ML20058L243
| ML20058L243 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 12/09/1993 |
| From: | Hebert J Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| JRH-93-253, MN-93-113, NUDOCS 9312160208 | |
| Download: ML20058L243 (15) | |
Text
_
MaineYankee R EE((B[E3QMRIClh[M5_C(1912
~
EDISON DRIVE
- AUGUSTA, MAINE 04330 + (207) 622 4868 i
December 9, 1993 MN-93-ll3 JRH-93-253 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 Specification Change No. 177: Maine Yankee Spent Fuel Pool Reracking", MN-93--
09, dated January 25, 1993.
(c)
Letter, MYAPCo to USNRC,
" Response to USNRC Request for Additional Information: Proposed Change No. 177", MN-93-97, dated November 3, 1993.
(d)
Letter, MYAPCo to USNRC,
" Response to USNRC Request.for Additional Information: Proposed Change No. 177", MN-93-106, dated November 23, 1993.
Subject:
Clarification of Responses to Reracking Questions Gentlemen:
I Attached, please find the Maine Yankee responses to the USNRC verbal requests for clarification regarding several answers to the USNRC questions on the proposed Maine Yankee reracking, Reference (b). The Maine Yankee responses to the written i
USNRC questions may be found in References (c) and (d).
The attachment to this letter contains the clarifications to the final remaining i
questions received to date from the USNRC on this subject.
We trust that these clarifications are satisfactory. Please contact me should You have additional questions.
Very truly yours, 1400.11
% Q.s@&#
mes R. Hebert, Manager Licensing & Engineering Support Department RPJ' f
Attachment P
c: Mr. Thomas T. Martin Mr. E. H. Trottier i
Mr. J. T. Yerokun l
Mr. P. J. Dostie l
Mr. Thomas R. Dignan, Esq.
Mr. Paul Stern, Esq.
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9312160208 931209 e
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PDR ADOCK 05000309 b
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ATTACHMENT From Reference (c):
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 Naine Yankee Clarification:
ii. Temporary Gantry Crane i
The Temporary Gantry Crane (TGC) functions in two roles at differing times during the reracking process; a) as an independent hoisting unit with access to all areas of the SFP; and b) as a lifting device between the load (e.g. new or old rack with lifting rig) and the 120 ton yard crane, which accesses only the cask pit.
During the installation or removal of racks, the TGC is required to function in both of the above roles.
For example, in removing an old rack, the TGC acts independently from the yard crane and via the bridge and trolley system accesses the old rack and moves it to the cask pit.
Then, the 120 ton yard crane attaches to and takes the load of the TGC hoist unit with the rack attached. The twin bridge beams are unpinned and driven apart to allow the 120 ton yard crane to lift the rack, suspended from the TGC hoist, out of the SFP. In the latter applications, the hoist unit's role is that of a lifting device.
Each role has its specific design criteria as noted below in the response to question 1.c.
The temporary gantry crane, consisting of the following principal components, can lift the indicated load before any component part reaches the ultimate stress:
Maximum Load Lifted Before Crane Part Ultimate Stress is Reached Bridge (Double Beam) 80 Tons End Trucks (each 2 per beam) 80 Tons (per beam)
Trolley 80 Tons Gantry Legs * (each 2 per beam) 80 Tons (per beam)
Hoist Unit **
200 Tons Short gantry legs are used to maintain bridge, trolley and hoist unit clearance above the top curb of the spent fuel pool and other interferences.
The capability of the single failure proof hoist unit exceeds that of other crane parts to meet the criteria of NUREG 0554 and ANSI N-14.6.
Please note that overload protection is provided to prevent lifting any load that would approach the yield strength of a crane part.
L:\\93mn\\93113 1
t From Reference (d):
1.
NRC Ouestion 1:
In constructing the acceleration and the displacement time histories from the l
ground response spectra, demonstrate that the time history of the acceleration bound the design ground response spectra. Provide the maximum ground response velocitires in three orthogonal directions at SFP slab level.
Maine Yankee Clarification:
The fuel pool DBE seismic displacements used for the analysis of the high density spent fuel racks are enclosed for use by the NRC, as verbally requested.
The fuel pool DBE seismic displacements are provided as three files on the PC compatible disk sent directly to the Maine Yankee Project Manager, Mr. E. H.
i Trottier. These files are:
DISPX East-West Displacement DISPY Vertical Displacement DISPZ North-South Displacement In further response to the NRC request, data sets for velocity and acceleration are also provided.
Please note that the original occeleration profiles are stored on a magnetic tape which has been subsequently archived since its use at the start of the reracking project and cannot be retrieved quickly from storage.
Thus, the velocity and displacement files have been developed by differentiation of the above displacement files. Since the differentiation of tabulated data leads to a loss of precision, the velocity data is less accurate than the displacement data and the acceleration data, which is obtained by double differention, is even less accurate.
Although not suitable for design purposes, this acceleration data maybe useful to the NRC.
The data on each file are in a 10E12.4 format (i.e.,10 sequential values per line) with a uniform 0.005 second time increment between values. There are a total of 4762 entries per file.
Units are inches and seconds.
Plots of the data are also enclosed.
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NEC_suestion10:
Discuss difference between single rack and multirack analyses in terms of.
resulting displacements and reactions.
Also, discuss the key procedures and assumptions for developing three dimensional multi-rack model and. provide a basis for considering it as the bounding case.
Discuss sensitivity of the i
modeling in terms of difference in responses between, for example, two rack and F
three rack multi-rack analyses (Page 3-14).
1 Maine Yankee Clarification:
1 The multiple rack analysis model is based on a section across the pool, rather than including the entire pool.
This limitation was imposed to provide an accurate modeling of the individual racks while maintaining a practical level of analytic complexity. The specific section along the west wall was' selected to provide both a variety of rack sizes and the maximum diversity in water gap size.
In addition, this section contains the maximum water gap in the pool, thereby minimizing fluid coupling and maximizing rack seismic displacements.
The model also includes a wide variety cf fuel loadings including empty, full, and unevenly filled racks. The inclusion of wide ranges for these significant parameters provides exceptional insight into the nature of the multirack seismic e
response.
Physically, this 3-D analysis represents a full-width pool with a wall 1
artificially introduced between the first and second rows of racks.
This simplification has little effect on the results.
The following observations 3
form the basis for this conclusion:
From physical principles, there is little reason to expect cross-coupling between the two horizontal directions.
Thus, what occurs in the artificially short direction should not significantly affect the results of interest, namely the response in the. full-width direction. Although a potential for cross-coupling does exist since slipping at the feet is a function of the shear forces in both directions, this is not a concern in f
practice.
This conclusion is reached by reviewing the results summary below which demonstrates that the number of racks in a given direction does not significantly affect these forces. Thus, cross-coupling effects i
truly are small and the esults for the full-width direction should not differ due to changes in the number of racks in the orthogonal direction.
Results Summary Maximum Foot Shear Loads' (lbs)
Rack with Full Fuel Load (Rack B)
Coefficient of Full-Width Short Friction Direction Direction i
0.2 21560 18700
[
0.8 48930 52010 l
' Based on simplified model with 4 feet i
i Ld93mn\\93113 3
The analyses indicate no significant difference between single and multiple rack analyses except for fluid pressures, particularly around the perimeter of the pool. Rack displacements and loads are similar for both analysis models as described in the response previously supplied to NRC i
Question 10 of Reference (d).
This similarity is also seen in the above
?
table when comparing reactions in the single and multiple rack directions.
This lack of sensitivity to the number of racks in the model should extend to the case with additional racks in the third dimension.
As noted above, the only factor significantly affected by performing a multiple rack analysis is the fluid pressure at the pool walls. This is discussed in the written response to NRC Question 11 of Reference (d).
As noted in that response, this pressure is also a function of how much fuel is in the racks.
In these evaluations, the pressures computed at the pool walls have-been conservatively factored upwards to accoutit for the maximum number of fuel bundles stored in the E-W or N-S directions.
3.
F C Ouestion 13:
It is stated that all computer programs utilized in performing the rerack analysis were verified.
Provide the code verification documents (both experimental and analytical) which apply to the current usage for rack responses (e.g. nonlinear dynamic analysis and large deformation buckling analysis).
Also, provide information with reference to the code quality assurage (QA) program and discuss whether the QA was reviewed and approved by the NRC staff.
Also, indicate whether or not the QA documentstion is available for a staff audit. The report also stated that the ANSYS code was reviewed and approved by the NRC. Please provide the reference for the approval. Discuss the extent to which the current rack application is consistent with the capability and limitation of the ANSYS code.
liaine Yankee Clarification:
The ANSYS structural engineering analysis computer program is appropriate for the structural evaluation of the proposed fuel racks because:
It contains, as standard proven features, all the modeling and analytical capabilities required to evaluate the seismic response of submerged fuel racks.
It is a well-established and widely-used analysis tool with a proven record of seismic Category I nuclear component and nuclear structure design validation during the past two decades.
The software vendor has a Quality Assurance program which conforms to Appendix B of 10CFR50.
This program has been reviewed, audited and approved by Stone & Webster in accordance with its NRC-approved Standard Nuclear Quality Assurance Program, SWSQAP 1-74.
It has been used to qualify existing, licensed, spent fuel _ storage racks.
Also, examples of nonlinear fuel rack response evaluated using ANSYS are discussed in NUREG/CR-5912, Review of the Technical Basis and Verification of Current Analysis Methods Used to Predict Seismic Response of Spent Fuel Storage Racks. The number of organizations independently selecting ANSYS for the evaluation of fuel racks reinforces our belief that it is appropriate.
L:\\93mn\\93113 4
r e
O ANSYS has been used extensively in many industries. This wide user base enhances the identification of any. subtle coding defects and provides the basis for the vendor to provide the most widely -analytically verified program possible.
The program has an extensive variety of output options, especially graphical, which strengthen the user's ability to review the behavior of the analytical model for assurance that it responds in a physically realistic manner. The results of the analyses for the Maine Yankee racks i
have been thoroughly reviewed to assure they are realistic.
i 1
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