ML20059G941
| ML20059G941 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 11/03/1993 |
| From: | Hebert J Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| JRH-93-225, MN-93-97, NUDOCS 9311090198 | |
| Download: ML20059G941 (8) | |
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MaineYankee
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5EllABLE ELECTRICITY SINCE 1972 EDISON DRIVE + AUGUSTA, MAINE 04330 = (207) 622-4868 November 3, 1993 MN-93-97 JRH-93-225 UNITED STATES NUCLEAR REGULATORY COMMISSION Attention: Document Control Desk Washington, DC 20555
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) Letter, MYAPCo to USNRC, " Proposed Technical Change No.177:
Maine Yankee Spent Fuel Pool Reracking", MN-93-09, dated January 25, 1993.
(c) Letter, USNRC to MYAPCo, " Request for Addit ' anal Information--
Maine Yankee Proposed Amendment to Re 'ck Spent Fuel Storage Pool", dated October 7,1993.
i
Subject:
Response to USNRC Request for Additional Information: Proposed Change No.
177 (Spent Fuel Pool Reracking).
Gentlemen:
Attached, please find the Maine Yankee response to the above referenced USNRC questions (Reference (c)), relating to the USNRC review of the proposed Maine Yankee spent fuel pool reracking (Reference (b)).
We trust that these responses are satisfactory. Please contact me should you have additional qcestions.
Very truly yours,
% 'Q.
ames R. Hebei t, Manager Licensing & Engineering Support Department Attachment c:
Mr. Thomas T. Martin Mr. J. T. Yerokun Mr. E. H. Trottier Mr. Patrick J. Dostie Mr. Thomas R. Dignan, Esq.
Mr. Paul Stern, Esq.
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ATTACHMENT Maine Yankee Response to NRC Questions Concerning the Proposed Spent Fuel Pool Reracking
References:
(1)
Letter, Maine Yankee to USNRC, " Proposed Technical Specification Change No.177: Maine Yankee Spent Fuel Pool Reracking", MN 09, dated January 25, 1993 (2)
" Request for Additional Information - Maine Yankee Proposed Amendment to Rerack Spent Fuel Storage Pool", dated October 7,1993 NRC Ouestion la:
What loads can the following components of the hoisting system lift before any component part reaches its ultimate stress?
- i. Fuel building overhead crane ii. Temporary gantry crane (including motorized bridge and trolley) iii. Lifting rig (including load-to-yield stress) iv. Horizontal lifting slings Maine Yankee Response:
- i. Fuel Buildina Overhead Crane. The fuel building overhead crane, CR-3, has a 125 ton main hoist with a 25% design overload capacity, and a 20 ton auxiliary hoist. The auxiliary hoist will not be used for safety related lifts during the reracking process. CR-3 is classified as a Class IA crane in accordance with the specification CMAA-70. The maximum critical load for this crane is a spent fuel shipping cask at approximately 100 tons.
A safety factor of 4 at the 125% over rated capacity has been applied to the design. 'she crane has been load tested twice since installation in an "as installed" configuration at 156 tons. All loads associated with the reracking will be significantly less than design capacity of the CR-3.
ii. Terrorary Gantry Crane.
The temporary gantry crane, cor.aisting of the following components, caa lift the indicated load before any component part reaches the ultimate stress:
Load Lifted Before Crane Part Ultimate Stress is Reached Bridge & End Trucks 80 Tons Trolley 80 Tons Gantry Legs
- 80 Tons Hoist Unit **
100 Tons Short gantry legs are used as necessary to maintain bridge, trolley and hoist unit clearance above the top curb of the spent fuel pool (SFP).
The capability of the hoist unit exceeds that of other crane parts to meet the criteria of NUREG 0554. Please note that overload protection dc. vices are provided to prevent lifting any load that would approach the yield strength of a crane part.
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- iii. Liftina Rio. The vertical rack lifting rig assembly is capable of lifting 150 tons before exceeding the ultimate strength and 90 tons before exceeding the yield strength of any component part.
iv. Horizontal Liftina Rio. The horizontal rack lifting rig, which is not used in the fuel building, is capable = of lifting 45 tons before exceeding the yield strength of any component.
NRC Ouestion Ib:
What prevents parts of the temporary g;ntry crane (the gantry, the motorized bridge or trolley), together with the heavy load being lifted, from falling into the spent fuel pool or damaging dual trains of safe shutdown systems should a seismic event occur?
Maine Yankee Response:
Bridge and trolley rail hold-downs and double-flanged wheels will prevent the gantry crane system from leaving the rails during a seismic event. Proper seizing of hooks via safety catches will prevent the slipping of loads. The gantry crane system does not travel over any safe shutdown system components and it will be stored, when not in use, in a position where failure could not damage any train of a safe shutdown system.
NRC Ouestion Ic:
What are the specific standards (e.g., CMAA-70, NUREG-0554) to which the temporary gantry crane, and motorized bridge and trolley are designed?
Maine Yankee Response:
The temporary gantry crane, consisting of the following parts, is designed to the indicated standards:
Crane Part Desian Standards Bridge & End Trucks NUREG-0554, ASME N0G-1, CMAA-70, ASME B30.2 Trolley NUREG-0554, ASME N0G-1, CMAA-70, ASME B30.2 Gantry Legs
- NUREG-0554, ASME N0G-1, CMAA-70, ASME B30.2 Hoist Unit **
NUREG-0554, ANSI-N14.6, CMAA-70, ASME B30.2 Short gantry legs are used as necessary to maintain bridge, trolley and hoist unit clearances above the top curb of the SFP.
The hoist unit is designed to ANSI-N14.6 since it is also qualified for use as a critical load handling lift Ng device in accordance with NUREG-0612.
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- NRC Ouestion Id:
How will load shifting be avoided, in the event of the failure of one leg of the lifting rig?
Maine Yankee ResDonse:
The single-failure proof design of both the vertical lift rig and the gantry crane's hoist unit incorporates dual, coincident load paths. If any one of the four legs of the dual beam, cruciform lift rig fail, no load shift would be experienced due to coincidence in the designed load bearing scheme.
Likewise, the temporary gantry crane's hoisting unit incorporates a dual reeved lower block assembly which is reeved specifically to preclude a load shift in the event of a failure of one of the two load path.
NRC Ouestion le:
What is meant by " Free-path test each fuel storage location for acceptability?" (LR Page 9-2)
Maine Yankee ResDonse:
Free-path testing is that procedure whereby the full length drag test module (see Figure 9-5 of the Licensing Report) is inserted into each storage location, after each rack is installed in the SFP, as final verification of its acceptability for storing fuel subsequent to the handling involved during installation.
1 NRC Ouestion If:
What is the anticipated minimum separation distance between fua stored in spent fuel storage racks and empty racks being moved in and out of the fuel pool during the reracking process?
Maine Yankee ResDonse:
The anticipated minimum separation between fuel stored in the racks and empty racks, transmitting via safe load path during removal, is approximately 1 inch, the design clearance of the existing racks.
(Please note safe load path requirements in the response to question lh).
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NRC Ouestion lo:
When no.t in use, what will be the location of the temporary gantry crane, relative to the fuel pool and dual trains of safe shutdown systems?
Maine Yankee Response:
The governing philosophy, with regard to heavy lift operations, is that all loads, handling gear and lifting equipment shall be placed in their safest configuration when not actually involved in a lift operation.
The safest configuration for the temporary gantry crane is locating it north of and away from the SFP, on the fuel handling machine rail extensions, planned and installed for this very purpose. At no time, in operation or storage, will the temporary gantry crane be in a position where its failure would endanger a safe shutdown system.
NRC Ouestion Ih:
How does the safe load path minimize the potential for a dropped load to damage spent fuel?
Maine Yankee Response:
The " safe load path", by its applied definition, reduces the risk of load handling failure precipitated damage.
Maine Yankee's safe load path has the following attributes:
1.
No lifts over other racks with spent fuel stored in them.
2.
Maximum lift of 12 inches above the SFP floor during rack transit.
3.
Maximum transit speed of 6 feet per minute.
4.
Maximum lift speed of 6 feet per minute.
5.
Minimum distance between racks during movement (other than installation precision placement) will be 1 inch.
With these restrictions applying to all heavy load movement over the SFP, Maine Yankee has minimized the potential for spent fuel damage from a dropped load.
NRC Ouestion li:
How will the bridge rails be staged to clear a path for an existing spent fuel storage rack?
Maine Yankee Response:
During this sequence, the hoist unit is operating as an ANSI N-14.6 lifting device with the fuel building / yard crane supporting it.
Each bridge rail is both self supporting and independently powered, such that after the hoist / trolley unit has been lifted clear of the bridges and both inter-bridge connectors have been unpinned, the bridge rails can be driven apart to provide a clear path for rack passage. The north bridge rail unit has the capability to be electrically reversed via a supervisory controlled key-lock selector switch.
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NRC Ouestion lj.
In the. data table presented on LR page 9-6, what is meant by " Capacity: 20 tons NUREG-0612 useable; ANSI 14.6, 60 ton test" for the temporary gantry crane, and
" Rated Capacity: 20 tons NUREG-0612; ANSI 14.6, 60 ton test" for the bridge and trolley?
Maine Yankee Response:
The hoist unit is rated for a maximum single-failure proof load of 20 tons, all in accordance with the criteria of NUREGs-0612 and 0554.
The hoist unit is however, also used as a 20 ton critical load lifting device per the criteria of MUREG-0612 and ANSI-N14.6.
Specifically, as a critical load lifting device, ANSI-N14.6 requires that the lifting device be tested to 3 times the anticipated load to be lifted, or 60 tons.
The bridge and trolley are both design rated for a maximum 20 ton load in accordance with the criteria of NUREGs-0612 and 0554.
Specifically, for verification of wheel loads and seismic loads, the specific maximum critical load (MCL) for Maine Yankee will be less than the above 20 ton design load capability.
This MCL will be the actual maximum load to be lifted based on the weight of the heaviest rack (old and new) with all lifting fixtures attached.
NRC Ouestion 2a:
Table 5.1 of the LR gives 134 degrees Fahrenheit as the maximum spent fuel pool bulk temperature (at inlet to spent fuel heat exchanger) with a normal discharge of spent fuel.
Page 9-55 of the Maine Yankee Final Safety Analysis Report states that the fuel pool cooling system is designed to remove decay heat generated by one-third of an irradiated core and maintain a maximum fuel pool temperature of 100 degrees Fahreaneit. What is the reason for this difference?
Maine Yankee Response:
The 100*F stated in the FSAR was based on spent fuel pool original design conditions and cri. aria which were established during the design phase of the spent fuel pool cooling system. The 134*F contained in the licensing report explicitly considers the higher heat load due to:
Conservatively assuming that the (1/3) core discharge is completed in six (6) rather than 20 days assumed in the FSAR.
The increase in capacity of the pool to 2,019 cell locations.
The uprated plant power level.
The Maine Yankee FSAR will be revised to reflect these conditions according to the regular cyclic FSAR updating schedule.
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NRC Ouestien 2t:
How many locations in the spent fuel pool contain consolidated fuel elements? What is the expected number of consolidated fuel elements when operating cycle 23 has been c6mpleted (final core offload), and has this been considered in the decay heat calculation?
Maine Yankee Response:
Currently, only 2 consolidated assemblies have been Essembled by Maine Yankee. Maine Yankee has no plans to create any further consoliaated assemblies.
Additionally, Maine Yankee is limited by the requirements of Technical Specification 1.2 to the storage of 20 fuel assemblies in consolidated form.
Regardless of the number of consolidated assemblies, the use of the cyclic dependant fuel offload rate schedule explicitly addresses the actual number of assemblies in the SFP and restricts the offload rate such that the design heat load of 22.0 MBTU/hr is not exceeded. This approach, along with the proposed requirement that fuel cannot be consolidated until it has decayed for a.ninimum of 730 days, makes the heat load calculated independent of the assumption of the number and locations of consolidated assemblies.
NRC Ouestion 2c:
What is the anticipated operation of the spent fuel cooling system during and between refueling?
Maine Yankee Response:
The spent fuel pool cooling system is operated on the basis of maintaining a constant temperature range in the spent fuel pool at all times. During periods of refueling with freshly discharged fuel placed in the pool, the component cooling flow thrnugh the spent fuel pool heat exchanger may be increased to accommodate the increased heat load in the pool. Likewise, at the end of an operating cycle, with a low heat load in the pool, the requirement for a higher heat transfer will decrease, thus allowing for a reduction in the component cooling flow rate. As a general rule, however, Maine Yankee attempts to maintain the temperature at the fuel pool recirculation inlet to the spent fuel pool heat exchanger between the limits of 85 to 115 degrees Fahrenheit.
NRC Ouestion 2d:
At what temperature does the deionizer resin start to deteriorate? How is the resin protected from abnormally high spent fuel pool cooling water temperatures?
Maine Yankee Response:
The deionizer resin manufacturer recommends that fluid temperatures above 140 degrees Fahrenheit not be allowed to contact the resin beads. Maine Yankee assumes that at this temperature, the beads will start to deteriorate.
Maine Yankee protects the spent fuel pool deionizer by administratively controlling the fluid temperature to less than 135 degrees Fahrenheit. At temperatures approaching this value, the purification slip stream is either pre-cooled by routing it through the fuel pool cooler or bypassed entirely. Either option is suitable to ensure that no damage to the resin beads occurs. The temperature controls may be found in the Maine Yankee procedure 1-17-1, Fuel Pool Make-up, Cooling, &
Purification.
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NRC Ouestion 2e:
Which (if any) of the four alternate methods of cooling the spent fuel pool discussed in the tR can function on loss of offsite power 7 Maine Yankee Response:
Four alternate methods of cooling the SFP, in the event of loss of normal cooling, are discussed in section 5.4.3 of the licensing report. Three methods provide makeup water, either from the CVCS, from the fire main, or from primary grade water hoses.
One method supplies shell side cooling by t.Se plant fire protection system on loss of component cooling water.
A list of four alternate cooling methods for the SFP and their availability following a loss of offsite power (LOOP) is provided below:
AVAILABLE l
COOLING METHOD AFTER LOOP COMMENTS CVCS - Makeup Yes Primary water transfer pumps (P-24A and P-248) needed to supply makeup can be manually loaded on to the diesels by procedure A0P 2-46.
Fire Main - Makeup Yes Makeup from the fire main would be available I
from two separately powered fire pumps.
Fire pump P-4 is electrically powered from the diesel generator.
Fire pump P-5 is driven directly by a diesel engine.
Primary Grade Water Yes Primary eater transfer pumps (P-24A and Hoses - Makeup P-24B) :iaded to supply makeup can be manually loaded on to the diesels by procedure (AOP 2-46).
Heat Exchanger Yes Heat exchanger shell side cooling would also Alternate Cooling be available from the two separately powered fire pumps using the emergency cooling connections described in the FSAR.
This connection is proceduralized (OP l-17-1).
Both SFP circulating pumps (P-17A and P-17B) are automatically loaded on to the diesels.
It should be noted that, following a loss of offsite power, the SFP circulating pumps (P-17A and P-17B) and primary cooling (PCC) will automatically be loaded on to the diesels. Thus, the normal cooling flow path would not be interrupted as a result of a loss of offsite power.
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