ML20211B705

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Proposed Tech Specs Revising Reactor Core Spiral Reloading Pattern to Begin Around SRM
ML20211B705
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 08/18/1999
From:
VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20211B702 List:
References
NUDOCS 9908250064
Download: ML20211B705 (11)
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Text

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, ' VI:nMoNT YANht.E Nt ci. Erst Powiat Coniaostriu>N Docket No. 50-271

. . BVY 99-104 l

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Attachment 3 Vermont Yankee Nuclear Power Station .

Proposed Technical Specification Change No. 223 Spiral Core Loading Around a Source Range Monitor Marked-up Version of the Current Technical Specifications and Bases I

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9908250064 990818 PDR ADOCK 05000271 P PDR l 1

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VYNPS 3.12' LIMITING CONDITIONS FOR 4.12 SURVEILLANCE REQUIREMENTS OPERATION

3. ~ Prior to spiral Prior to spiral unloading unloading, the SRNW or reloadir.g, the SRMs shall be proven shall be functionally operable as stated in tested. Prior to spiral Sections 3.12.B.1 and reloading, the SRMs shall 3.12.B.2 above, be checked for neutron l

however, during spiral response, unloading the count

rate may drop below 3 eps.
4. Prior to spiral -

reloading, two diagonally adjacent fuel assemblies, which have previously accumulated exposure in the reactor, shall be loaded into itjurus i (descanaefd Wore pos;.tions next to each L of the 4 SRMs to obtain the required 3 eps.

l Until these eight bundles have been-loaded, the 3 cps requirer, ant is not necessary.

C. Puel Storace Pool Water C. Puel Storace Pool Water Level fd Whenever irradiated fuel is Whenever irradiated fuel is stored in the fuel storage stored in the fuel storage pool the pool water level pool, the pool level shall shall be maintained at a be recorded daily.

level of at least 36 feet.

1 Amendment No. 69, 77 231

VYNPS I

. 3.12 LIMITING CONDITIONS FOR 4.12 SURVEILLANCE REQUIREMENTS OPERATION

b. The core may be spirally reloaded to either the original configuration or a different configuration in the reverse sequence of that used to unload, with the exception that two (2)

, diagonally adjacent fuel assemblies, which have previously accumulated exposure in the i reactor, shall be loaded int _oJDiETB

[dationatedfcore l positions next to each of the four (4) SRMs to obtain the required 3 eps. Until these eight (8)

.- bundles have been loaded, the 3 cps

> requirement is not necessary.

Following insertion of the initial eight (8) bundles, the reactor will be

'N spirally reloaded n

" * " _d " SR

" _ jM Cfdi'4h*:"F until the core is fully loaded.

.: At least 50% of c.

the fuel assemblies to be reloaded into the core shall have previously accumulated a minimum exposure of 1000 Hwd/T.

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234 i Amendment No. 69, 77

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'3.12 & 4.12 REFUELING i

A. During refueling operations, the reactivity potential of the core is '

being altered. It is neenssary to require certain interlocks and restrict certain refueling procedures such that there is assurance that I inadvertent criticality does not occur.

To minimize the possibility of loading fuel into a cell containing no control rod, it is required that all control rods are fully inserted when fuel is being loaded into the reactor core. This requirement ,

assures that during refueling the refueling interlocks, as designed, I will prevent inadvertent criticality. The core reactivity limitation of Specification 3.3 limits the core alterations to assure.that the resulting core loading can be controlled with the Reactivity Control System and interlocks at any time during shutdown or the following operating cycle.

The addition of large amounts of reactivity to the core is prevented by operating procedures, which are in turn backed up by refueling interlocks on rod withdrawal and movement of the refueling platform.

When the mode switch is in the " Refuel" position, interlocks prevent the refueling platform from being moved over the core if a control rod is withdrawn and fuel is on a hoist.

Likewise, if the refueling platform is over the core with fuel on a hoist, control rod motion is blocked by the interlocks. With the mode switch in the refuel position, only one control rod can be withdrawn.

B. The SRMs are provided to monitor the core during periods of station shutdown and to guide the operator during refueling operations and station startup. Requiring two operable SRMs in or adjacent to any core quadrant where fuel or control rods are being moved assures adequate monitoring of that quadrant during such alterations. The requirement of 3 counts per second provides assurance that neutron flux is being monitored. Under the special condition of complete spiral core unloading, it is expected that the count rate of the SRMs will drop below 3 cps before all the fuel is unloaded. Since there will be no reactivity additions, a lower number of counts will not present a hazard. When all of the fuel has been removed to the spent fuel storage pool, the SRMs will no longer be required. Requiring the SRMs to be operational prior to fuel removal assures that the SRMs are operable and can be relied on even when the count rate may go below 3 cps.

Prior to spiral reload, two diagonally adjacent fuel assemblies, which have previously accumulated exposure in the reactor, will be loaded into Ehoet dediggej core positions next to each of the 4 SRMs to obtain the required 3 cps. Exposed fuel continuously produces neutrons by spontaneous fission of certain plutonium isotopes, photo fission, and photo disintegration of deuterium in the moderator. This neutron production is normally great enough to meet the 3 cps minimum SRM requirement, thereby providing a means by which SRM response may be demonstrated before the spiral reload begins. During the spiral reload, the fuel will be loaded in the reverse sequence that it was i

unloaded with the exception of the initial eight (8) fuel assemblies

! which are loaded next to the SRMs to provide a means of SRM response.

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Amendment No. 44, 69, 44, 164 237

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, VYNPS

. , 3 333, 3.12 ts 4.12 (Cont'di

c. To assure that there is adequate water to shield and cool the irra-diated fuel assemblies stored in the pool, a =4a4-= pool water level is established. This minimum water level of 36 feet is established because it would be a significant change from the nounal level, well above a level to assure adequate cooling (just above active fuel) .

D. During certain periods, it is desirable to perform maintenance on a single control rod and/or control rod drive. This specification provides assurance that inadvertent criticality does not occur during such maintenance.

The maintenance is performed with the mode switch in the " Refuel

  • position to provide the refueling interlocks normally available during refueling operations as explained in Part A of these Bases.

Refueling interlocks restrict the movement of control rods and the operation of the refueling equipment to reinforce operational procedures that prevent the reactor from becoming critical during refueling operations. During refueling operations, no more than one control rod is permitted to be withdrawn from a core cell containing one or more fuel assemblies. The refueling interlocks use the

" full-in'. position indicators to determine the position of all control' rods. If the " full-in' position signal is not present for every control rod, then the 'all-rods-in' permissive for the refueling equipment interlocks is not present and fuel loading and-control rod withdrawal is prevented. The refuel position one-rod-out interlock will not allow the withdrawal of a second control rod. The requirement that an adequate shutdown margin be determined with the control rods remaining in service ensures that inadvertent critica-

. lity cannot occur during this maintenance. Disarming the directional control valves does not inhibit control rod scram capability.

\ E. The intent of this specification is to permit the unloading of a portion of the reactor core for such purposes as inservice inspection h requirements, examination of the core support plate, control rod, control rod drive maintenance, etc. This specification provides assurance that inadvertent criticality does not occur during such operation.

This operation is performed with the mode switch in the " Refuel

  • position to provide the refueling interlocks normally available during refueling as explained in the Bases for Specification 3.12.A.

In order to withdraw more than one control rod, it is necessary to bypass the refueling interlock on each withdrawn control rod which ,

prevents more than one control rod from being withdrawn at a time.

The requirement that the fuel assemblies in the cell controlled by the control rod be removed from the reactor core before the interlock can be bypassed ensures that withdrawal of another control rod does l not result in inadvertent criticality. Each control rod essentially provides reactivity control for the fuel assemblies in the cell associated with that control rod. Thus, removal of an entire cell (fuel assemblies plus control rod) results in a lower reactivity potential of the core.

One method available for un:oadiaa or reloading the core is the _

spiral unload / reload.fA sp: 1 unloading pact is one by which ei e outermost cel (four fuel bund surrounding a co ol Truel in

' rod) removed.first. nioading contin by unloading the r ing outermost el by cell spira g inward towards e center b s*d 'c 1 which is the loading, with se cell removed. spiral reloading i e exception thaJ. wo (2) diagonally -core, everse acent of I bundles, whic ve previously ceumulated exposure are placed nex o each of the 4 before the actu spiral reloadi

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e spiral reload en begins in the e er cell and sp als  !

begins.

Qutwardungtil the core if ully loaded.  ;

f 238 Amendment No. M.

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vani<>si vom. .wco.w n,wn c<,,<>...im i<,s i

l Insert 1, Bases 3.12.E, page 238 Spiral reloading and unloading sequences encompass reloading or unloading a cell on the edge of j a continuous fueled region (the cell can be reloaded or unloaded in any sequence.) The pattern

begins (for reloading) and ends (for unloading) around a single SRM. The spiral reloading l

pattern is the reverso of the unloading pattern, with the exception that two diagonally adjacent bundles, which have previously accumulated exposure in-core, are placed next to each of the four SRMs before the actual spiral reloading begins. The spiral reload can be to either the o:iginal

configuration or a different configuration.

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Vi HuoNT YANKl.n Nrce.r.Au Pown it CosmonAlsoN Docket No. 50-271 BVY 99-104 1

Attachment 4 Vermont Yankee Nuclear Power Station Proposed Technical Specification Change No. 223 Spiral Core Loading Around a Source Range Monitor Retyped Technical Specifications and Bases Pages

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.VYNPS l

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l 3.12 LIMITING CONDITIONS FOR 4.12 SURVEILLANCE REQUIREMENTS OPERATION-

3. Prior to spiral Prior to spiral unloading or unloading, the SRMs shall reloading, the SRMs shall be l be proven operable as functionally tested. Prior stated in Sections to spiral reloading, the SRMs 3.12.B.1 and 3.12.B.2 shall be checked for neutron above, however, during response.

spiral unloading the count rate may drop below l 3 cps.

4. Prior to spiral '.

l reloading, two diagonally adjacent fuel assemblies, which=have previously accumulated exposure in the reactor, shall be loaded into core

! positions next to each of the 4 SRMs to obtain the required 3 cps. Until these eight bundles have been loaded, the 3 eps requirement is not '

necessary.

( C. Fuel Storage Pool Water Level C. Fuel Storage Pool Water Level l Whenever irradiated fuel is Whenever irradiated fuel is stored in the fuel storage stored in the fuel storage pool the pool water level pool, the pool level shall be shall be maintained at a recorded daily.

level of at least 36 feet.

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(= Amendment No. H,.M 231 i

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.. _ VY! TS

.3.12 LIMITING CONDITIONS FOR 4.12 SURVEILLANCE REQUIREMENTS OPERATION

b. The core may be spirally reloaded to either the original Lconfiguration or a-different configuration in the reverse sequence of that used to unload, with the exception that'two (2) diagonally adjacent fuel. assemblies, which have previously accumulated exposure.

.in the reactor, shall be loaded into core positions next to each of the four (4) SRMs to obtain i the required 3 cps.

Until these eight (8) bundles have been loaded, the 3 cps requirement is not necessary.

Following insertion i of the initial eight (8) bundles, the  !

reactor will be spirally reloaded around an SRM until the core is fully

. loaded, c; At least 50% of the fuel assemblies to be reloaded'into the core shall have previously accumulated a minimum exposure of 1000 Mwd /T.'

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. Amendment No. 64,- M 234

'

3.'12 & 4.12 REFUELING f l

A. During refueling operations, the reactivity potential of the core is '

being altered. It is necessary to require certain interlocks and restrict certain refueling procedures such that there is assurance that

)

inadvertent criticality does not occur.

To minimize the possibility of loading fuel into a cell containing no control rod, it is required that all control rods are fully inserted when fuel is being loaded into the reactor core. This requirement assures that during refueling the refueling interlocks, as designed, will prevent inadvertent criticality. The core reactivity limitation of Specification 3.3 limits the core alterations to assure that the resulting core loading can be controlled with the Reactivity Control System and interlocks at any time during shutdown or the following I operating cycle. l The addition of large amounts of reactivity to the core is prevented by operating procedures, which are in turn backed up by refueling interlocks on rod withdrawal and movement of the refueling platform.

When the mode switch is in the " Refuel" position, interlocks prevent the refueling platform from being moved over the core if a control rod is withdrawn and fuel is on a hoist.

Likewise, if the refueling platform is over the core with fuel on a ]

hoist, control rod motion is blocked by the interlocks. With the mode l switch in the refuel position, only one control rod can be withdrawn. l B. The SRMs are provided to monitor the core during periods of station shutdown and to guide the operator during refueling operations and station startup. Requiring two operable SRMs in or adjacent to any core quadrant where fuel or control rods are being moved assures adequate monitoring of that quadrant during such alterations. The requirement of 3 counts per second provides assurance that neutron flux is being monitored. Under the special condition of complete spiral core unloading, it is expected that the count rate of the SRMs will 1 drop below 3 cps before all the fuel is unloaded. Since there will be no reactivity additions, a lower number of counts will not present a hazard. When all of the fuel has been removed to the spent fuel storage pool, the SRMs will no longer be required. Requiring the SRMs to be operational prior to fuel removal assures that the SRMs are operable and can be relied on even when the count rate may go below 3 cps.

Prior to spiral reload, two diagonally adjacent fuel assemblies, which have previously accumulated exposure in the reactor, will be loaded into core positions next to each of the 4 SRMs to obtain the required 3 cps. Exposed fuel continuously produces neutrons by spontaneous fission of certain plutonium isotopes, photo fission, and photo j disintegration of deuterium in the moderator. This neutron production is normally great enough to meet the 3 cps minimum SRM requirement, thereby providing a means by which SRM response may be demonstrated

-before the spiral reload begins. During the spiral reload, the fuel will be loaded in the reverse sequence that it was unloaded with the exception of the initial eight (8) fuel assemblies which are loaded next to the SRMs to provide a means of SRM response.

Amendment No. M, M, -M, M4 237 j

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VYNPS BASES: 3.12 & 4.12 (Cont'd)

C. To assure that there is adequate water to shield and cool the irra-

. . diated fuel assemblies stored in the pool, a minimum pool water level is established. This minimum water level of 36 feet is established because it would be a significant change from the normal level, well above a level to assure adequate cooling (just above active fuel) .

D. During certain periods, it is desirable to perform maintenance on a single control rod and/or control rod drive. This specification provides assurance that inadvertent criticality does not occur during such maintenance.

The maintenance is performed with the mode switch in the " Refuel" position to provide the refueling interlocks normally available during refueling operations as explained in Part A of these Bases. Refueling interlocks restrict the movement of control rods and the operation of the refueling equipment to reinforce operational procedures that prevent the reactor from becoming critical during refueling operations.

During refueling operations, no more than one control rod is permitted to be withdrawn from a core cell containing one or more fuel (

assemblies. The refueling interlocks use the " full-in" position indicators to determine the position of all control rods. If the

" full-in" position signal is not present for every control rod, then the "all-rods-in" permissive for the refueling equipment interlocks is not present and fuel loading and control rod withdrawal is prevented.

The refuel position one-rod-out interlock will not allow the withdrawal of a second control rod. The requirement that an adequate shutdown margin be determined with the control rods remaining in service ensures j that inadvertent criticality cannot occur during this maintenance.

Disarming the directional control valves does not inhibit control rod scram capability.

E. The intent of this specification is to permit the unloading of a portion of the reactor core for such purposes as inservice inspection requirements, examination of the core support plate, control rod, control rod drive maintenance, etc. This specification provides assurance that inadvertent criticality does not occur during such operation.

This operation is performed with the mode switch in the " Refuel" l position to provide the refueling interlocks normally available during j refueling as explained in the Bases for Specification 3.12.A. In order to withdraw more than one control rod, it is necessary to bypass the refueling interlock on each withdrawn control rod which prevents more than one control rod from being withdrawn at a time. The requirement that the fuel assemblies in the cell controlled by the control rod be removed from the reactor core before the interlock can be bypassed ensures that withdrawal of another control rod does not result in i inadvertent criticality. Each control rod essentially provides  !

reactivity control for the fuel assemblies in the cell associated with l that control rod. Thus, removal of an entire cell (fuel assemblies plus control rod) results in a lower reactivity potential of the core.

One method available for unloading or reloading the core is the spiral unload / reload. Spiral reloading and unloading encompass reloading or unloading a cell on the edge of a continuous fueled region (the cell can be reloaded or unloaded in any sequence.) The pattern begins (for reloading) and ends (for unloading) around a single SRM. The spiral reloading pattern is the reverse of the unloading pattern, with the exception that two diagonally adjacent bundles, which have previously accumulated exposure in-core, and placed next to each of the four SRMs before the actual spiral reloading begins. The spiral reload can be to either the original configuration or a different configuration.

Amendment No. -M, -14 8 238 L

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