L-84-206, Forwards Addl Info Re Spent Fuel Storage Facility Expansion, Per NRC 840702 Request.Nitawl,Xsdrnpm & Keno-IV Used to Calculate Reactivity of Checkerboard & Configuration in Region 2

Forwards Addl Info Re Spent Fuel Storage Facility Expansion, Per NRC 840702 Request.Nitawl,Xsdrnpm & Keno-IV Used to Calculate Reactivity of Checkerboard & Configuration in Region 2

ML20094P234
Person / Time
Site:	Turkey Point
Issue date:	08/14/1984
From:	Williams J FLORIDA POWER & LIGHT CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
L-84-206, NUDOCS 8408170084
Download: ML20094P234 (7)

Text

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FLOHIDA POWEll & LIGHr COMPANY August 14,1984 L-84-206 Office of Nucicar Reactor Regulation Attention Mr. Steven A. Varga Chief Operating Reactor Branch #1 Division of Licensing i U.S. Nuclear Regttlatory Commission l Washington, D.C. 20555 l

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Dear Mr. Varga:

RE: TURKEY POINT UNITS 3 & 4 DOCKET NOS. 50-250 & 50-251

, PROPOSED AMENDMENT TO l SPENT FUEL STORACE FACILITY EXPANSION ADDITIONAL INFORMATION By letter dated July 2, 1984, the NRC requested that FPL provide additional information regarding criticality aspects of the proposed modification. The specific questions and responses are included as an attachment to this letter. As part of the response to Question No. 6 revised Technical Specification Pages 3.17-1 and B3.17-1 are submitted which delete all reference to U-235 lineer loading and use only weight percent U-235 as requested.

If additional information is needed, please contact us.

Very truly youre, fl &r

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Group Vf Nuclear Energy President JW/CJK/mp Attachment cci J.P. O'Reilly, Region 11 Harold F. Reis, Esquire 8408170084 840814 gcol PDR ADOCK 05000250 P PDR If FIOPt.E . , . $f HVING PLOPLF I

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ATTACHMENT PROPOSED AMENDMENT TO SPENT FUEL STORACE FACILITY EXPANSION REQUEST FOR ADDITIONAL INFORMATION Question 1 What is the nominal case kegg for Region I calculated by KENO and what t are the values of the biases and uncertainties referenced in Section 3.1.4.17

Response

The nominal case k,gt and uncertainties calculated by KENO aren k 0.9150 nominal B 0.0 delta-k method B .0025 delta-k part B 0.00740 delta-k mcch ks 0.00401 delta-k

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ks 0.013 delta-k method ks 0.00721 delta-k i mech '

Substituting these calculated values in the equation listed in Section 3.1.4.1 l results in the final k gg e for Region ! = 0.9403 Question 2 What computer codes were used to calculate the reactivity of the temporary checker board configuration in Region II. What is the nominal case k,g g and what are the values of the biases and uncertainties referenced in Section 3.1.4.2.27

Response

The computer codes used to calculate the reactivity of the checkerboard configuratiou in Region 2 were NiTAWL. XSDRNPH and Keno IV. These are the same codes and methods which were used for the Region I analysis. The nominal case k gr calculated in this case was 0.8342 with a 95/95 uncertainty level of 0.00468 Calculation of the remaining biases and uncertainties was not deemed necessary in this case since assuming conservative values for these terms will result in a final k gg e for the checkerboard configuration well below the required 0.95.

The acceptance criteria was determined to be met for this condition and no further detailed criticality analyses were performed.

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Question 3 What are the values of the biases and uncertainties referenced in Section 3.1.4.2.1 for Region 117

Response

The values of the nominal k,gg in biases and uncertainties aren k = 0.9020 nominal B . 0.0 delta-k method M = 0.0060 delta-k part B

• 0.00072 delta-k mech ks

• 0.00325 delta-k nominal ks = 0.013 delta-k method ks = 0.00890 delta k mech ks =

0.009 delta-k pu ,

ks =

0.0114 delta k bu Substitution of these values into the equation in Section 3.1.4.2.1 results in a final k ggo for Region 11 of 0.9304 Question 4 What constant value of rack k gg (including biases and uncertairties) do Technical Specification Table 3.17-1 and Spent Fuel Storage Facility Hodification and Safety Analysis Report Figure 3-3 represent?

Response

The constant value of rack k,gg including biases and uncertainties represented by Table 3.17 1 and Figure 3 3 is 0.9304.

Question 5 In those cases where fuel is to be placed in a checkerboard arrangement, we require the vacant spaces adjacent to the assembly being inserted to be physically blocked to prevent inadvertent assembly insertion. planne modify your design and procedures accordingly.

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i 1 n gesponse For normal spent fuel storage Fpt will not utilize the checkerboard storage configuration since sufficient Region I space is available for storage of fuel not meeting the burn-up requirements et Technical Specification Table 3.17-1, only during the reracking process, privr to placement of the new Region I racks, will it be necessary to store fuel in a checkerboard arrangement. By providing this type of storage the amount of fuel handling, radiation exposure and economic burden are reduced during the rcrack.

Fuel assembly placement will be under administrative control with verification that the adjacent cells are vacant. This control assures the proper placement of fuel assemblies when using the checkerboard storage configuration. Since the storage method is not for extended use, the concurrent misplacement of a fuel assembly and loss of soluble boron in the SFp is not considered credible.

In the unlikely event of a misplaced fuel assembly, criticality would be precluded by the boron concentration (1950 ppm) in the SFp. ,

The une of temporary blocking devices for this limited period of time is not l considered prudent since it would result in additional personnel exposure during  ;

l placement, removal and decontamination of the blocking devices. Additionally, '

l if decontamination is unsuccessful then these blocking devices would have to i be disposed of as radioactive material. On this bania, FpL does not feel the l use of blocking devices is justified.

Question 6 Since storage in Region !! is dependent upon initial enrichment as well as burnup, we requent that all references to the U 235 loading in the Technical Specifications be in terms of weight percent U 235 (enrichment) for consistency.

Response

References to the limiting linear loading of U 235 in the proposed Technical ,

Specification (3.17 Spent Fuel Storage) and its associated bases B3.17 are amended to reflect the limits in weight percent of U 235. These amendments are attached.

Question 7 l Most of the previously analysed pWR multi region burnup dependent spent fuct pools have operating procedures which require fuel to be stored initially in l the " safe" hurnup-independent region (Region !) be fore determining if storage in the burnup dependent region (Region !!) is appropriate. please comment on the advisability of this for Turkey point Hosponse The key parameter of interest relative to safe storage of spent fuel in l burnup dependent spent fuel pools is not the final assembly burnup at l End of Cycle, but whether the measured burnup value with appropriate uncertainties l is larger than the requirement for Region II. The intention for Turkey point is to compare measured burnups with uncertainties against requirements initially 60 days prior to planned shutdown. If the annemblion which will be discharged into the spent fuel pool meet the burnup requirement, loading of fuel directly into Region !! will be allowed. Independent verification of all data will be cecomplished prior to any fuel movement.

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Response (continued) '

In the event assemblies to be discharged do not meet the burnup requirement 60 days prior to planned shutdown, the measured burnups with uncertainties would again be compared to the burnup requirement 10 days prior to the planned shutdown.

This comparison will be the basis for determining storage acceptability. Again, independent verification of the comparisons between measurement with uncertainty and the burnup requirement will be completed prior to any fuel movements.

Eliminating the necessity for interim storage in Region I reduces the total

number of fuel shuffles and minimises personnel exposure. Under unusual t circumstances, e.g., an early outage, the fuel may have to be stored in the burnup-independent region for spe short period of time.

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c 3.17 ~ SPENT FUEL STORAGE Applicability: Applies to limitations on the storage of spent fuel assemblies.

Obiective: To minimize the possibility of exceeding the reactivity design limits for storage of spent fuel.

Specifications: (1) Fuel assemblies containing more than 3.5 weight percent of U-235 shall not be placed in the single region spent fuel storage racks.

After installation of the two-region high density spent fuel racks, the maximum enrichmentloading for fuel assemblies in the spent fuel racks is 4.5 weight percent of U-235.

(2) The minimum boron concentration while fuel is stored in the Spent Fuel Pit shall be 1950 ppm.

(3)* Storage in Region II of the Spent Fuel Pit shall be further restricted by burnup and enrichment limits specified in Table 3.17-1.

(4)* During the re-racking operation only, fuel that does not meet the

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burnup requirements for normal storage in Region II may be stored in Region II in a checkerboard arrangement (i.e., no fuel stored in adjacent spaces).

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• This Technical Specification is applicable only after installation of the new two-region

} high density spent fuel racks.

L 3.17-1

B3.17 BASES FOR LIMITING CONDITIONS FOR OPERATION, SPENT FUEL STORAGE

-1. The spent fuel storage racks provide safe subcritical storage of fuel assemblies by providing sufficient center-to-center spacing or a combination of spacing and poison to assure k eff si equal to or less than 0.95 for normal operations and postulated accidents.

2.* The spent fuel racks are divided into two regions. Region I racks have a 10.6 inch center-to-center spacing and the Region II racks have a 9.0 inch center-to-center spacing. Because of the larger center-to-center spacing and poison (BIO) concentration of Region I cells, the only restriction for placement of fuel is that the initial fuel assembly enrichment is equal to or less than 4.5 weight percent of U-235. The limiting value of U-235 enrichment is based upon the assumptions in the spent fuel safety analyses and assures . that the limiting criteria for criticality is not exceeded. Prior to placement in Region II cell locations, strict controls are employed to evaluate burnup of the spent fuel assembly. Upon determination that the fuel assembly meets the bumup requirements of Table 3.17-1, placement in a Region II cell is authorized. These positive controls assure the fuel enrichment limits assumed in the safety analyses will not be exceeded.

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• This Technical Specification is applicable upon c.stallation of the new two-region high density spent fuel racks.

B3.17-1.

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