ML20137Z127
| ML20137Z127 | |
| Person / Time | |
|---|---|
| Site: | 07109195 |
| Issue date: | 02/27/1986 |
| From: | Cunningham R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Cunningham G GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 8603120487 | |
| Download: ML20137Z127 (7) | |
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Y Distribution: w/ enc 1 FEB 2 71996 RECunningham CEMacDonald RH0degaarden HWLee Docket File FCTC: RHO NRC PDR 71-9195 IE HQ Region V letSS R/F FCTC R/F 00d*b#
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Ceneral Electric Company ATTH: Mr. G. E. Cunninghan P.O. Box 460 Pleasanton, CA 94566
'centlem n:
This refers to your application dated October 31, In34, requesting approval of the fiodel No. 2000 package.
By letter dated April 17,19ES, additional infomation was requested in connection with our review of your application. On July 16, 1985, we ret with your staff and discussed each questinn raised in our Acril 17 letter in sore detail. Ry letter dated Octt 22, 1935, additinnal infomation was provided.
L'e have reviewed the additional infomation provided by your October 22 letter and find the concerns raised in our April 17 letter have not been adequately addressed. The enclosure to this letter identifies deficiencies with regard to the analysis of the package design.
In the absence of infomation upon which to base a finding that the requirer.cnts of 10 CFR Part 71 are ret, your application requesting approval of the Ifndel flo. 2000 package is denied without prejudice. Any resuboission of the application should take into consideration the deficiencies noted in the enclosure to this letter.
You ray request a hearing with respect to this denial within 20 days from the date of this notice. The issue to be considered is whether the licensee adequately provided the infomation requested in the NPC letter l
of April 17, 1905.
l FOP THE U.S. ffUCLEAR REGULAT00Y C0f0!SSIGH l
Orialnal Siancd by l
Richard E. Cunningham 9603120487 360227 l
PDR ADOCM 07109195 Richard E. Cunninghan, Director C
POR Division of fuel Cycle and l
f8aterial Safety, fMSS i
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General Electric Company Model No. 2000 Package Docket No. 71-9195 Encl to ltr dtd: FEB 2 7190s STRUCTURAL 1.
The application did not provide adequate justification for the assumptions and the method of analysis for the overpack structure in the following respects:
a.
The overpack finite element model neglects the stiffeners, gusset plates, space tubes, top interior plate, and the interior cylinder. The presence of these components affects the defomation of the toroidal shell significantly. Justification was not provided that these components can be omitted in the finite element (F.E.) model, b.-
The overpack weighs approximately one-third of the entire package, neglecting the nass of the overpack may significantly alter the dynanic responses of the package. Also, it is questionable that it is conservative to assume that the material properties of the overpack under dynamic loading are the same as those given for static loading. Detailed.iustification or analysis should have been provided to support these assumptions, c.
The description of the inelastic collapse load analysis of the overpack structure is unclear. 75e application should have explained how the displacerient' pa, tern of the toroidal shell was detemined and applied to the F.E. model.
No explanation was provided showing how the collapsed load was derived. When loads instead of displacements were used in analysis, how the distribution of loads was detemined should have been explained.
The application should have provided force-deflection curves for the overpack structure at each of the impact orientations considered in the application. The application should explicitly show how the force-deflection relationship was detemined.
d.
It is not clear why Figure 5.2.1 indicated ruch higher energy associated with one foot corner drop than the one foot head on d rop,
e.
It is not evident why the shape of the collapsed load curves are different in Figure 5.2.1 and Figure A-10.
f.
It should be shown by analysis that the overpack structure may be analyzed statically and that there will be no dynamic amplification for the cask structure, g.
There is no analysis of secondary impact for oblique drop.
It should have shown that the bottom impact limiter will remain attached af ter secondary impact.
. 2.
The accuracy and applicability of the auxiliary model analysis is not clear for the following reasons:
a.
Representation of the spacer tubes by quad elements by first detemining the radial stiffness of these tubes and then calculating an equivalent modulus for the quad elements to duplicate the stiffness is not acceptable'because the spacer tubes have different stiffnesses in the radial and axial directions.
b.
The entire inner shell is fixed against displacenent in the radial direction.
During a side drop, force is applied to the contact area of the cask and the overpack cylinder.
Indentation of the cylinder by cask around the contact area is expected.
3.
The cask analysis is incomplete and inadequate to show that cask design meets the provisions of Regulatory Guides 7.6 and 7.8.
The application states that the evaluation is based on these guides.
The application should have provided the following infomation:
a.
The analysis should consider inner shell stresses from lead pour and cold temperature.
b.
The analysis should address the effects of lead contraction from lead pour and impact on the drain line, c.
It is not clear whether the lead slump has
'en adequately cons ide red.
The application should have shown explicitly how nuch the lead slump will.be.and how nuch lateral pressure the lead will exert on the inner shell during a botton end drop.
It is also noted that reducing the modulus of elasticity of lead to 20% of its original value will significantly reduce the lateral pressure exerted on the shells by lead due to 30-foot bottom end drop, d.
The cask stresses are extremely sensitive to changes of cask model.
For a minor nodification at the seal region, stresses dropped drastically from 81.11 ksi to 31.1 ksi at the cylindrical s hel l. Also, Figure 5.2.3.2 compares the stresses for the cask model and the nodified cask nodel. The nodification is at the top seal region, yet the largest stress change occurs at the botton of the cask away from the region that has been nodi fied. No explanation was provided, e.
It is scen that the stresses listed in Figure 5.2.3.2 are different from those stresses of the cask seal model. The question is which set of stress should be used in the cask evaluation? A procedure to verify the accuracies of the stresses should have been provided.
. f.
The number of stress sections taken on the cask model is insufficient.
For instance, there is no stress section taken at the center of the botton plate and at the botton end of the inner shell for a bottom end impact condition. A sketcn should have been provided of the cask shells, closure, and end plate showing the points for which stresses will be tabulated.
At given axial locations on the cask shells and at radial locations on the end and closure plates, separate points should have been designated on the inside and outside of the cask. The nunber of stress points must be sufficient to facilitate a check on the state of stress of the cask and at critically stressed sections.
f.
The application should have explained why the large bending stresses in the thin cylindrical shell under a head-on impact condition.
9 It is noted that stresses are calculated based on the stresses at outer Gaussian points within the elenent.
Large bending stresses have been resulted for sections where no significant moment should exist (i.e., at closure bolt section). The validity of this approach should have been justified.
h.
The validity of the resultant irpact load and its distribution was not clear.
It is not obvious that the inpact load would remain constant regardless of drop orientations (i.e., head on, corner over C.G., and side drop, etc.).
i.
It is not obvious why the steel has a mass density larger than the lead.
4.
The puncture test should have addressed the cases that the pin strikes directl.y on drain line, the top plate, the bottom plate, the seal region, and the side of the cask.
Pending stress and reduction of shielding should have been evaluated. Note that the penetration test is sequential to the 30-foot drop test.
Therefore, package defornation due to 30-foot drop should have been taken into account in analys;s.
5.
The buckling analysis should have considered all concurrent loads due to impact, thermal, pressure, and bending.
Interaction equation nay be used for ca,bined stress effects.
In addition to a reasonable factor of safety for buckling stress, the analysis should have taken into account the imperfection by imposing a capacity reduction factor.
Since the stress criteria used by the applicant may exceed yielding, both elastic and inelastic buckling analyses should have been performed.
. 6.
The closure bolt analysis should have considered the following:
a.
An analysis on torque requirenents for the closure bolts to maintain leaktightness during nomal and accident conditions of transport.
b.
Allowable loads for bolt were based on the ultimate strength.
Also, the failure criteria and allowable loads used for bolt analysis may be non-conservative (Appendices H and I). To assure safety, the allowable bolt load should have been based on the rules of the ASi1E Code,Section III, Division 1. Appendix F.
c.
The design bolt loads in Table H.1 are very small.
The application should show the derivations of these loads and that they satisfy the equilibrium conditions considering the effects of impact and the weight of the payload and the closure head.
d.
In Table H-1, it is not clear why shear in the tangential direction is not applicable to bolts during a side drop.
e.
In Table I.1, it is not clear why there is no shear force on the bolt during the head-on 30-foot drop.
7.
The tie-down structural model should have been discussed, tia terial and sectional properties of the nenbers should have been provided.
A description of how the loads were applied and the procedures to eliminate compression and bending in the nenbers should have been p rovided.
Since the yield stress for the tie-down rib and pad is 55 ksi, the shear-out stress cannot be 47.6 ksi as shown on page 2-11.
The average primary shear stress across a section loaded in pure shear should not exceed the smaller of 0.6 Fy and 0.42 Fu.
i Also, when different materials.ioined together, the design should be based on the weaker material.
8.
The lifting device analysis is not acceptable.
The application i
should have considered the following in the analysis:
a.
Page 2-94, the section considered is not the nnst critically stressed section (see Figure 2.7.2.3).
b.
Page 2-96, bearing stress would exceed yield if the larger load (44.22 kip) was used.
i i
c.
Page 2-96, the equation for nomal stress on weld is wrong.
d.
Page 2-99 through 2-103, the bolt analysis is confusing and hard to follow.
It is noted that the bolts will sub.iect to tensile and shear forces.
The effects of tensile plus shear should be combined.
Also, the adequacy of the bolt pre-load should be addressed. The torque applied to bolts and the depth of holt engagement should be shown on drawing. As indicated in Iten 6, the design rules of Appendix F may te used.
5-9.
The analysis for shock and vibration is not adequate for the following reasons:
a.
The finite element model used in the analysis is the thennal analysis model in that many structural components have been omitted (e.g., the top and bottom toroid).
Thus, the analysis may be inadequate to provide accurate structural responses.
b.
The analysis has excluded the weight of the content which is approxinately equal to 30% of the cask weight.
c.
Reference 4.22 is merely a draf t report in that the adequacy of the method is not assured. Because of the complexity and unique construction of the Model No. 2000 package, sinply apply the g-load reconmended by the draf t report to the cask appears inadequate.
The application should explicitly show that there is no resonance for the package system during t ransport.
10.
The application should identify the material of inner containers to ensure no chemical, galvanic, or other reaction between the cladding and the container or between the container and the content.
SHIELDING The application has not demonstrated that for the proposed contents the requirements of 10 CFR 671.47(c) are met...
CRITICALITY The reactivity calculations of the fuel naterial did not take into account the lead and ' steel contents of the cask.
OPERATING PROCEDURES 1.
Operations 7.1.6(a) and (b) should be carried out under Operations 7.1.3 prior to loading the packaging with radioactive material.
2.
In Operation 7.1.8(a), the torque valve should be stated.
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u
6-3.
Installation of the drain and vent plugs (Operations 7.1.8(b)),
should require the use of an appropriate pipe thread sealant.
4.
Operation 7.1.9(a) reference to Appendix 8.4 should be Appendix 7.4.
5.
The assembly verification leakage test specified in 7.1.9 is not sufficiently sensitive for the leaktight criteria specified. The applicant should use a test sensitive enough to preclude release of an A, quantity of material jn 10 dag/s.
s, or alternatively, a test havihg sensitivity of lx10- a tm-cm In either case, any leakage greater than the design criteria sensitivity would be cause for corrective action before shipment.
6.
Operation 7.3.l(c) reference to 49 CFR 427 should be corrected to read 49 CFR 173.427.
7.
Opera tion 7.3.4.
Referencing of the regulations should be limited to 49 CFR 173.427 " Empty radioactive materials packaging." The ma.iority of the regulations presently cited are not applicable to
" Empty packaging."
1 ACCEPTANCE TEST 1
1.
Visual Inspection 8.1.1.
Identify the code or standard which contains the acceptance criteria, 2.
The leakage tests specified,in 8.1.3 shnuld be used for acceptance l
and periodic (annual) tests of the containment system.
3.
Test for Shielding Integrity 8.1.5.
The description of the test method should 1,nclude a grid size.
MAINTENANCE PROGRAM A replacement schedule should be specified for the containment vessel seal based on useful seal life.
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