B12504, Submits Addl Info Re 860521 Application to Amend License DPR-65,allowing Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per 870309 Request.Sys Description of Consolidation Process Encl

Submits Addl Info Re 860521 Application to Amend License DPR-65,allowing Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per 870309 Request.Sys Description of Consolidation Process Encl

ML20210C319
Person / Time
Site:	Millstone
Issue date:	04/30/1987
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
B12504, TAC-65274, NUDOCS 8705060156
Download: ML20210C319 (10)

Text

r- 1 o

o General Offices

• Selden Street, Berlin, Connecticut 9 a s*s exNm iuNw P.O. BOX 270

• * * * ' " * " " "" HARTFORD, CONNECTICUT 06141-0270 k k j 7d C'"C,"w",,",, (203) 665-5000 April 30,1987 Docket No. 50-336 B12504 Re: 10CFR50.36 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Storage of Consolidated Spent Fuel In May,1986,(I) Northeast Nuclear Energy Company (NNECO) submitted to the NRC Staff a request to amend its operating license, No. DPR-65, for Millstone Nuclear Power Station, Unit No. 2, to allow storage of consolidated spent fuel in the Unit No. 2 spent fuel storage pool. As a result of the NRC Staff review of this proposal, the NRC Staff forwarded to NNECO a Request for Additional Information (RAI).(2)

In a subsequent telephone conversation with the NRC Staff on March 17, 1987, the Staff stated that issuance of the requested license amendment would not be delayed pending resolution of this RAI and that the requested license amendment would be issued without proposed Technical Specification (TS) 3.9.19, which is addressed by the RAI. The Staff also stated that all other technical issues have been adequately addressed and that no further NNECO action is necessary for NRC issuance of the license amendment.

The purpose of this letter is to document our understanding of the status of the proposed license amendment and to provide the NRC Staff with the response to this RAI.

NRC Inquiry #1 Proposed TS 3.9.19 would require that candidate fuel assemblies (for consolidation) must have decayed for at ! cast 5 years. Please provide a Justification for the proposed decay time in terms of the consolidation process.

In this regard, you should provide a complete description of the consolidation process and an associated safety analysis.

(1) 3. F. Opeka !ctter to A. C. Thadani, dated May 21,1986, " Millstone Nuclear Power Station, Unit No. 2; Proposed Change to Technical Specifications, Storage of Consolidated Fuel."

(2) D. H. Jaffe letter to E. 3. Mroczka, dated March 9,1987, " Request for Additional Information, Millstone Unit No. 2, Spent Fuel Consolidation."

0705060156 870430 l PDR ADOCK 05000336 8 p PDR \

U.S'. Nuclear Regulatory Commission B12504/Page 2 April 30,1987

Response

The proposed TS 3.9.19 requiring that candidate spent fuel assemblies (for consolidation) have a 5-year decay time is not based on consolidation process considerations.

The May 21, 1986 submittal identifies that the thermal hydraulic design of the consolidated fuel storage box, as well as the design basis heat load for the spent fuel pool (with respect to 688 consolidated boxes), is based upon the 5-year decay criterion. (Refer to submittal pages 1-1, 1-5, 3-11 and Table 3.2-2).

This information is consistent with the March 30, 1984 submittal (3) to the NRC on NNECO's Spent Fuel Disposition Plans for Millstone Unit No. 2 and the May 17, 1984 Summary Meeting with the NRC in Bethesda, Maryland, as documented in the NRC Minutes, dated June 4, 1984.(4) Furthermore, the NRC Minutes identify that the 5-year decay criterion was specifically discussed as a conservative design basis for the storage of consolidated spent fuel.

Attached, for your information, is a copy of a system description on the consolidation process intended for use at Millstone Unit No. 2. Safety evaluations of this consolida:lon process are currently being conducted. NNECO intends to submit the results of these evaluations to the NRC Staff when complete.

NRC Inquiry #2 TS 5.6.3 provides for a total of 1346 storage locations in the spent fuel pool. The

, practical limit for fuel storage is 1277 locations due to the need to allow 5 years

for decay time of fuel assemblies prior to consolidation. The remaining 69 locations would contain cell blocking devices. You should propose a revised TS 5.6.3, limiting storage to 1277 locations, or justify the need for 1346 locations.

Response

The above referenced paragraph 5.6.3 is the Capacity description that appears in the DESIGN FEATURES portion of the Technical Specifications. The purpose of this description is to delineate the actual number of storage cells associated with i the spent fuel rack inventory in the pool. This description does not establish the spent fuel capacity of the pool which is determined by; (3) W. G. Counsit to 3. R. Miller, dated March 30,1934, " Millstone Nuclear Power Station, Unit No. 2 Spent Fuel Disposition Plans for Millstone Unit No. 2."

! (4) D. B. Osborne to Northeast Nuclear Energy Company, dated June 4,1984,

" Summary of Meeting with NNECO on Spent Fuel Disposition Plans for Millstone Unit No. 2."

~

- U.S. Nuclear Regulatory Commission B12504/Page 3 April 30,1987

1. A letter to the NRC Staff, dated May 21', 1986', which states the capacity as 1965 fuel assemblies.

2. Attachment 2 to the May 21, 1986 letter, which states on page 1-5, that the storage restrictions and thermal load restrictions imposed by the cooling system establish the maximum spent fuel capacity of 1965 to be distributed as:

10 spare cells 362 Intact fuel assemblies with less than 5-year decay 217 reserved for full core offload 688 cells containing consolidated fuel @ 2:1 (equivalent to 1376 intact fuel assemblies)

3. Attachment t to the May 21, 1986 letter, the proposed TS 3.9.20 establishes the storage configuration requirements surrounding the presence or absence of the cell blocking device in Figure 3.9-2 of the

, submittal.

If the cell blocking device is surrounded by consolidated fuel, it may be removed and a consolidated storage box placed in the cavity location.

However, the cell blocking device's primary function is to prevent inadvertent usage of the blocked location when the area is occupied by intact spent fuel assemblies.

Statement (2) above indicated that 362 intact assemblies with less than a 4

5-year decay comprised part of the total capacity. Specifically,157 Intact assemblies would reside in Region I and 205 intact assemb!!es would reside in Region II, requiring 69 blocked locations to support the criticality bases for the assemblies in Region II.

3 Therefore, in order for the total spent fuel pool capacity to support a total spent fuel assembly inventory of 1965, the total spent fuel rack capacity 3

must be 1346 (i.e., 1277 plus 69), as stated in DESIGN FEATURE i Section 5.6.3.

We trust you find the above information responsive to your request.

4 Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY 1

E. J.Tirg' cilla' ~ '

Senior 41ce Preside nt //

cc W. T. Russell, Region I Administrator D. H. Jaf fe, NRC Project Manager, Millstone Unit No. 2 T. Rebelowski, Resident inspector, Millstone Unit Nos. I and 2

Docket No. 50-336 B12504 Attachment 1 Fuel Consolidation Demonstration Program Description April,1937

Rheud 1

• Btwon

- FUEL CONSOLIDATION DEMONSTRATION PROGRAM SYSTEM DESCRIPTION Fuel assemblies to be consolidated, having a mini-mum of 85% burnup and 5 years' oubsequent residence A conaolidation concept has been developed which time in the pool, are deposited in the temporary storage permits the coordinated disassembly of spent fuel rack by the spent fuel handling machine. Consolidation essemblies and subsequent repackaging of the rods into takes place in the work station frame, which supports dense close packed arraye. For this program,the actual seven individual work stations. A traversing carriage in plant work will be perfcrmtaed in the Millstone II on the work station upper plate aligns fuel manipula.

spent fuel pool cask laydown area. Here, as shown in ting equipment accurately with theindividual stations.

Fig.1, the respective work stations, fuel support com- The fuel is dissembled in the first station by cutting ponents, hoisting equipment, filtration system, and off the upper end fitting and then removing fuel rods various handling tools, which comprise the consoli-singly or up to one row at a time by means of a multiple dation system, are insta!!ed. Also located within this rod pulling tool (MRPT). Rod pulling forces are main-general area is the main control console from which tained between preset limits. Fuel rods are then deposit-cperations are maintained and controlled. A temporary ed in an interim transfer canister (ITC) st the next work storage rack, which ie serviced by both the fuel hand- station.The ITC has channels which guide the rodsinto ling machine and the consolidation system hoist, holds a close packed triangular array at the bottom. Damaged intact and consolidation assemblies. fuel rods are deposited in the damaged fuel rod storage station after being separated form the row in the separ-p ation/ recovery station. The fuel rods in the ITC are normally traneferred by gravity into a consolidated fuel

]' storage box located in the next work station. Descent of

,,,,,, l the rods is controlled by a telescoping cylinder through All 6 the bottom of the box. A rod transfer tool can also be used to assist in this operation if required.The close J  ; packed triangular rod array resulta in a compaction ratio of 2:1. Ieckable covers are installed on the filled w ,g-

- consolidation fuel boxes before they are removed for

. .. , e a ,,,

?b ~ '- storage in the spent fuel pool.

Fuel assembly end fittings are placed in storage boxes e , at the end fitting storage station, for storage in the fuel l .p  ;

q=,vp,g,g,,,vgigo pool since they have high activity. Zircaloy gnd cages and control guide tubes have much lower activity and sainei=o eass ae'* are compacted by hydraulic cylinders in the compaction ews: sisa ssemet, station, for transportation to a radwaste disposal

'o stem hdty evat teams se i avion A filtration system is connected to the fuel disassem-stosaos s'a'io= bly, ITC, transfer and compactor work stations to

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,,,,,,,,,,1,, * "(',(' *( * ',

,, fN. . .*,*,j',jy;'" collect and filter out radioactive particulates generated j,';o," "" a hoa , . , , , c , , , , , ,,,, by operations performed at these stations.The MRPTis l

f NN s'a'io= enclosed by a shroud assembly which provides guid.

{e g I basemeationie:covse, ance and alignment, and vents released gases to the l

en'ea' ion l g j "'"*" plant gas handling system.

The consolidation system is controlled from a panel at 1 y temposae, stosas esca a work platform on the hoist assembly. Controllogic ia programmable to allow for changes as experience is gained. A TV system is provided for remote viewing of g

all consolidation operations. The overall process la Fig.1. Fuel Cohsolidation Equipment Layout. depicted in the Fig. 2 flow chart.

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BW504 ternal tubing cutter. The consolidation system require:

, j I the use of three variations of this cutter for MillstoneII

........e... fuel, because there are three possible diameters to con-e... s.. e.. e......a t : e v.

e..i s. v....... , s.d e.*... se..... e.' tend with in removing upper and lower end fittings.

... They are as follows-

• 1. Upper end fitting removal of an unsleeved fuel

[ ......a n c assembly.

***pa*'.*' v. v....e., s . ..

• ** = 6 8. 6...

2. Upper end fitting removal of a sleeved fuel assembiy.

y * - 4

3. Cutting within the necked <!own area of the guide i,..... ....

...... a.,....... tube for removal of the lower end fitting.

.....e.,..... , ' *-

, ' , , 'a The commercially available cutter tool bit angles

} ... 4 utilized in the guide tube cutter have been optimized to e.....e....... i .....a n c

"*"'" give reasonable cutter life with an improved cut, which I has no "curlycue" or loose fragment. while also pro-4 8apa's ce*** *ad viding good penetrating characteristics.

c .. i .. .. s. a e.a... - t.. o. c... s..

e... .e a.4 i,..... v.

o,.4 c . . . a . .. . si . i... s,..... e..i 4

i..... .... c... o a... e... c . . . . . ... ,,,,,,,,,,,,

e..i a w . . c .......

4

v. se... e..e e..i i

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a.pa * * =......,.i.44.....,.i..

t... s...... e...

Fig. 2. Process Flow Chart.

EQUIPMENT DESCRIPTION The following equipment has been designed and fabricated for use in the program.

Interim Transfer Canister (ITC)

The ITC, shown in Fig. 3, serves to guide the rods from a rectangular array into s triangular array.This is accomplished by providing each rod with a straight line path from top to bottom through an upper gridded sec-tion and a lower section of gradually occurring converg- ,

h ,[p' ing corrugations.  !

Attached to the bottom of the canisteris a gate mech-anism, which supports a transferable bottom during '

loading and while transporting fuel from the ITC station to the transfer station.The gate mechanism also alicws the transfer piston to pass through and accept the load of the fuel rods. Actuation of the gate mech-anism allows for the release of the floor for a controlled tran*fer of rods from the ITC into the consolidated canister. the floor then becorning the base of the con-

• ** **" # ##' Mulitple Rod Pulling Tool (MRPI')

The multiple rod pulling tool as shown in vig. 4 is Guide Tube Cutter A guide tube cutter is used to disassemble the fuel comprised of three sub assemblies: the pulling head, the assembly. The guide tube cutter is a single pass. in- shroud and. the mast.

Rhchmed 1 tuzso9 y unao e'= gauge the maximum allowable rod diameter. If a fuel

. O ive,' "neen cas casus rod has an excessive diameter or localized blister,it will

1. "3 W " not pass through the alignment bar. Rod slippage will

' occur and identify a possibly damaged rod.The align-a / *.'iIIM&M'."'""

ment bar is then partially retracted to allow the local.

ized deformation to pass by, s.nd then closed to continue alignment and gauging operations.

, , p,3

'i evw=o asas sneovo \ Fi Filter System I. The filter system consists of two pump and filter unita eutono miao N OW' running in parallel, manifolded to four work stations to

• '"'"'"" F'th"'

N provide positive downward flow in each station.The pump and filter units are sized to ensure sufficient

/u'c o OIle"Ei, Yi velocity at the MRPT and work station interface in l

k e ,[p. order to entrain and filter out released crud before it can i

disperse within the cask laydown area.

The filtering occurs in several stages to minimize

/) """IIs'iIio'A a '=i isvoimia W .' filter usage and therefore minimize the volume of waste v$

,vmI,N,'iaY[vneen 4

evaimo asao avios sae ,

'"'" products. A strainer at the pumpinlet protects the pump

'"" $ v,,,*',",',b . > es,uan sumo caesu,, from large chips.The filter also collects zirconium alloy

.,'), It chips which may be released in the consolidation effort, Downstream of the pump are two additional stages of

,,,n,,,,,,,, m *i* ty i

..,, r filtering.

ano.o.ime....

i=> eini m

insa (k*. Volume Reduction Systent/ Compactor

,,ve', o"',',', Q $

eun eco avo==ini sans -t . . ,,vn son The volume reduction system depicted in Fig. 5,is a F hydraulic powered compactor which systematically shears sections of the grid and grid guide tube assembly Fig. 4. Multiple Fuel Rod Pulling Tool. and compacts each section in three directions to form briquettes. The briquettes are then loaded into a waste box and further compacted to achieve a 10:1 compaction The shroud assembly sits on a X.Y positioning table ratio.

cnd can be located above any of four stations (i.e., fuel disa ssembly, ITC, separation. or da ms ged fuel rod).The mast and pulling head assemblies are supported on the '

hoist assembly, and are guided by their shroud during s their vertical travel.The pulling head is the mechanism that graples from one to fourteen fuel rods for removal 4 a/ [

from the fuel assembly.The grippers of the pulling head [

can be oriented to pull up to one row of fourteen rods. N Each gripper can be individually controlled from the 5 main console to either release a rod, or pull the rod with -

/ ii c maximum preset force.Preloaded springs provide fail. '

1. l

[

safe gripper closure and a detection system provides information to controllogic regarding rod penetration e .

,l ,

l into the grippers and rod slip. Detection of rod slippage G e

/g'9 immediately stops the hoist pull and informs the opera-O tor of which rod has slipped. \

The fully enclosed shroud is vented to the plant's gas handling system to capture any released gases. Remote- / [

ly Ietractable fuel rod alignment bars are located at the 4

, /\

k [

bottom of the shroud.The alignmentbars are retracted a N to allow the pulling head to exit the shroud and ...ple r/ f. (

the fuel rods. As soon as the pulling head is lifwd past .

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[Te l

them, the alignment bars, are closed to maintain precise fuel rod alignment for correct insertion into the ITC.

Fig. 5. Compactor,

.I These fuel rod abgnment bars are also designed to i

b 3

R b c. b e d 1.

. 0125cy Consolidated Fuel Storage Box Temporary Fuel Storage Rack The consolidated fuel storage box shown in Fig. 6,is The temporary fuel storage rack is a free-standing sized to accept the fuel rods from two fuel assemblies anembly, located within the cask laydown area, and is und to temporarily store 9 fuel assemblies in a Sm3 reconfigured into a tightly packed triangular array, The consolidated fuel storage box contains the floor array for batch processing.The spent fuel pool can then be isolated from the processing area by installation of which is transferred from the interim transfer canister to the fuel storage box.The floor design includes flow the cask laydown gate, thus minimizing crud'infil-holes to allow for cooling of the consolidated fuel tration and accidental contamination of the spent fuel assembly. A locking cover assembly is installed mto the pool during the fuel consolidation process.

upper portion of the consolidated fuel storage box to Hoist Assembly contain the fuel rods. The cover design permits grap-pling of the loaded storage box in a manner similar to The gantry styled hoist assembly,similarin design to grappling of the spent fuel assembly. Alocking tab, not the spent fuel handling machine, spans the cask lay-designed to be removable, provides for visual fuel down area, and the assembly is guided on parallel rails accountability.

installed at deck level.The track rails extend beyond the cask laydown area to permit " parking" of the hoist assembly in a remote area, allowin g the spent fuel hand-ling machine to maneuver within the cask laydown area. The hoist assembly has a 6,000 pound load capae-ity with a total vertical travel of 52 feet 22 feet of which " -

is above deck level. g j '

Control Console l

The main control console, located on the work plat- * *-

form of the hoist sesembly, houses a programmable f.

controller and the readouts and controls for the hoist -

i assembly, compactor system, multiple rod puller, filter l ,

system, X Y positioning table and TV system. This l

prorrammable controller monitors the entire fuel con- +  !

solidation process, and the controller interfaces the logic of the numerous controls to minimize operator error. In addition, the programmable controller facil-ities modification of the process logie as experience is j

gained. -

t' Lower Work Platform f y 1_

The main fuetion of the lower work platform is to support the individual stations listed below:

1. Fuel Disassembly Station I I I U I I

2. Interim Transfer Canister Station *

3. Damaged Fuel Rod Station

4. Separation /Hecovery Station

5. End Fitting Station Fig. 6. Consolidated Fuel Storage Box and Cover Assembly.

6. Fuel Rod Transfer Station

7. Compactor Station The lower work platform is supported by the cask lay-down area floor. Adjustable support pads are incor- METHODS DEVELOPMENT ANDTESTING potated into the lower work platform design for proper The fuel consolidation process resulta in rearrange-leveling and load distribution. The platform is located ment of fuel rods from a square or triangular pitch and and stabilized by brackets tied to pool wa!! embed. from a spaced to tight packed array. The analytical i

menta. methods used to satisfy safety and licensing require-

! TV Systerr. ments for seismic, criticality, and thermal hydraulic design analysis were modified to account for these A three camera TV system monitors all aspects of the changes.The following discussion highlights the work process. The monitors and a video recorder are located completed on this aspect of the program.

in the main control console on the work platform.

4, a- --

Abc.beM i

'~

iW2.5&f been completed on a full scale 19 rod triangular Storage Box Loading Configuration Testing pitch heated test section with rods in contact. Test The goal of this effort was to achive a 2:1 consolida. results indicate significant conservatism in an-tion ratio. Packing test with actual depleted UOs rods alytical methods for friction pressure drops and for having the dimensions of Millstone II fuel were per. these tight packed arrays the decay time prior to formed and a optimum storage box was designed.The consolidation may be reduced.

resulting metal to water ratio has been used for seismic, 3. Perform T H design analysis to demonstrate that criticality, and th'ermal hydraulic modeling and the consolidated spent fuel storage design meets analysis. the criteria that bulk boiling of the pool does not Seismic and Structural Testing occur and that maximum fuel clad temperature does not exceed 650*F during both normal oper.

The purpose of this work was to develop analytical f ation and accident conditions.This work has re-

' models and methods for seismic analysis of spent fuel sulted in a consolidated storage rack design which I

racks and storage pools. Full scale tests covering load meets the thermal hydraulic design criteria.

deflection, local stiffness and forced vibration of a loaded storage box have been performed to determine DESIGN AND ANALYSIS characteristics not easily determined by analytical means. Based on this work, model/ test correlation of In this phase of the program, the analytical methods natural frequency, damping and local box stiffness developed were utilized to complete detailed design and properties was performed. Further, a model for the fabrication of the consolidation hardware. Also, the storage box / fuel rack / fuel pool combination was de. developed analytical methods for seismic, criticality, veloped for use in nonlinear time history seismic and thermal hydraulics were used to design racks for storing consolidated fuel.

"""IY'8-Radiological Considerations Criticality It was concluded that fuel consolidation can be per-The purpose of this work was to revise the normal formed at Millstone II with the system developed in the light wster criticality analysis methods for higher rod program with minimal exposure to the plant operators.

density and triangular rod pitch. A calculational model In general, radiation levels due specifically to normal has been developed for use in design and licensing of consolidation operations are very low relative to the consolidated spent fuel racks and has been defined and spent fuel storage pool area radiation level. In the case vertified against existing critical experiments. This of consolidation equipment malfunction, the operator modelis based on a homogenized fuel module represen. dose is well within NU's administrative limits, which tation and 16 neutron energy groups which is suitable are themselves more stringent than 10CFR20 limits. It for design use in both KENO and DOT type analyses. was also concluded that, in the most severe accident The model yielded multiplication factors for critical ex. postulated during fuel consolidation, the dropping of a periments which are comparable to those obtained with loaded consolidation storage box, the site boundary 123 neutron energy group KENO calculations employ.

dose is well within 10CFR100 limits.

ing a more detailed spatial model.

Another aspect of this work is the evaluation of EPRI Spent Fuel Pool Cooling methods for reactivity monitoring and the testing The plant spent fuel cooling system capacity was l of a reactivity monitor for use in a hot consolidation found to be insufficent for the normal operation design demonstration at Millstone II. basis condition with the maximum quantity of spent

' fuel stored in the pool.The addition of a heat exchanger Thermal Hydraulics or technically specifying the allowable pool temper-The objectives of this work were to: ature was recommended. No change was necessary to

1. Develop analytical methods for use in evaluating conform to the abnormal operation (fuel core offload) consolidated spent fuel pool thermal hydraulics by design basis.

l1 It is recomended that the cask laydown pool water be I modifying appropriate existing T.H computer codes. VIPRE, GF14W, and CEPOOL were kept isolated from the spent fuel storage pool water by f examined and CEPOOL was selected for design means of the transfer gate during consolidation oper-analysis because it is a proven licensing tool,is ations to prevent contamination from s..tcring the more conservative and requires less computer time spent fuel pool. A submersible filtration unit should be available to clean up any accidental release of crud to than the others.

the cask laydown pool. Separate cooling should be

' 2. Perform heated flow tests to provide thermal hy-draulic data for triangular pitch flow channels to provided for the removal of heat generated in the cask laydown pool by fuel assemblies awaiting consolidation verify analyticalT.H methods. A test program has n

%e%eh 1

~

. ' Bia soy and while being consolidated. Circulation of cooling w:ter through a simpie pipe loop immersed in the pool world be adequate. The decay heat from candidate assemblies is low since they must have reached 85% of design burnup and have been discharged from the re-actor for at least five years.

9

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_ _ _ _ _ .