ML20127A087

Safety Evaluation for Design & Installation of New High Density Spent Fuel Racks

ML20127A087
Person / Time
Site:	Peach Bottom
Issue date:	07/31/1985
From:	PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20127A081	List: ML20127A075 ML20127A087 ML20127A091
References
NUDOCS 8508050395
Download: ML20127A087 (6)

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i PHILADELPHIA ELECTRIC COMPANY DOCKET NOS. 50-277 50-278 PEACH BOTTOM ATOMIC POWER STATION OPERATING LICENSES DPR-44 AND DPR-56 SAFETY EVALUATION FOR N

DESIGN AND INSTALLATION OF '

NEW HIGH DENSITY SPENT FUEL RACKS ,

DATED JULY 1985  !)

0 C500050395 B50001 DR ADOCK O 7

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PEACH BOTTOM ATOMIC PONER STATYON OPERATING LICENSES DPR-44 AND DPR-56 SAFETY EVALUATIO'N FOR DESIGN AND INSTALLATION OF NEW HIGH DENSITY SPENT FUEL RACKS DATED JULY 1985*

SUBJECT:

{ Modification 1140 involves the replacement of the existing aluninun high density spent fuel storage racks wl.th new stainless steel high density storage racks. The new rack structures will be able to withstand higher fuel loads and will increase the existing spent fuel storage capacity from 2,608 to 3,819 storage cells. This will delay .

the loss of full core discharge reserve from the 1987-88 time frame to .

1991-92. In addition to replacing the aluninun storage racks, the 1

,. spent fuel pool cooling piping and diffusers located in the spent fuel pool will be cut below the level of the racks and removed to provide additional space for storage racks. To avoid Interfereace with the new racks, some non-functional spent fuel pool floor swing bolts will be -

either cut-off or disassentaled at their hinge pins. ,

CONCLUSTONS: ,

The Peach Bottom spent fuel racks are classified as safety-related equipment.. The, mod.lf.lga} tion does not require changes to technical, specifications, involves no unreviewed safety question nor requires a license amendment. Section 5.Sc of the technical specifications, however, is Interpreted as requiring NRC review and approval of the new

• racks prior to' storing' fuel in them. This modification represents a -

change to the' plant,,ss described in the UFSAR. / .

i DISCUSSION:

The new spent fuel racks are being designed and fabricated by i Westinghouse Electric Corporation located in Pensacola, Florida. The new racks, designed to be freestanding, are Installed by setting them on the spent fuel pool floor as the old racks are removed. The insta'11ation and removal process of the new racks is very .stmilar to the last rarack job. The old racks are also freestandl.ng, and enpty racks *are removed by remotely attaching a 11ftIng tool and ralsIng them out of the pool. Current plans are to remove the old racks from the -

spent fuel pool, package them whole for off-site decontamination in accordance with DOT shipping requirements, and dispose of them as scrap aluninun. The off-site decontamination vendor will be chosen following bid review later in 1985.- If the fuel racks cannot be decontaminated  !

for free release, then the fuel racks will be disposed of at a low i j

level waste burial facility, 1 . ,

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) Just as with the last storage rack replacement at Peach Bottom, some

! of the pool floor swing bolts (no longer functional) will be removed to within one Inch of the fuel pool IIner to avoid Interference with

the support feet on the new racks. Also, to avoid rack feet Interference with the pool liner seam welds, leak detection trenches, sparger support brackets and support bases of removed swing bo)ts, some stainless steel plates will be set in place to span these Items and provide a surface for the rack feet to rest.

In order to provide additional floor space for new storage racks, the

and sections and diffusers of the spent fuel pool cooling discharge piping will be removed. The removal of the fuel pool cooling piping is supported by analytical calculations which shows that no effect on system operations will occur. The removed sections of pipe will be packaged for off-site shipment In accordance with DOT shipping -

requirements and disposed of with the old storage racks.

The work is expected to be accogilshed with existing and specially designed rack handling tools with possibly some diver support. New s racks and old racks will be moved so as not to pass over stored spent fuel. The new racks will be lifted and moved in accordance with the requirements of NUREG-0612. The old racks will be removed using the existing GCA/ PAR Systems lifting rig.

The modification has only minor physical I m act on plant systems and no performance Ig act. System operations such as; fuel storage, fuel handling, fuel preparations, spent fuel pool cooling, make-up water,

• water level monitoring, etc., will remain basically the same after the modification.

The design of the new storage racks is being performed in accordance with the Spent Fuel Storage Rack Technical Specification, SP-M-616, which invokes applicable NRC Regulations, Regulatory Guides, Standard Review Plan Sections, and Branch Technical Positions as'well as ,

appilcable ANSI /ANS' Standards, ASME Codes and Standards.

i The spent fuel pool structure was reanalyzed to verify that it is suitable for higher loads caused by increased spent fuel storage. The reanalysis was performed in accordance with applicable portions of MIC ,

Regulatory Guldes 1.12, 1.142, and Standard Review Plan 3.8.4. The pool structural reanalysis also uses ACI 318-83, ACI 349-80, and AISC Standards.

Analyses perfonned to evaluate the effect of the modification included the following:

• Spent Fuel Pool Structural Reanalysis i

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• Spent Fuel Pool Cooling System Capacity

• New Storage Rack Design j - Thenm1-Hydraulle

! - Criticality

- Structural /Selsmic o Radiological

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• Accident Evaluation 4

A discussion of the analytical methods and techniques for each of the above analyses Is contained in the attached Safety Analysis Report.

1 The results of the spent fuel pool structural reanalyses were used to specify the maxinun allowable spent fuel rack loads. The pool floor response characteristics were specified as input to the rack seismic analysis. The spent fuel pool cooling system analysis is performed to assess the Inpact of slightly increased heat loads due to increased storage of long decayed spent fuel.

The new storage rack design is confirmed by analysis to ensure that estab11shed design criteria is met. The rack thermal-hydraulic analysis is performed to show that the racks allow for sufficient natural circulation of pool water to remove decay heat and preclude local bolling under nonnat operations. A nuclear criticality analysis is performed to show that the fuel array remains subcritical (mder i normal conditions and postulated accidents so that the double *i contingency of ANSI /ANS 57.2 is met and that the effective neutron '

nuitlpitcation factor (k is less than or equal to 0.95 under all conditions. Structural N) seismic analyses are performed to ensure that the rack structure can withstand seismic, thermal, and fuel dead ~

and inpact loads. The racks are classified as SelsmIc Category I.

A radiological evaluation was performed to confirm that the design radiation zoning requirements are met for areas surrounding the spent .

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fuel pool, and to estimate reracking exposure. Fuel handling and cask hanaling accident evaluations were reviewed to determine that tha probability and consequence was not increased beyond that previously ,

. analyzed.

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10CFR50.59 CHANGES, TESTS, APO EXPERTMENTS:

1. Technical Speelfication Chances No changes to e,xisting Technical Specifications ard required as a result of this modification and no changes are proposed. The following appilcable Technical Specification sections have been reviewed and do not require revision: l

1) 3.10c -

2) 5.5c

2. Unreviewed Safety Question -  !

The rarack modification has been reviewed against PBAPS Technical -

Specifications, appropriate Regulatory Guides and Standard Review

• Plans and is deemed not to involve an unreviewed safety question. .'.i a) The probability of occurrence or the consequences of an .

accident or malfunction of equipment Inportant to safety ,

previously evaluated in the safety analysis report will not -

be increased by this modification. The storage racks are passive structures which are designed to maintain subcriti-cality and a coolable geonstry under all previously evaluated conditions. The larger storage capacity does not increase

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the radiological consequences of postulated accidents as these are controlled by freshly discharged spent fuel with L

- Its high natural radioactive decay. The new racks will not affect the amount or rate of spent fuel discharged from the reactor. The Installation of the new racks will be performed j using NRC NUREG-0612 so as to not affect the probability of a i malfunction of equipnent irrportant to safety. The new racks

are designed to maintain a k of less than 0.95. The nominal calculated k for Nmal storage is 0.9198. The maxinun calculated k,ff,ff under accident conditions Is 0.9357. -

The rack thennal-hydraulle analysis shows that up to 90% flow blockage can occur within a storage cell and there would still be no local or bulk bollfog inside of the cell.

Structural /selsmic analysis Indicates that the racks will be able to withstand all required loads and load conbinations as '

specified by Industry codes and regulatory requirements.

The results of spent fuel pool finite element structural reanalysis has confirmed that the pool can support the

• Increased fuel loads and meet all current code allowables.

The Ilmiting factor in the pool structure Is the transvorse i I

i shear capactty of the pool slab and the load transfer

capab!11ty of the wall / slab Joints. An upper bound analysis '

. based on the total shear capacity of the slab resulted in a

' 21.7% margin of safety conpared to the maxinun factored load.

A lower bound estimate of the margin of safety was calculated to be 0.5% above code requirements (which include code-P reqdired factors of safety). ..

The analysis of the existing spent fuel pool cooling capacity shows that tnder maxinun nonnel heat load conditions, bulk pool. water tencerature can be maintained below the design basis of 1.50*F with two out of three heat exchangers and

purps in service. The calculated maxinun tenperature inder thls condition Is 135'F. For maxInun abnonnal heat loads l (i.e. a full core discharge), three heat exchangers and punps are needed to msIntain tenperatures below 150*F. The maxinun tenperature under this condition is 18 3*F. If the required 6

1 nurber of puips and heat exchangers is not available, RtR can -

be tied into the pool cooling system.

l The proposed racks will not affect such parameters as fuel

! burn-up, amount of fuel used by the reactors, refueling

! schedule, or refueling operations. Experience has shown that solid and gaseous radioactive wastes are released to

! the pool envirorsnent as a roult of reactor pressure vessel head removal, and refueling. Within several weeks after j refueling, gaseous releases fran the pool diminish' to j insignificant levels, and corrosion particulate matter dislodged from the fuel due to fuel novament has been collected in the spent fuel pool clean-up system. The

generation of these low level radioactive wastes are not significantly affected by storage capacity. Operational l

experience at PBAPS has she m no noticeable increase  :

radioactive waste generation as a result of the last I increase in storage capacity.

5-Shielding calculations for the spent fuel pool, taking into I account the location and storage capacity of the proposed i racks, has confirmed that design radiation zoning requirements )

are met for areas surrounding the spent fuel pool. j b) The possibility of an accident or malfmetton of a different type than any evaluated previously in the safety analysis report is not created by this modification. The new storage racks being passive structures only Interact with the pool i floor and stored fuel in the same manner as the existing racks. The new racks do not introduce any new or different type of accidents or malfunctions. Existing fuel handling and cash handling accident evaluations are mchanged by the new racks. ,

c) The margin of safety as defined in the basis for the Technical Specifications is not reduced. The existing Technical does not Specification cite the maxinun on spent k fuel storagefor calculated maxinun the old k j$

It rage racks, ratherthemargin8hfsafety to criticality is the difference between the maxinun allowable (0.95) and a k o This margin of safety is not reduced by the new rINs.f 1.0. Adequate spent fuel pool water level is maintained as discussed in section 3.10c to provide sufficient shielding and cooling.

The new racks do not effect the pool water level and therefore, the margin of safety as derived is not affected by this nrsdification.

3. License Amendnent Based on the above discussions, an amendnent to the facility operating IIcense is not required, since this modification does not involve an unreviewed safety question nor is a change to ,the technical specification required, liowever, since technical specification 5.Sc has been interpreted as-requiring NRC review and approval of the new racks prior to ,

storing fuel, a Safety Analysis Report must be submitted. '

10CFR50.92SIGNIFICANTHAZARDDETERMhNATION Not required, no amendment to the facility operating Ilcense is required.

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