ML20116E942

Proposed Tech Specs Re Reduced Refueling Water Level for Control Rod Latching & Unlatching Re LCO 3.9.10

ML20116E942
Person / Time
Site:	Sequoyah
Issue date:	11/02/1992
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20116E925	List: ML20116E922 ML20116E942
References
NUDOCS 9211100095
Download: ML20116E942 (10)

Text

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REFUELING OPERATICNS 3/4.9.10 WATER LEVEL - REACTOR VESSEL LIMITING CONDITION FOR OPERATION U 3.9.10 At least 23 feet of water shall be maintained over the top of the reactor pressure vessel flange.

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SURVEILLANCE REOUIREMENTS 4.9.10 The water level shall be determined to be at least its minimum required depth within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> prior to the start of and at least once per

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REFUELING 0PERATIONS ,j m

3/4.9.10 WATER LEVEL - REACTOR VESSEL LIMITING CONDITION FOR OPERATION 3.9.10 At least 23 feet of water shall be maintained over the top of the reactor pressure vessel flange, ~-

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ACTION:

(IRA.Hbi With the requirements of the above specification not satisI h%-suspetid all CORC 4tmgTM*cherations involving movement of 57)uel assemblies +e.-cent +ol-rMs- within the- Coquipmyr Seeswee-ves sel, The-prov444 ens-of-Spec 4 f4ca trien-3r0r3-see- no tr- app 44 cab l e,--

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SURVEILLANCE REQUIREV~NTS

' Cw 4.9.10 The water level shall be determiud to be at least its minimum required depth within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> prior to the start of and at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereaf ter during movement of fuel assemblies +c-control rodst WITiilN con %iHD)ENT.

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Insart A as During CORE ALTERATIONS, except during latching and unlatching of control rod drive shafts or,

b. During movement of irradiated fuel asseinblies within containment.

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ENCLOSURE 2 PROPOSED TECllNICAL SPECIFICATION (TS)-CilANGE- -

- SEQUOYAll NUCLEAR PIANT UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328-(TVA-SQN-TS-92-11)~

DESCRIPTION AND JUSTIFICATION FOR -,

RELUCED REFUELING WATER LEVEL FOR CONTROL ROD LATCl!ING AND UNIATCllING ,

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DescrhtlioILof_C10nge WA proposes to modify the Sequoyah Nuclear Plant (SQN) Units 1 and 2 technical specifications (TSs) to revise TS 3.9.10 to provide an exception for contrni rod latching and unlatching in Mode 6 relative to refueling water level requirew.nts. This will be sicomplished by revising the applicability statement to read as follows "a. During CORE ALTERATIONS, except during latching and unlatching of control rod drive shafts or,

b. During movement of irradiated fuel assemblies within containment."

This change will incorporate the same wording for both units that is based on the wording in the recently approved Methodically Engineered. Restructured and Improved Technical Specifications (MERITS) (NUREG-1431). The action statement and surveillance requirements (SRs) associated with the limiting condition for operation (LCO) have been revised to be consistent with this change. A cleanup item is included in this change to delete an exception to TS 3.0.3.

Reasurtlor_ Change The present TS requires 23 feet of water above the reactor pressure vessel '

flange during control rod movement, which includes activities for latching and unlatching the drive urits. The lifLing rig of the upper internals requires a water level of approximately 13 feet or less above the flange for connection to the upper internals. Therefore, the sequence of activities presently required during refueling operations is to flood the cavity to at least 23 feet of water above the flange and uniatch the control rods. This is followed by a draindown to 13 feet or less above the-flange to s.ttach the lifting rig of the upper internals. The next activity la to reflood to at least 23 feet above the flange in preparation for the removal of the upper internals and fuel assembly movement. This same sequence of activities is required in reverse order at the end of core reload.

The performance of the floodup, draindown, and reflood activities is an unnecessary evolution that impacts the refueling outage duration and compounds the complexity of refueling activities. The proposed change would allow the refueling water in the cavity to be brought to an appropriate level where unlatching of control rods and attachment of the lifting rig of the upper internals can be accomplished without any additionni water-level changes. The floodup to at least 23 feet would not be required until movement of irradiated fuel assemblics. This will reduce the duration of these activities by 4 to 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and greatly reduce the complexity of refueling operations by eliminating '

the draindown and reflood evolutions. The same benefit is obtained at the end of core reload such that a total of 8 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of critical path refueling outage time is saved as well as the elimination of a second draindown and-reflood evolution. The other changes provide better consistency with MERITS and eliminate an unnecessary TS 3.0.3 exception. The changes will provide identical wording for both units and thereby eliminate any possible confusion associated with the application of the requirements by the Operations crews.

For the deletion of the exception to TS 3.0.3, the movement of fuel assemblies and control rods is within WA's control; therefore, it can be suspended at any time, negating the need for this exception.

JustiLicatioILloLChange The proposed exception for control rc3 latching and unlatching is justified on the basis of this activity's inapplicability to the postulated fuel-handling accident scenario for which the 23-foot requirement is specified. There is no potential for such an accident during these activities. Control rod latching and unlatching occur while the upper internals are in place over the core. 1his configuration prevents full withdrawal of control rods; and because of the weight of the upper intervals above the fuel assemblies, no t'uel movement can be performed. This would limit concerns to the small control rod movement utilized to verify the latched or unlatched condition. At most, this movement could only result in friction between the control rods and the fuel assemblies, but cannot create significant forces that could damage the fuel rods and release the gap activity. The activities associated with the latching and unlatching of the control rods would be considered a core alteration based on the small movements of-the control rods, but would be addressed by an exception to the proposed TS chango.

The accident a.nalysis that is related to core alteration and fuel movement activities is the fuel-handling accident that results from major damage to an irradiated fuel assembly. This postulated accident is discussed in Sections 15.4.5 rnd 15.5.6 of the SQN Final Safety Analysis Report. The cause of this accident is postulated as the dropping of an irradiated fuel assembly, resulting in the rupture of the cladding of all the fuel rods in the assembly. To mitigate the consequences of this event, the TSs require 23 feet of water above the reactor pressure vessel flange, which is the highest point that fuel assemblies are transported over within containment. This depth of water provides for the removal of 99 percent of the iodine gap activity assumed to be released during the fuel-handling accident. The proposed TS change continues to require the 23-foot refueling water level requirement during all setivities and conditions for which dropping of an irradiated fuel assembly is possible. The exception to this level requirement for control rod latening and unlatching is acceptable because there is no po6sibility for dropping a fuel essembly or causing sufficient damage to a fuel assembly, resulting in the release of fuel rod gap activity. Therefore, the 23-foot requirement for refueling water level is not necessary during control rod latching and unlatching.

The water level requirement in TS 3.9.10 is only provided for iodine removal during mitigation of a fuel-handling accident. Other considerations for personnel radiation exposure, shutdown margin, er operational activities are not provided for by this requirement. With the approval of the proposed TS change by NRC, the water level for control rod latching and unlatching will be controlled administratively to accomodate radiological considerations and operational activities associated with refueling operations, i.e., as is currently done for L

activities such as upper internals lifting rig attachment. The ,

radiological considerations will be the primary input for determining the l

sppropriate water level based on concepts that are as low as reasonably achievable, minimization-of hot particles, and control of airborne radioactivity.

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The action-requirements and SRs have been revised to be consistent with the proposed applicability changes previously described. In addition, the TS 3.0.3 exception for the action statement is being. removed becauss' it providea no benefit for a Mode 6 LC0 when suspension of fuel assembly and control-rod movement can be achieved.

Enyhonmental_lm2act Evaluation The proposed change request does not involve an unreviewed environmental question because operation of SQN Units 1 and 2 in accordance with this change would not:

1. Result in a significant increase in any adverse environments 1 impact previously evaluated in the Final Environmental Statement (FES) as modified by the staff's testimony to the Atomic Safety and Licensing _

Board, supplements to the FES, environmental irgset appraisals, or decisions of the Atomic Safety and Licensing board.

2. Result in a significant change in effluents or power levels.

3. Result in matters not previously reviewed in.the licensing basis,for SQN that may have a significant environmental impact. -

Enclosure 3 ,

PROPOSED TECHNICAL SPECIF'ICATION (TS) CHANCE SEQUOYAH-NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 5')-327 AND 50-328-(TVA-SQN-TS-92-11 DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION

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3 Significant Hazards Evaluation TVA has evaluated the proposed technical specification (TS) change and has determined that it does not represent a significant hazards consideration based on criteria established in 10 CFR 50.92(c).

Operation of Sequoyah Nuclear Plant (SQN) in accordance with the proposed amendment will not:

1. Involve a significant increase in the probability or consequences of an accident previously esaluated.

This TS change continues to require at least 23 feet of refueling water above the reactor pressure vessel flange for core alteration and movement of irradiated fuel assemblies as required by the existing TS 3.9.10, and does not affect the probability or consequences of an accident. The 23-foot water-level requirement ic based on lodine removal for the postulated fuel-handling accident involving dropping and rupture of an irradiated fuel assembly that the latching and unlatching activities could not create.

Additionally, because the upper internals are in place during latching and unlatching activities, the full withdrawal of control rods or movement of fuel assemblies car.aot be performed, and the conditions postulated to result in a fuel-handling accident are not-possible. Therefore, this exception for refueling water level during control rod latching and uniatching does not increase the probability of an accident and in fact, the plant conditions required for this activity do not result in configurations that are necessary to create the postulated accident. The consequences of an accident are not increased because the 23 feet of water above the reactor pressure vessel flange is still maintained for iodine removal except during control rod latching and unlatching when no postulated accident could occur. All other changes are clarifications, along with the deletion of the TS 3.0.3 exception, that do not affect the intent or operational impact of this specification and therefore will not increase the probability or consequences of an accident.

2. Create the possibility of a new or different kind of accident from any previously analyzed.

The refueling water-level requirements for core alterationa and movement of irradiated fuel assemblies, excluding control rod latching and unlatching, are unchanged. These activities have been previously analyzed for a fuel-handling accident. The exception to the refueling water-level requirement for cont':o1 rod latching and .

unlatching does not alter the physical manipriations for refueling activities involving core alterations or fuel movement and does not create any conditions that could create an accident. The refueling water-level requirements are provided for mitigation of accidents and do not have an effect on accident generation; therefore, an exception that allows refueling. water level below 23 feet will not create the potential for an accident. This change, along with the clarifications and TS 3.9.3 exception deletion, does not create the possibility of a new or different kind of accident from any previously evaluated.

".. , 3. Involve a significant reduction in a margin of safety.

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1 All margins assumed in the accident analysis for fuel-handling accidents are maintained ir this change because 23 feet of water is still required-for the removal of iodine activity during_ core alterations and movement of irradiated' fuel assemblies.- The exception to this water-level requirement is only allowed during-control rod latching and unlatching when the potential for a fuel-handling accident does not exist. Thereform, this change will not reduce the margin of safety and the margin to 10 CFR 100 dose limits is not affected.

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