ML20101S346

Proposed TS Section 3.8 Re Core Alterations During Refueling & Fuel Handling

ML20101S346
Person / Time
Site:	Prairie Island
Issue date:	07/13/1992
From:	NORTHERN STATES POWER CO.
To:
Shared Package
ML20101S332	List: ML20101S331 ML20101S338 ML20101S346
References
NUDOCS 9207170054
Download: ML20101S346 (18)

Text

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, Exhibit B Prairie Island Nuclear Generating Plant License Amendment Request Dated July 13, 1992 Proposed Changes Marked Up On Existing Technical Specification Pages Exhibit B consists of existing and new. Technical Specification pages with the _

proposed changes highlighted.on those pages. The existing pages affected by this License Amendment Request are listed below:

TS.3.8 1 TS.3.8 2 TS.3.8 3 Table TS.4.1 2A B.3.8 1 B.3.8 2 B.3.8 3 9207170054.920713 DR p :ADOCK 05000282 PDR

TS.3.8 1 3.s - RETUELING AND TUEL llANDLING 6ppJ ie nbil ity Applies to operating limitations associated with fuel handling operations, CORE ALTERATIONS, and crane operations in the spent fuel pool enclosure.

Objectives To ensure that no incident could occur during fuel handling, CORE ALTERATIONS and crane operations that would affect public health and safety.

Spf.sj fl e a t ion A. Core Alterallena

1. During CORE ALTERAT10h) the following conditions shall be satisfied (except as specified in 3.8.A.2 and 3 below):

a . The-wtut t eent-hot +h-+mt-et--h+ast-wwwloor-hwelmr*w nel-el+-4*ek sha44-4+e-e4*eed . %-ed4i+4wer.+ t I e a e tn>no--isel ath.*-valvo-oluill-be OPERAM&e r-4*oked-*1<*eed-44+-ee eh-t hw+-wh4 +h-pene+ rat +e-4 he cent-a4 nneent-end-p rev44*e-e-41u+et-pat h-h :: n t n !4 ment-son.oepher+

te-t4 e-out+4 der The containment. building penetrations'shall be ini the following status:

12 Thef equipment hatch closed ^and heldfln' place ibyfa" minimum 'ofl"four bolts,

2. "A"niinimum of one" door"in;eact(airlobk ia closiod,~And 3, Each penetration providingTdirect" access from the containment atmosphere to the-outside atmouphere cha11'be. either:

'a)' closed by_an isolation' valve, blind flange ~or manual-valve; or b) Ee capabic ^of. being closed byin OPERABLE autotaatic cont.ainment purge.or inservice purge isolacion. valve;

4. If the' Auxiliary:BuildingLSpecialfVent11'ation Systemlis inoperable, each penetration ~ providing direct access. frora'the containment atmosphere to-the' Auxiliary Building Special Ventilation Zone 'ch'all be closed by, an . isolation valve t blind flange ~or. manual'. valve.

5~.fIf the ' Shield Building Ventilation System is inoperable, each penetration providing-direct access from'the containmant.

atmosphere to the shield building annulus shall- be citsed by..'an isolation valve, blind flange or taanual valvei

b. Radiation levels in the fuel 1. Ing areas of the containment shall be monitored continuous 13 "t .

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TS.3.8 2 i

c. The core suberitical neutron flux shall be continuously monitored by at least two neutron monitors, each with continuous visual indication in the control room and one with audible indication in the containment, which are in service whenever core geometry is being changed. When core geometry is not being changed, at least one neutron flux monitor shall be in se; / ice.

d. The plant shall be in the REFUELING condition.

3. 8. A!1 ~. e . During movement of fuel assemblies or control rods out of the reactor vessel, at least 23 feet of water shall be maintained above the reactor vessel flange. The required water level shall be verified prior to moving fuel assemblies or control rods and at least once every day while the cavity is flooded. _

3.S.^ 1.f. At least one residual heat removal pump shall be OPERABLE and running. The pump may be shut down for up to one hour to facilitate movement of fuel or core components,

g. If the water level above the top of the reactor vessel flange is less than 20 feet, except for control rod unlatching / latching operations or upper internals removal / replacement, both residual heat removal loops shall be OPcRABLE.

h. Direct communication between the control room and the operating floor of the containment shall be available whenever CORE ALTERATIONS are t, ing place.

i. No movement of irradiated fuel in the reactor shall be made until the reactor has been suberitical for at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

j. The radiation monitors which initiate isolation of the Contain-ment Purge System shall be tested and verified to be OPERABLE _

prior to CORE ALTERATIONS.

K. iThe mantpulator. crane shall be OPERABLE for the movement of_ fuel assemblies.

2. If any of the above conditions are not met, CORE ALTERATIONS shall cease. Work shall be initiated to correct the violated conditions so that the specifications are met, and no operations which may increase the reactivity of the core shall be performed.

3. If Specification 3.8.A.1.f or 3.8.A.1.g cannot be satisfied, all fuel handlin6 operations in containment shall be suspended, the requirements of Specification 3.8 A.1.a shall be satisfied, and no reduction in reactor coolant boron concentration shall be made.

4 TS.3.8 3 1

3.8.B. Fuel Handline Operations

1. During fuel handling operations in. spent fuel ' pool.? area the following conditions shall be satisfied:

a. Radiation levels in the spent fuel storage pool area shall be monitored continuously durin6 fuel handling operations,

b. .Fr4+r : Nel - hand 14eg-eperet ere . be'. - hand 14ee-erenee-+ha14 be lec4-t:0 ted fee.4PTRABILITY cf- 1 to44-swl4:ber , - !*&er4+ eke end-*1eree r The7s pe nEfds1 Tgio oli fue lj lMn dl in[H.an6?'ahall !;;b e OPERABLE *forithemovementiofsfue1Tassemblies;-- ~ _

c. LA minimum boron concentration of 1800 ppm shall be maintained.

In the spent _ fuel pool whenever a spent. fuel cask containing fuel is located in the spent fuel pool. ,

2.- If any of the conditions in 3.8.B.1, above, cannot be met. suspend alt . fuel handling eperations inlthe'spentJael"piso1'spss and initiate the actions necessary to re establish compliance with the requirements of 3.8.B;1.

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Tcble TS.4.1 2A  !

(Page;1 Toff 2) l MINIMUM FREOUENCIES FOR EOUIPMENT TESTS Iggt Frecuency i

1. Control P.od Assemblies Rod drop times All-rods during each refueling of full length shutdown or following each m.

rods removal of the reactor vessel head; affected rods following maintenance on or_ modification j to the control rod drive system ~

which could affect performance of those specific rods ~ ,t 12 . . Control! Rod Assemblies Partial movement ~ Every 2 weeks of all roda

3. < Pressurizer Safety -Set point. Per ASME Code,Section XI Vr * 'es . Inservico Testing Program

4. Main Steam Safety Set point Per ASME Code,Section XI Valves inservice-Testing Program-

-5. Reactor Cavity -Water level Prior to moving fuel assemblies or control rods and at least--

once every day while the cavity is floodep.

6. - Pressurizer PORV Functional Quarterly Block Valves-

7. Pressurizer PORVs Functional Every 18' months

8.. Deleted 1

9. Primary System Leakage Evaluate- Daily

'10. -Deleted 11'.1' Turbine;stop valves. Functional See (1)

_ governor valves, and-intercept. valves.

(Part of; turbine-overspeed protection.).

42. Dale:ci

(1)-Turbine stop. valves, governor' valves and intercept valves are to be tested at Ea(frequency con.tistent with the methodology presented in WCAP 11525 "Probabilistic Evaluation of Reduction in Turbine Valve test Frequency", and in accordance with the established'NRC acceptance criteria for the probability of a turbine missile

, ejection incident of 1;0x10~5 per. year. In no case shall the turbine valve test interval exceed one year.

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Table TS.4.1 2A (Page 2'of 2)

HINIMlH FREWE!?CIES FO[L10VIPMENT TESTS Irig Frecuensy

12. Manipulator Crane Load-test'for On'ce 'during ea'ch refueling OPERABILITY of outage prior to the1 start limtt switchen7 of CORE ALTERATIONS) interlocks and alarms 13' Spent Fuel Pool

, Load test'for Prior to' fuel. handling Puel' Handling Crane OPERABILITY of operations if-not tested in limit switches, the previous 3 months.

interlocks and alarms

B.3.8 1 3.8 REPVELING AND FUEL HANDLING Bases The equipment and general procedures to be utilized during refueling are discussed in the FUSAR. Detailed instructions, the precautions specified above, and the design of the fuel handling equipment incorporatitig built in interlocks and safety features, provide assurance that no incident could occur during CORE ALTEP,ATIONS that would result in a hazard to public health and safety (Reference 1).

The rrequirottents for@ntainment penetration" closure" ensure that n' release of fission product radioactivity lwithin:contaitment due' to a fuel handling hecident will be restricted from escaping directly(to the envirotunent.

Closure ; restrictions are only.. required for. cuneainiuent penetrations: th t provide' direct unfiltered access; from' containment; atmosphere .to outside ntmosp_hp re .

- Thsre7srEn6Talosufofrestrictions'dstf ag CORE l ALTERATIONS ^!nn~containmeht penetrations;that provide!accessifrors'the: containment atmosphere 71nto areas' protected by.0PERABLE automaticisafeguardo[ ventilation:systemsfwhich actuateLon'high radiation and filter allireleases to the envirotunent through particulate . absolute charcoal filterny No closure restrictioiii

'are necessary for those: penetrations because(any radiological, releases to those' areasifollowing a fuel handlingL accident;in< containment:would be released to the environment viaLafparticulate; absolute charcoal! filtration systemh The; particulate absolute a charcoalf filtr,ation of; thel fissioni productfradioactivity released during a design basis?fue1Lhandling accidsntlnlcontainmentwouldmaintAin;offsite; radiatio.nexposuresNell i

within4;the; tequirements of;10, CFR Parti 100; for penetrationslto~ be7 open'into the' r Shield Buildinf AnnulusTduring' CORE ALTERATION 9;-the Shield Building Ventilation lSystom<shall be OPERABLE'and for penetrations.to be'open into;thel Auxiliary building Special Ventilation' Zone during CORE ALTERATIONS Jthe .AuxilisrylBuildingf Specisi VentilationLSystem shall be;0PERABLE.1 Whenever changes are not being made in core geometry, one flux monitor is sufficient. This permits maintenance of the instrumenta-tion. Continuous monitoring of radiation levels and neutron flux provides immediate indication of an unsafe condition. The residual heat removal yump is used to maintain a uniform boron concentration.

Under rodded and unrodded conditions, the K.tr of the reactor must be less than or equal to 0.95 and the boron concentration must be greater than or equal to 2000 ppm. Periodic checks of refueling water boron concentration insure that proper shutdown margin is maintained.

3.8.A.1.h allows the control room operator to inform the manipulator operator of any isopending unsafe condition detected from the main control board indicators during fuel movement.

No movement of fuel in the reactor is permitted until the reactor has been suberiticel for at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to permit decay of the fission products in the fuel, The delay time is consistent with the fuel handling accident' analysis (Reference 2).

B.3.8 2 3.8 REFUELING AND ITEL HANDLING hatti continued Fuel will not be inserted into a spent fuel cask unless a minimum boron i concentration of 1800 ppm is present. The 1800 ppm will ensure that kert for the spent fuel cask, including statistical uncertainties, will be less than or equal to 0.95 for all postulated arrangements of fuel within the cask.

The number of recently discharged assemblies in Pool No. I has been limited to 45 to provide assurance that in the event of loss of pool cooling capability, at least eight hours are available under worst case conditions to make repairs until the onset of boiling.

The Spent Fuel Pool Special Ventilation System (Reference 3) is a safeguards system which maintains a negativn pressure in the spent fuel enclosure upon detection of high area radiation. The Spent Fuel Pool Normal Ventilation System is automatically isolated and exhaust air is drawn through filter modules containing a roughing filter, particulate filter, and a charcoal filter before discharge to the environment via one of the Shield Building exhaust stacks. Two completely redundant trains are provided. The exhaust fan and filter of each train are shared with the corresponding train of the Containment In-service Purge System. High efficiency particulate absolute (llEPA) filters are installed before the charcoal adsorbers to prevent clogging of the iodine adsorbers in each SFPSVS filter train. The charcoal adsorbers are installed to reduce the potential release of radioiodine to the environment.

During movement of irradiated fuel assemblies or control rods, a water level of 23 feet is maintained to provide sufficient shielding.

The water level may be lowered to the top of the RCCA drive shafts for latching and unlatching. The water level may also be lowered below 20 feet for upper internals removal / replacement. The basis for these allowance (s) are (1) the refueling cavity pool has sufficient level to allow time to initiate repairs or emergency procedures to cool the core, (2) during latching / unlatching and upper internals removal / replace-ment the level is closely monitored because the activity uses this level as a reference point, (3) the time spent at this level is minimal.

The requirements for the storage of low burnup fuel in the spent fuel pool ensure that the spent fuel pool will remain subcritical during fuel storage. Fuel stored in the spent fuel pool will be limited to a maximum enrichment of 4.2 weight percent U 235. It has been shown by criticality analysis that the use of the three out of four storage configuration will assure that the K,tr will remain less than 0.95, including uncertainties, when fuel with a maximum enrichment of 4.25 weight percent U-235 and average assembly burnup of less than 5,000 MWD /MTU is stotad in the spent fuel pool.

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B.3.8-3 3.8 REFUELING AND FUEL HANDLING Pases continued ~

The requirement for maintaining the spent fuel pool boron concentration greater than 500 ppin whenever fuel with average assembly burnup of less w than 5,000 MWD /MTU is stored in the spent fuol pool ensures that K.gr for the' spent fuel pool will remain less than 0.95, including uncertainties.

even if a fuel assembly is inadvertently inserted in the empty cell of the ,

three out of four storage configuration.

References

1. USAR, Section 10.2.1.2-2.--USAR, Section 14.5.1

3. USAR,:Section 10.3.7 J

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m, Exhibit C Prairie Island Nuclear Generating Plant License Amendment Request Dated July 13, 1992 Revised Technical Specification Pages Exhibit C consists of revised and new pages for the Prairie Island Nuclear Generating Plant Technical Specification with the proposed changes incorporated. The revised and new pages are listed below:

TS.3.8 1 TS.3.8 2 TS.3.8 3 Table TS.4.1 2A (Page 1 of 2)

Table TS.4.1 2A (Page 2 of 2)

B.3.8-1 B.3.8 2 B.3.8 3

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,i TS.3.8 1

- 3.8 RETUELING AND TUEL HANDLING Aeolicability m

SE . Applies to operating limitations associated with fuel handling operations.

- CORE: ALTERATIONS, and: crane operations in the spent fuel pool enclosure.

. 0bjectivtg To ensure that no incident could occur during fuel handling, CORE ALTERATIONS asul crane. operations that would affect public health and safety.

Specification ,

A,  : Core Alteration 1

1. During CORE ALTERATIONS the following conditions shall be satisfied

'(except as specified in 3.8.A.2 and-3 below):

a? The-containment building penetrations shall be in the following

-sta;ust

1. The: equipment-hatch closed and held in place by a minimum of four bolts, a-

2. A' minimum of one. door [in each airlock is closed, and

3. Each' penetration providing direct access-from the containment atmosphere to:the outside atmosphere shall be either:

c a) Closed by an isolation valve, blind flange or manual valve, or-b) Be capable of being closed by an OPERABLE automatic containment' purge or inservice purge isolation valve.

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4. If the Auxiliary Building Specia1' Ventilation System is

, -inoperable, each penetration providing direct access from the containment atmosphere to the Auxiliary Building'Special Ventilation Zone shall be closed by an isolation valve, blind flange or' manual. valve.

'5.11f the Shiild Building' Ventilation System is inoperable, each 4 penetration providing direct access from the containment atmosphere to the shield building annulus shall be closed by an

' isolation valve', blind flange.or manual valve..

b. Radiation levels in the fuel-handling. areas of the containment ishall.be monitored continuously.

c.oThe core'suberitical-neutron flux shall be continuously monitored by

) at-least-two neutron-monitors, each with continuous visual indication in the control room and one with audible indication in the containment, which are in service whenever core geometry is being changed. When core geometry is not. being changed, at least one1 neutron. flux monitor shall be in service.

d. The plant shall be - in' the REFUELING condition.

. .gy igi-i

TS.3.8 2 3.8.A. lie, During movement of fuel assemblies or control rods out of tho l reactor vessel, at leastR23 feet of water shall be maintained above the reactor vessel flange. The required water level shall be verified prior'to moving fuel assemblies or control rods and at least once every day while the cavity is flooded,

f. At least one residual heat removal pump shall be OPERABLE and running. The pump may be shut down for up to one hour to facilitate movement of fuel or core components.

g. If the water level above the top of the reactor vessel flange

-is less than 20 feet, except.for control rod unlatching / latching operations or upper internals removal / replacement, both residual heat removal loops shall-be OPERABLE. -

h. Direct communication between the control room and the operating floor of the containment-shall be available whenever CORE:

ALTERATIONS are taking place.

1. No: movement of-irradiated fuel in the reactor shall be made until the reactor has been suberitical for at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

' j. The radiation monitors which-initiate isolation of the Contain.

' ment Purge, System shall be tested and verified to be OPERABLE prior to CORE ALTERATIONS.

k.- The manipulator crane shall be OPERABLE for the movement of fuel assemblies.

2. .If any of the_above-conditions are not met, CORE ALTERATIONS shall cease. -Work shall be initiated to correct the violated conditions so that the specifications are met, and no operations which may increase '

the reactivity of the core shall be performed.

3. If' Specification 3.8.A.1,f or 3.8.A l.g cannot be satisfied, all fuel handling operations in containment shall be suspended, the

requirements of Specification 3.8.A.1.a shall be satisfied, and no reduction in reactor coolant boron concentration shall ins made..

TS.3.8 3 i

3.8.B. Laillandling Operations

1. During fuel handling operations in spent fuel pool area the l following conditions shall be satisfied.

a. Radiation levels in the spent fuel storage pool area shall be monitored continuously during fuel handling operations.

b. The spent fuel pool fuel handling crane shall be OPERABLE for the movement of fuel assemblies.

c. A rnininium boron concentration of 1800 ppm shall be maintained _

in the spent fuel pool whenever a spent fuel cask containing fuel is located in the spent fuel pool.

2. If any of the conditions in 3.8.B.1, above , cannot be toet, suspend all fuel handling operations in the spent fuel pool area and l initiate the actions necessary to re establish compliance with the requirements of 3.8.B.1.

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Tablo TS.4.1 2A (Page 1 of 2)

MINIMUM FREOUENCIES POR EOUIPMENT TESTS Test Frequency

.. Control Rod Assemblies Rod drop times All rods during each refueling l of full length shutdown or following each rods removal of the reactor vessel head; affected rods following maintenance on or modification to the control rod drive system which could affect performance of those specific rods __

2. Control Rod Assemblies Partial movement Every 2 weeks l of all rods

3. Pressurizer Safety Set point Per ASME Code, Section X1 Valves Inservice Testing Program 4, Main Steam Safety Set point Per ASME Code, Section X1 Valves inservice Testing Program

5. Reactor Cavity Water level Prior to moving fuel assemblies or control rods and at least once every day while the cavity is flooded. l

6. Pressurizer PORV Functional Q,arterly l Block Valves

7. Pressurizer PORVs Functional Every 18 months -

8. Deleted

9. Primary System Leakage Evaluate Daily

10. Deleted 11., Turbine stop valves, Functional See (1) governor valves, and intercept valves.

(Part of turbine overspeed protection.)

(1) Turbine stop valves. governor valves and intercept valves are to be tested at a frequency consistent with the methodology presented in WCAP-11525 "Probabilistic Evaluation of Reduction in Turbine Valve test Frequency", and in accordance with the established NRC acceptance criteria for the probability of a turbine missile ejection incident of 1.0x10'S per year. In no case shall the turbine valve test interval exceed one year.

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Table TS.4.1 2A (Page 2 of 2)

MINIMUM FREQUENCIES FOR EOUIPMENT TESTS T121 Freauency

12. Manipulator Crane Load test for Once during each refueling OPERABILITY of outage prior to the start limjt switches, of CORE ALTERATIONS.

interlocks and alarms

13. Spent ruel Pool Load test for Prior to fuel handling N Fuel Handling Crane OPERABILITY of operations if not tested in limit switches, the previous 3 months, interlocks and alarms

B.3.8*1 3.8 REWELING AND WEL HANDLING Bases The equipment and general procedures to be utilized during refueling are discussed in the USAR. Detailed instructions, the precautions specified above, and the design of the fuel handling equipment incorporating built in interlocks and safety features, provide assurance that no incident could secur during CORE ALTERATIONS that would result in a hazard to.public health and safety (Reference 1).

-The requirements for containment penetration closure ensure that a release of fission product radioactivity within containment due to a fuel handling accident will be restricted from escaping directly to-the environment. -

Closure restrictions sre only required for containment penetrations that-

. provide-direct-unfiltered access from containment atmosphere to outside atmosphere.

>There:are no closure restrictions during CORE ALTERATIONS on containment-

-penetrations that provide access-from-the containment atmosphere-into-areas protected by OPERABLE automatic safegu-*ds ventilation systems which actuate _ on.high radiation and filter all releases to the environment through particulate absolute charcoal filters. No closure restrictions are'necessary for those penetrations because any radiological releases to-those areas following a fuel handling accident in containment would be released to the environment via a particulate absoluto charcoal filtration system. The particulate absolute charcoal filtration of the fission-

. product radioactivity released during a design basis fuel handling accident in containment would maintain off site radiation exposures well within the requirements of 10 CFR Part 100. /

For penetrations to be open into the Shield Building Annulus during CORE ALTERATIONS, the: Shield Building Ventilation System shall be OPERABLE and -

for penetrations to be open into the Auxiliary Building Special Ventilation-Zone during CORE ALTERATIONS, - the Auxiliary Building Special Ventilation System shall be OPERABLE.

'Whenever changes are not being made in core geometry, one flux monitor is sufficient. This permits maintenance of the.instrumenta-tion. Continuous monitoring of radiation levels and neutron flux provides immediate indication of an unsafe condition. The residual heat removal pump is used to maintain a uniform boron concentration, t

Under' rodded and unrodded' conditions, the Kerr of the reactor must be '

less-than or equal to 0.95 and the boron concentration must be greater i than.or equal to 2000 ppm. Periodic _' checks of refueling water boron concentration insure that proper shutdown margin is' maintained.

'3.8.A,1.h allows the control room operator to inform the manipulator operator of any impending unsafe condition detected from the main

-control board indicators during fuel movement.

No movement of fuel in the reactor is permitted until the reactor has

.been'suberitical for at least 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to permit decay of the fission products in the fuel. The delay time is consistent with the

. fuel handling accident analysis (Reference 2),

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f6 'O i -a B.3.8 2 su 4 i e ,

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. 3;8 REFUELING ~AND FUEL HANDLING' r

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o Bases continued ,

. Fuel will not be -inserted into a spent fuel cask 'unless a minimum boron tconcentration of!1800 ppm ~is present. The 1800 ppm will' ensure that k rt- -

'for,the' spent _ fuel cask, including statistical uncertainties, will be less than~orie qual _to 0.95 for all postulated arrangements of fuel within the

--cask.

The number 1of recentlyLdischarged-assemblies in Pool No. I has been ,

limited.to 45 to'prc~ ie' assurance that in the event of loss'of_ pool JOgi cooling; capability, .- %t eight hours are avai;4Sle under worst case i.

@f , . , , conditions to makeirepurs until-the onset-of boiling.

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-j~( TherSpent Fuel Pool Special Ventilation System (Reference 3) is a

?q safeguards systemLwhich maintains _a' negative pressure in 'he spent' fuel

-enclosure upon detection of_high. area radiation. . The Spent Fuel Pool Normal Ventilation: System is automatically-isolated and exhaust air.is

. drawn through filter modules containing;a roughing filter, particulate filter--and a charcoal filter before discharge to the environment via one of the Shielf Building exhaust- stacks. Two completely redundant trains _are-provided. The: exhaust fan and filter of each train are shared with=the' corresponding train of the Containment In-service Purge System. .High efficiency-particulate-absolute (HEPA) filters are installed ,

before(the' charcoal adsorbers to prevent clogging of the' iodine adsorbers in-each SFPSVS. filter train. The charcoci adsorbers are' installed to reduce'the_ potential release of radioiodine to the environment. -

During movement.of irradiated fuel assemblies or control rods, a water level of 23 feetLis maintained-to provide sufficient shielding.

The1 water level-may be~1owered to the top of the RCCA drive shafts for latching and unlatching. 'Mae water level may also be lowered below 20 feet: for upper internals removal /rer'acement. _ The basis for these allowance (s)_are (1)Lthelrefueling cavity pool has sufficient level'to allow time to initiate repairs or emergency procedures to cool-the

. core, (2)-during latching / unlatching and upper internals removal / replace-ment the. level is closely monitored because the activity uses this level as a reference point, (3) the time spent at this level is minimal.

The requirements for the storage of low burnup fuel in the spent fuel pool ensure that the spent fuel pool will remain suberitical during fuel

-storage. -Fuel stored in the spent fuel pool will be limited to a maximum enrichment of 4.25_ weight 1 percent U-235. It has been shown by criticality analysis that the_ use of the three out of four storage configuration will assure' that the K.rt will remain less than 0.95, including uncertainties,

.when fuel with a maximum enrichment of 4.25 weight percent U-235 and average: assembly burnup of less than 5,000 MVD/MTU is stored in the spent fuel' pool.

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/*a B;3.843 In-

-3.8' REFUELING'AND FUEL HANDLING Bases continue'd. .

3 The requirement for maintaining the spent fuel pool boron concentration-greater-than 500 ppm whenever fuel with average assembly burnup of less-than 5,000 MWD /MTU-is stored lin the spent fuel pool ensures that Kerr for ,

the' spent' fuel poo1 ~ will: remain less .than 0.95, including uncertainties,.

eveh if a fuel assembly is inadvertently inserted in the empty cell of the lthree out of four t,torage. configuration.

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' References

1. USAR, Section 10.2.1.2

2. USAR, Section 14.5,1 1 3. USAR, Section 10,3.7-O k

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