A06896, Provides Response to Request for Addl Info Re Spent Fuel Consolidation,Per 881117 Telcon.Nrc Understanding Re Noninclusion of Temporary Storage Rack in Recent Tech Spec Change Request Confirmed

Provides Response to Request for Addl Info Re Spent Fuel Consolidation,Per 881117 Telcon.Nrc Understanding Re Noninclusion of Temporary Storage Rack in Recent Tech Spec Change Request Confirmed

ML20149D754
Person / Time
Site:	Millstone
Issue date:	01/04/1988
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
A06896, A6896, TAC-65274, NUDOCS 8801130113
Download: ML20149D754 (11)

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NORTHEAST UTILITIES cenerei offices e Selden S9eet. Berlin, Connecticut 9 '7eIZ5'u'[$I'E.Y[C

. P O. BOX 270

.a x .ct. *w cw- t AATFORD. CONNECTICUT 061410270 L L J Cl,d[$IES,((C'[, (203) 665 5000 January 4, 1988 Docket No. 50-336 A06896 Re: 10CFR50.59 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Soent Fuel Consolidation (TAC No. 65274)

On August 11, 1987,II) Northeast Nuclear Energy Company (NNECO) submitted a letter to the NRC Staff providing the esults of the 10CFR50.59 evaluation of the spent fuel consolidation process at Millstone Unit No. 2. As a result of the NRC Staff review of this submittal, the NRC taff forwarded to NNECO a request for additional information. In response to this request, NNECO and the NRC Staff engaged in a conference call on November 17, 1987 to discuss the request. The purpose of this letter is to provide the NRC Staff the requested information as discussed in the conference call. The requested information is provided as Attachment 1.

We trust you will find this information satisfactory and we remain available to answer any questions you may have.

Very truly yours, NORTHEAST NGCLEAR ENERGY COMPANY M &t E.M/ M'rodzka y Senior Vice President (1) Letter dated August 11, 1987, E. J. Mroczka to U.S. Nuclear Regulatory Commission, "Millstono Nuclear Power Station, Unit No. 2 Fuel Consolidation Program, Section 50.59 Evaluation of the Consolidation Process."

(2) Letter dated October 30, 1987, D. H. Jaffe to E. J. Mroczka, "Millstone Nuclear Power Station, Unit No. 2 Spent Fuel Consolidation Process (TAC No. 65274)."

8801130113 880104 I PDR ADOCK 05000336 008 p DCD 8h

U.S. Nuclear Regulatory Comm.ission A06896/Page 2 January 4, 1988 cc: W. T. Russell, Region I Administrator D. H. Jaffe, NRC Project Manager, Millstone Unit No. 2 W. J. Raymond, Senior Resident Inspector, Millstone Unit Nos. 1, 2, and 3 l

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Docket No. 50-336 A06896 Attachment 1 Response to Recuest for Additional Information i

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a January 1988

Attachment 1 Page 1 NRC Question #1 The evaluation of August 11, 1987 indicates that a 3 x 3 temporary storage rack vill be used for both intact and consolidated spent fuel.

It is the Staff's understanding that this rack vas not included in the Staff review of consolidated spent fuel storage authorized in the recent technical specification change approval. Provide justification for use of this rack to safely store consolidated spent fuel and indicate if such an action vill affect the existing technical specification. If so, propose the necessary technical specification change.

Response

The NRC Staff's understanding is correct with respect to the 3x3 temporary storage rack not being a part of the recent technical specification change for the storage of consolidated spent fuel at Hillstone Unit No. 2.

The 3 x 3 temporary storage rack is considered part of the consolidation system and equipment utilized to perform batch processing of spent fuel in the cask laydown area.

NNECO does not intend to take credit for the additional storage locations in the 3 x 3 temporary rack as part of the overall authorized limit still under review by the NRC Staff.

The 3 x 3 temporary storage rack vas analyzed by the same methods as the spent fuel racks in the spent . fuel pool for seismic / structural, criticality and thermal hydraulic considerations.

Additionally, the materials and fabrication of the 3x3 temporary storage rack conform to the requirements of a Quality Assurance Category 1, Seismic Category 1 structure. The 3 x 3 temporary rack is classified as an ANS Safety Class 3 component.

NRC Ouestion #2 According to the evaluation, the existing spent fuel pool platform crane vill be used for moving consolidated fuel storage boxes from the cask laydown area to the spent fuel pool. As the veight of a loaded i consolidated fuel box is greater than the design capacity of the crane, explain in detail how the crane vill be requalified for this heavy loads handling procedure.

Response

An evaluation was performed which addressed the use of the existing '

spent fuel platform crane for the purposes of moving the consolidated fuel storage boxes from the Hillstone Unit No. 2 Cask Laydown Area to the spent fuel pool. The spent fuel pool platform crane procurement, 1

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Attachment 1 Page 2 design, and testing documentation was revieved. It was determined that excess design margins of safety existed on the load bearing components of the crane which enabled the consolidated fuel storage boxes to be safely handled.

Each consolidated fuel storage box and the fuel handling tool has a submerged veight of approximately 2600 pounds. Prior to movement of the consolidated fuel storage boxes, a load test of the spent fuel platform crane vas performed. The load test veight was 125 percent of the 2600 pounds equaling 3250 pounds in accordance with ANSI B30.2-1983, "Overhead and Gantry Crane Requirements." The load test veight of 3250 pounds was suspended off the spent fuel platform crane and its load carrying capability was confirmed and verified by observing no loss of lift height during the test. A liquid penetrant test was performed on the crane hook and the crane was subjected to a visual inspection and operability test after the load test. All components vere found to be satisfactory.

NRC Ouestion #3 Provide more detailed information regarding the criticality sensitivity analysis performed to determine the minimum number of fuel rods that can be placed in the consolidated fuel storage box in order to Leet the rack K I limit of 0.95. Consider both cases with and without the blockingdeviceinstalledintheracklocations.

If for any reason the storage box cannot be loaded up to the minimum allowed content, indicate what actions you have considered to ensure that K,gg limited are maintained.

Response

On October 3, 1986, NNECO submitted a response to the NRC Staff question dealing with the reactivity effect of less than a full consolidated storage box (less than 352 rods). (Reference Docket

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No. 50-336, B12275, A05935.)

The response provided at that time stated that the consolidation process permits the placement of solid metal rods in positions where fuel rods are missing. For those instances where solid rods are not used, a limited number of fuel rods can be omitted based on the attached Figure 1. Using Figure 1, the reactivity effect of less than a full consolidated storage box can be established by determining the maximum number of fuel rods that can be omitted while maintaining K,gg at .95 or less.

NRC Ouestion #4 The seismic analyses consider the maximum tipping displacement of the '

1 temporary and other storage racks. Verify that the analysis for

Attachment 1 Page 3 partially loaded racks has considered the case .where all the cells along one' edge of the racks have been loaded with consolidated fuel boxes while the other cells are empty. Confirm that. unacceptable tipping of the rack vill not occur.

In addition, provide information regarding the exact locations of the ,

feet of the racks with respect to the outermost storage cells.

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Response

A seismic analysis has been performed that verifies that the maximum seismic tipping displacement of the 3 x 3 temporary storage rack under l nonsymmetric loading conditions is acceptable. Specifically, one of l the loading conditions considered was 3 consolidation storage boxes in  !

an outside rov vhile the other cells are empty. .For this case, tho  ;

factor of safety against overturning for the SSE was determined to be  ;

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The 3 x 3 temporary storage rack has a picture frame base velded to a  :

flat bottom plate. The 3 x 3 temporary' storage rack does not have any -j feet as is the case with the spent fuel racks that occupy the spent fuel pool, j i

In addition, a seismic analysis has been performed that verifies that the maximum seismic tipping displacement of the spent fuel paol storage .

racks when loaded with consolidated spent fuel in the "worst case" l scenario is acceptable. The details and specifics of this analysis was i provided to the NRC Staff in Section 4 of our submittal dated May 21,  ;

1986, "Storage of Consolidated Spent, Fuel." {

t NRC Ouestion #5 l t

Provide more detailed information to ensure that after pulling a rov of rods from a spent fuel assembly with the-multiple rod pulling tool  :

(MRPT) that no rod vill' slip or drop from the grip of the tool. .If,  !

for some reason (e.g., bent rod, svinging rods caused by forced cooling  !

flow in the work area, etc.), the rods in the MRPT cannot be deposited in the interim transfer canister (ITC) channels, indicate what actions

! vould be taken during the consolidation process. {

l It is the Staff's understanding from your evaluation that rods from one '

assembly will be deposited into the-ITC and then those rods vill be moved from the ITC to a consolidated fuel storage box. If so, provide more detailed information about the inner structure of the box which avoids ' movement or crossing of' rods within the box when the rods from the second fuel assembly are inserted in. the box. Describe the sequence of actions when loading the rods from the second assembly into

the box.

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Attachment 1 Page 4

Response

Retention of the rods in the grippers is maintained by spring forces that hold the grippers closed in the gripped position without other assistance. These gripping forces are set and tested during final MRPT assembly prior to starting consolidation activities. CE provided the results of this testing by letter MP2-87-039, dated February 26, 1987.

Further, the rod slip detection system alarms and automatically stops all motion (hojet, X-Y table, etc.), if for some reason a rod slip occurs.

The MRPT moves up and down within a shroud which acts to contain and guide the fuel rods at all times. The grippers of the MRPT hold the upper ends of the rods in the original fuel assembly pitch. The fuel rod alignment bars at the bottom of the MRPT shroud maintain alignment of the rods in the original fuel assembly pitch during pulling, transfer by the X-Y table to the Interim Transfer Canister (ITC) and subsequent lovering into the ITC. Since the alignment bars also act to gauge each rod for abnormalities including oversize diameter, assurance is provided that each rod withdrawn fully into the MRPT shroud vill fit into the ITC. If for some other reason the rods cannot be inserted into the ITC, up to one full row of fourteen rods can be moved to the recovery / separation station and deposited there for evaluation and/or recovery action. Unacceptable rods can be separated from good rods there and deposited in the damaged rod station for eventual disposition back to spent fuel pool storage or off-site shipment.

The ITC holds a full complement of 352 rods from tvo 14 x 14 fuel assemblies. All 332 rods are transferred at the same time to the consolidation storage canister. No storage canister inner structure is required with this design. A transferable floor in the bottom of the ITC holds the weight of the rods during the transfer and subsequently becomes the bottom of the consolidation canister.

NRC Question #6 In Section 1.2 of the evaluation, permanent changes to the plant resulting from the fuel consolidation program are identified. Explain in more detail the following.

(a) Repositioning of the brackets that support the level switch and temperature elements in the spent fuel pool.

(b) The meaning of "the north 'sveep' plates on the spent fuel pool fuel handling machine must be partially coped out."

Response

(a) The strap brackets that support the level switch and temperature elements for the spent fuel pool are located on the southeast c

Attachment 1 Page 5 intermediate vall elevation 38'6", between the cask laydown area and the = pent fuel pool.

The fuel consolidation hoist south rail / bearing plate is also-located on the intermediate vall elevation 38'6';.

In order to avoid interference with the rail / bearing plate, the excess material on the strsp brackets for the level switch and tuoperature elements vr e trimmed back at the ends. The modification did not diainish or alter the load' capacity of the bracket supports.

(b) The "sveep" plates are a non-structural part of the undercarriage axle assembly on the spent fuel platform crane. The "sveep" plates ensure removal of any inadvertent objects on the rail while the platform crane is in movement.

In order to install the consolidation hoist north rail / bearing plate on the 38' 67" elevation of the cask laydown area without interference, it was necessary to partially cope out the "sveep" plate at the edge of the section.

The "sveep" plate vill cont' ur to function as designed because the plate section directly above the platform crane rail was not affected by the modification. The modified section was at the edge of the "sveep" plate where the interference existed with the i north rail / bearing plate.

NRC Ouestion #7 In Section 7.2 of the evaluation, it is stated "fuel consolidation may be performed continuously...if the water temperature in the cask laydown area does not exceed 120*F." Provide information on the following.

(a) Hov was this temperature limit established?

(b) What is the temperature difference in cooling vater between the lover inlet and upper outlet of the consolidated box in the work area?

Response

(a) The temperature limit for the consolidation process in the cask laydown area was established by utilizing the maximum normal operating temperature of 120'F for the spent fuel pool, as defined in the Hillstone Unit No. 2 FSAR, Section 9.5.3.1.

(b) The temperature difference in cooling vater between the lover inlet and upper outlet of the consolidation storage canister in the work area is 18'F. The temporary storage rack is a3x 3

w Attachment 1 Page 6 array of vertical cells capcble of bolding intact consolidated fuel for batch processing during the concolidation operation. At the completion of a consolidation cycle, the rack can contain up to five consolidation canisters, each full of rods from two fuel assemblies. The coolant temperature rise determination in the conisters is based on a CEP00L computer case for storage modules with "mouse hole" coolant flov openings. The mouse holes are located at the bottom of each cell side vall to allov for coolant flow. The 18'F temperature rise is calculated for the center consolidation canister since for this case, the coolant must pass below the outermost canister in the rack to reach the center.

Additionally, it should be noted that on October 22, 1986, NNECO submitted a response to the NRC Staff question dealing with the results of the CEP00L calculations. (Reference Docket No. 50-336, B12297, A06007.)

NRC Question #8 Provide information concerning the visual or other inspections of the assembly to be consolidated in order to assure that no damaged rods vill be pulled from the assembly.

Response

On October 28, 1986, NNECO submitted a response to the NRC Staff question dealing with the method used for identifying fuel rods that are most likely to rupture. (Reference Docket 50-336, B12303, A06101.)

The response provided at that time stated that prior to consolidation, all candidate fuel assemblies vill be screened and preinspected with the consolidation system TV cameras to review the condition of the exterior rows of fuel rods. Any fuel rods / assemblies previously kiiovn to have defects or found to have defects vill not be consolidated.

Plant fuel history data vill be employed to identify known problems that may relate to existing rod defects.

NRC Ouestion #9 Provide information on the plans to test or demonstrate proper operation of the consolidation equipment and procedures in their actual configuration prior to beginning the consolidation of spent fuel.

Response

The consolidation system cold demonstration was conducted in December 1986 and the consolidation operating procedure qualification checkout was performed in February 1987, both with the system and equipment in their actual complete configuration. Additionally, prior to the Hot Demonstration, the on-site preaperational checkout of the system was

Attachment 1 Page 7 performed with the equipment in its installed configuration in the cask laydovn area at Hillstone Unit No. 2.

It should be noted that during the December 1986 Cold Demonstration, an NRC representative was present and issued an internal report (Project No. H-43) to Mr. L. C. Rouse on what was vitnessed during the test.

The NRC representative present at the test was Mr. James F. Schr aider, I Advanced Fuel and Spent Fuel Licensing Branch, Division of Fue' Cycle and Material Safety.

NRC Ouestion #10 After removing the upper end fitting and fuel rods from the spent fuel ,

assembly, provide information on how the end fittings, grid cages, and I control guide tubes are lifted to their respective work station.

Describe in more detail the compacting of the grid cages and control guide tubes including related operator exposure radiological considerations and how the compacted radioactive items vill be stored.

Response

The upper end fitting is cet free of the grid cage / guide tube assembly '

at the beginning of the process. It is then transported to a storage canister by a pneumatic operated lifting tool whic's attaches to the center guide tube ID by means of an expanding collet. At the end of the process, the lover end fitting is similarly cut free from the grid cage / guide tube assembly and transported to the storage canister with a pneumatic collet tool. The grid . cage / guide tube assembly is alse gripped by the center guide tube ID vith a pneumatic collet tool and transported to the compactor infeed chute for compacting or may be returned to the temporary storage rack.

A hydraulic povered compactor systematically shears sections of the grid cage / guide tube assembly and compacts each section in three directions to form briquettes. The briquettes are then placed into a storage canister for storage in the 3 x 3 temporary storage rack prior to being moved in the spent fuel pool for storage in the spent fuel racks.

During the fuel consolidation operations at Hillstone Unit No. 2, no significant change to the dose rates in the spent fuel pool area were I experienced. Exposure levels of the consolidation operators and  ;

utility personnel were consistent with routine fuel handling, repair, i and inspection operations of fuel assemblies. ]

NRC Question #11 Concerning the filtration system, provide more detailed information on how the system is designed to avoid the dispersion of fuel pellets and l

Attachment 1 Page 8 other "heavy" debris in the pool area should any rods break during the consolidation process.

Response

The present description of the filtration system is in Section 2.1.3 of the 10CFR50.59 Safety Evaluation submitted to the NRC dated August 11, 1987 (Docket No. 50-336, B12563).

It should be noted that each of the four vorkstations are fully shrouded such that any releases are contained and directly accessed by the filtration system.

NRC Question #12 The process and equipment descriptions included in your evaluation appear to indicate that the planned rod consolidation involves new technology. Provide references to earlier consolidation tests or experience which support a conclusion of proven technology.

Response

At the present time, fuel rod consolidation is a proven technology that has been vell demonstrated in the nuclear industry as a safe controlled operation.

The engineering and tooling designs associated with the systematic handling of fuel rods are deeply r.ooted in the fuel reconstitution experiences that have been a proven technology for over ten years.

Since 1982, the following fuel consolidation demonstrations have all been successful in establishing that spent nuclear fuel can be consolidated safely.

Oconee/Vestinghouse Ginna/U.S. Tool & Die Surry/EG&G Idaho Millstone / Combustion Engineering Prairie Island /Vestinghouse Although the safe operation has been vell demonstrated to date, rod consolidation is an evolving technology that vill require more focus and attention in the future to improving and enhancing the time motion, efficiency, and reliability of the system.

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