning the ND System may be found in section 5.4.7 of the Catawba FSAR.

As stated in the bases of the Technical Specifications on page B.3/4 9-2, the ND System and the required flow rates for the ND System serve two purposes.

The flow rate ensures sufficient cooling capacity is available to remove decay heat and maintain the water in the reactor vessel below 140 F as required during refueling. The flow rate also ensures sufficient coolant circulation is maintained through the core to minimize the effect of a boron dilution incident and prevent boron stratification.

On October 17, 1988 the NRC issued Generic Letter (GL) 88-17 to licensees. On page 5 of the attachment to the GL, program enhancement (5) Technical Specifications, recommended that licensees identify and submit appropriate changes to Technical Specifications that restrict or limit the safety benefit of actions identified in GL 88-17. On pages 5 and 6 of Enclosure 1 to the GL in section 2.1.2, vortexing is discussed. Vortexing at the junction of the ND System suction line and the NC System will occur if water level is too low, a situation to be avoided since this may~ introduce air into the ND System pump suction. Vortexing can occur more easily when flow is high. As stated in section VII.E. of NUREG-1269 on page 32, reduced ND System flow rate wou13 provide a greater margin against vortexing and preclude an inadvertent loss of decay heat removal capability due to air entrainment and cavitation of the ND System pumps. This amendment will allow lower flow rates and reduce our susceptibility to vortexing.

.The proposed amendment will not change the bases for specifications 3.9.8.1 and 3.9.8.2. A ND flow rate of 1000 gpm is satisfactory to maintain NC System 1

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DISCUSSION, NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT temperature below 140 F, the effect of a boron dilution incident is minimized and boron stratification is prevented. Depending on the status of the NC System (i.e. whether the head is on or off, water level in NC system), the temperature of the system can be monitored using the incore thermocouple, the wide range RTDs or the temperature indication at the inlet and the discharge of the ND System heat exchangers. When the NC system is at its lowest level the

-temperature indication at the inlet and the. discharge of the ND System heat exchangers is used. In other words, the required flow rate for the ND system will be dictated by the status of the core (e.g. refueling completed - low decay heat, recently shut down - high decay heat removal) and the level of water in the NC System. Allowing the flow rates to be reduced will aid in preventing vortexing and air entrainment into the ND and NC Systems. As long as a ND pump is running, even at flow rates as low as 1000 gpm, there is enough mixing in the flow to ensure no boron stratification occurs in the NC System. The ND pumps are also needed to minimize the effect of boron dilution scenario. This is accomplished by mixing the flow to ensure uniform distribution of the boron in the NC System. Nitigation of a boron dilution scenario is performed by a boron injection flow path, a centrifugal charging pump and a borated water source.

These are required operable by specifications 3.1.2.1, 3.1.2.3 and-and 3.1.2.5 during periods of reduced NC System inventory.

This amendment will also make the surveillance requirements for Technical Specifications 4.9.8.1 and 4.9.8.2 the same as the surveillance requirements for Technical Specifications 4.4.1.4.1.2 and 4.4.1.4.2. This would aid in eliminating operator confusion for the operating requirements of the ND System.

Vortexing is not a concern when the water level above the top of the reactor vessel flange is greater than or equal to 23 feet (reference specification 3/4 9.8.1). The surveillance requirement 4.9.8.1 is being modified to be consistent with surveillance requirements 4.9.8.2, 4.4.1.4.1.2 and 4.4.1.4.2.

This proposed amendment to the Technical Specifications has also been reviewed in regard to the analyses being performed to address the concerns raised by Bulletin 88-04, Potential Safety-Related Pump Loss. Specifically, operating the Residual Heat Removal (ND) pumps at flow rates less than 3000 gallons per minute (gpm) will increase the stress on the ND pump motor lower bearings. Current evaluations show that the increased stress on the motor bearing is not great enough to cause undue bearing wear for the short term, approximately 10 years.

Therefore, operating the ND pumps at the proposed lower flow will not impact the operation of the ND system. ND pump flow will be monitored for this increase in bearing wear. If inspection or equivalent pump run time dictate, the bearings will be replarad.

10 CFR 50.92 states that a proposed amendment involves no significant hazards considerations if operation in accordance with the proposed amendment would not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.

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• DISCUSSION, NO SIGNIFICANT HAZARDS ANAINSIS AND ENVIRONMENTAL IMPACT STATEMENT This change, which would allow the' flow requirements-for the ND System to be reduced?to prevent vortexing in the ND System, does not. involve a significant-Lincrease in the probability or consequences of an accident previously evaluated. The reductionfi n flow will not keep the.ND System from fulfilling

-its safety functions. The ND System will continue to remove enough residual-heat-to maintain-the NC System below 140 F, prevent boron: dilution and prevent boron stratification. Two ND pumps (trains) will still be required operable

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when there is less_than 23 feet of water'above the reactor vessel flange. .This-will. ensure that a single failure of the operating residual heat removal pump (train) will not result in a complete loss of ND System capability. This change will reduce the probability of an accident since it will reduce the chances of a loss of the ND System due to vortexing or air entrainment.

The change to the flow requirements for the ND System will not create the.

possibility of a new or different kind of accident from any. accident previously evaluated. The ND System.will still be operated as before except at lower flow rates. The lower flow rates will still allow the ND System to fulfill its safety functions. Therefore, no new or.different kind of accident from any accident'previously evaluated will be created.

The proposed change to.the flow requirements for the ND System will not involve.

a significant reduction in a margin of safety. No functional change is being made to the ND. System. The lowering of'the flow rate requirements will reduce the chances of rendering the ND System inoperable. This will increase the; margin of safety.

Environmental Impact The proposed Technical' Specification change has been reviewed against the

. criteria of 10 CFR 51.22 for the environmental considerations. As shown above, the proposed change does not involve a significant hazards consideration, nor increase the types and amounts of effluents that may be released offsite, nor increase individual or cumulative occupational radiation exposures. Based on this, the proposed Technical Specification change meets the criteria given in 10 CFR 51.22(c)(9) for a categorical exclusion from the requirement for an Environmental Impact Statement.

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