ML20155H170
| ML20155H170 | |
| Person / Time | |
|---|---|
| Site: | 07106639 |
| Issue date: | 10/22/1987 |
| From: | Mauck C ENERGY, DEPT. OF |
| To: | Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20154C352 | List: |
| References | |
| 28711, NUDOCS 8810180304 | |
| Download: ML20155H170 (9) | |
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Department of Energy
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Washington, DC 20545 OCT 2 21o87 a
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RECGVED pj W
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lir. Charles E. liacDonald Chief, Transportation Branch Q up,'d
- Division of Safeguards and Transportation
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U.S. Nuclear Regulatory Comission l i.s.v' Washington, D.C.
20555
Dear Mr. MacDonald:
P In response to the Nuclear Regulatory Comission's (NRC) comments on the itH-1A package in the letter of May 22, 1985, to Mr. David LeClaire, we are submitting to you six copies of a revised Safety Analysis Report for Packag-bg (SARP) for your consideration in the continuing review of the MH-1A for certification. Enclosed also is a summary of the NRC concerns and the DOE response with references to the sections cf the SARP that address the con-cerns in detail. We would like to b ing to your attention that the load limiting system of redwood has been.umpletely redesigned and replaced with a l
foan system, a new structural analyses for the normal environment and acci-dent environment are presented and the containment system has been redefined with credit being taken for the fuel form in maintaining any leakage within l
the regulatory requir aents.
The DOE Certification staff has not reviewed the new SARP or responses to your comments as it is necessary that the SARPs be forwarded to your office r
a as soon as possible for your staff's continuing review.
I will appreciate
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your advising me of the status of the review and of any support our staff may i
provide in response to any additional comments of your staff or provide additional information as required.
i Sir,cerely, N
L Charl -
Hauck, Chief Packaging Certification Office i
Office of Security Evaluations ;"
Defense Prograns oclosuris
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BLS_POLLSLSJN CURRENT MH-1 A SAR TO NRC O
QUESTIONS CONQfRNING PREVIOUS (REA) SAR Structural Comment:
1.
On page 1.1-3, the application specifies allowable stress criteria for the cask.
However, the application does not show that the stresses in the cask meet this criteria. Many of the stresses reported in the application exceed allowable values.
The application should show explicitly that the stresses in the cask are within allowable limits under both normal and accident conditions.
Regulatory Guides 7.6 and 7.8 may be helpful in this regard. Also, note that certain bending stresses at the edge joint of the square pressure vessel should be classified as primary stresses (see definition of Secondary Stress in Regulatory Guide 7.6).
Response
1.
The design criteria sectirn was rewritten, and the SARP was modified to ensure that all stress criteria are now adhered to. Normal conditions of transport criterid are set out in Section 2.1.2, Table 2.1.
Hypothetical accident condition stresses, when applicable (generally for payload confinement considcrations), are limited to the ultimate strength of the particular material in question.
All calculated stress levels show positive margins of safety.
6ending stresses at the edge joint of the square inner vessel are treated as primary stresses in relevant analyses.
The basic assumption is that the corner welds are effectively full penetration welds, as shown on Westinghouse Dwg. H-3-57545.
Specifically, see analyses in Sections 2.6.7.2.4 and 2.6.7.2.6.
Coacent:
2.
The discussion presented in the application for oblique drop is not adequate.
The application should evaluate the stresses that would be produced under oblique impact orientations and by secondary impact and show explicitly that these stresses are within allowable limits. Also, application should evaluate the cask in the most dameging angular orientation about its longitudinal axis (i.e., the effects produced by r)tating the square containment vessel).
Response
2.
Oblique drops are now addressed in greater detail.
Normal condition oblique drops are covered in Section 2.6.7.4, and accident conditions oblique drops are covered in Section 2.7.1.4.
The effects of secondary impacts are also discussed in this section.
The worst possible orientation about the cask axis fer oblique drops is conservatively addressed by taking the orientation which will produce maximum impact loads, and then applying these loads in the orientation which would result in maximum stresses, further conservatism is introduced by using the hardest foam with structural material
l 2-properties at 70*F (which will be lower strength than they would be at -20'F).
2 Comment:
3.
The applicatioa does not consider the combined effect of all the loads which act simultaneously on the containment vessel.
For e:tample, the impact analysis should consider the combined effects of impact and ambient temperature (differential thermal expansion / contraction).
Regulatory Guide 7.8 specifies an acceptable set of load combinations.
I
Response
3.
Where applicable, different load cases are now combined.
Relevant load combinations are generally the results of 1
increased exte nal pressure (Section 2.6.4) and results of normal condition drops (Sections 2.6.7.1.4, 2.6.7.1.5, 2.6.7.2.4 and 2.6.7.4. Accident condition load combinations arising from side ar.d) oblique drops are now covered in l
Sections 2.7.1.2.4 and 2.7.1.4, respectively.
Results of temperature variation on certain load combinations are given in Section 2.10.5.3.
Effects of differential thermal expansion on cask integrity are discussed in Sections 2.6.1.2 and 2.7.3.
4.
The application does not adequately consider the following loads in evaluating stresses in the containment vessel:
1 Coment:
a.
The lateral pressure that would be exerted by the lead against the containment vessel under 30-foot end, corner and oblique orientations (the horizontal spring used in the analysis does not adequately model this phenomena).
Respons~e:
a.
for the 30-foot drop cases, there is no containment vessel
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as such. Containment is now provideo by the fuel cladding l
for these cases. Nevertheless, the effects of lead i
interaction on the inner vessel wall were investigate <* for j
the assumed worst-case prop orientation for lateral j
loading, flat side drop.
Results are presented in i
Sections 2.7.1.2 and 2.10.4.3.
Coment:
b.
The axial stresses that would be produced by differential thermal expansion / contraction of the inner shell, lead shielding and the outer shell, i
Response
b.
Axial effects due to differential thermal expansion are
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now discussed in Section 2.6.1.2.
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Comment:
c.
The lateral pressure that would be exerted by the lead against the containment vessel due to differential thermal i
contraction at the -40*F and -20'F temperature conditions specified in 10 CFR 71.71 and 71.73.
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. Response:
c.
Differential thermal contraction effects are now discussed in Section 2.6.2.
Coment:
5.
The buckling evaluation in the application is not adequate to show ths.t the inner shell does not buckle under 30-foot drop test cunditions, a.
The application does not consider possible inelastic bucklir.g (note that stresses in the shell were calculated to be above yield).
b.
The application does not consider the combined effect of all loads that would be acting simultaneously on the containment vessel shell (e.g., impact forces, moments, and shear, lateral pressure of the lead due to impact, and axial and lateral differential thermal expansion / contraction).
c.
The application does not specify c factor of safety against buckling or show the interaction equations that will be used to evaluate the combined effects of different types of loads acting simultaneously.
Raponse:
5.
The issue of buckling of the inner shell, with regard to impact on payload and possible resulting loss of containment l
capability of the fuel, for the 30-foot drop conditions, is now covered in Section 2.7.1.1.1.3.
Note that buckling of the inner shell, as an issue in and of itself, is not a concern for hypothetical accident conditions, since the inner shell is not considered to be a containment boundary.
Localized
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buckling which does not have a serious (containment breaching) effect on the fuel payload, is not c'nsidered significant.
Thus, issues such as interaction and margins of safety against buckling becomo mostly irrelevant.
A buckling analysis for normal conditions of transport is presented in Sectica 2.6.7.1.3.
6.
The presentaticn of the finite element analysis is not clear in that nany important aspects uf the analysis has not been discussed in detail. All assumptions should be stated clearly and justified.
Additional information is needed as follows:
Coment :
a.
Justify the finite element model adequately represents the cask.
Discuss in detail the capabilities of each type of element selected for the model including the input requirements and outout obtained, r
4
Response
a.
Finite element models, as well as modeling limitations and their impact on the various finite element analyses performed, are now fully discussed in Sections 2.6.7.1.2, 2.6.7.1.3, 2.6.7.2.2, 2.6.7.2.3, 2.6.7.4 2.7.1.2.2, 2.7.1.2.3, 2.7.1.7.7,2.10.3 and 2.10.4.
Corment:
b.
Justify the boundary conditions used at the horizontal centerline of cask where all nodes are constrained in all directions for all loading conditions.
Response
b.
This question specifically concerns the previous REA finite element model and is not applicable to the models used in the new SARP.
Comment:
c.
Identify the mechanical and material prcperties used in the analysis for the elements of the model.
Response
c.
Mechanical and material properties used for the elements of the models are now given in Section 2.3.
They are listed specifically for the individual models used in the input portions of Section 2.10.4.
Comment:
d.
Identify the loads and the distribution of loading in each analysis.
Response
d.
Loads and load distributions for each model used are now given in Section 2.10.3.
Comment:
e.
Identify the procedures to combine different loads (i.e.,
R.G. 7.8 load combinations).
Response
e.
Load combinations, when applicable, have now been defined and are accomplished by superposition.
Inertial loads are generally derived by finite element analysis. Other pertinent loads are then combined with these manually.
Details are given in Sections 2.6.7.1.4, 2.6.7.2.4 and 2.7.1.2.4.
Comment:
f.
Provide the rationale of using the average element stress at nodal points instead of using the element stresses directly.
The precedure for averaging stresses at the node where two or more elements connected together is confusing and should be explained in more detail, for instance, it is not cicar how the average stresses are derived for different types of elements connected together or for elements that do not intersect each other in the same plane (i.e., outer shell and the fins),
in addition, the procedure to derive principal stresses and stress intensities at each location should be identified.
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Response
f.
Element stress intensities were esed directly in the fluPac finite element analyses, instead of average nodel stresses, as vas done by REA.
Comment:
7.
Based en dynamic and static test results reported in Sandia Laboratories' Report tio. SLA-74 0159, we believe tha redwood crushing stress used in the impact limiter analysis is nonconservative for redwood crushed perpendicular or at an angle to its wood grain.
Judging from the assumption made for redwood crushed are and the compressibility, it is clear that the small safety margin does not provide aiequate assurance to prevent redwood bottom-out before all the impact energy is dissipated.
In addition, there are rer. sons to believe that the embedded corrugated cylinders will increase the impact force significantly higher than stated in the application.
Response
7.
Questions pertaining to redwood no longer apply.
Impact limiters are now fabricated with polyurethane foam, whose properties are presented in detail in Section 2.3.
Comment:
8.
The application does not analyze the cask for normal transport conditions which could produce governing stress.
Response
8.
flormal conditions of transport are now fully analyzed in Section 2.6.
C::mont:
9.
The application does not report the stresses in the closure bolts or in the drain / vent lines which pass through the lead shielding.
Response
9.
Closure bolt (stud) stresses are now analyzed in Sections 2.6.7.1.5, 2.6.7.2.5, 2.6.7.4, 2.7.1.1.1.2, 2.7.1.2.5 and 2.7.1.4.
Implications of impact loads on cask vent and drain pipes are now discussed in Sections 2.7.1.1.1.1 and 2.7.2.
Coment:
10.
The application does not consider potential displacement of shielding due to "lead slump.'
Response
10.
Potential displacement of shielding due to lead slump is now accounted for in Sections S.6.7.1.3, 2.6.7.1.7, 2.6.7.2.3, 2.6.7.2.7, 2.7.1.1.1.1, 2.i.l.l.2.1, 2.7.1.2.3 and 2.7.1.2.7.
Conment:
11.
The puncture evaluation does not consider potential collapse of the top closure plate c bottom end plate.
Response
11.
Potential collapse of the ca.k lid plate and bottom plate by pin punch are now both fully addressed in Section 2.7.2.
1
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6-Comment:
1 The application does not analyze the stresses in the bottort end plate of the cask or in the bottom plate of the u ntainment vessel.
Rasp e:
12.
The cask outer bottom end plate is now analyzed in Section 2.10.4.1.
The inner vessel bottom plate is now analyzed in Sections 2.6.7.1.6, 2.7.1.1.1.1, 2.10.4.1, 2.10.4.4 and 2.10.5.1.
lhermal Comment:
1.
The emissivity values chosen for the stainless steel appear to be low.
Provide the reference items to justify these values.
Response
1.
The emissivity values for stainless steel have been re-evaluated and are 0.3 over a temperature range of -40*F to 600'F. At 1475'F, the emissivity is 0.4.
These emissivity values were obtained from Reference 1, which has been used by others for similar heat transfer analyses.
The above values are for Type 303 stainless steel surfaces in an "unfinished" or "as received" condition.
For the present evaluation of the MH 1A cask, it was assumed that a value of 0.4 would be more appropriate than 0.3 since, after many years of service and/or at extended periods of high temperature service, the surfaces are probably oxidized and/or worn.
The value of 0.4 was used for the fire shield, except during the 0.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> fire when a value of 0.8 was used to comply with conditions specified in 10 CFR 71.
(1)
Y. S. Tonloukian, Thertrop]mical Ptonerli.es of Hiah-lerpgature Solid hie _riah, Vol. 3. The MacMillan Company,1987.
On tating Prose _d.utei Comment:
1.
Step 42 on pages 7.1-10, and 28; Step 46 on page 7.1-38; and Step 50 on page 7.1-47. provide instructions relative to monitoring cask surface temperature prior to shipment to verify compliance with 971.43(g).
The accessible cask surface, when the cask is assembled for shipment, is the fire shell.
Discuss the rationale for selecting a location above the fire shell to reonitor cask surface temperature.
Response
1.
No provision to monitor surface temperature of the loadeo cask at any point is provided in Chapter 7 in the WHC SAR.
If this is a requirement, then a section in Chapter 3 must be added to define criterie for an operational terperature check and a step added to Section 7.1 in the WHC SAR describing the test method and acceptance criteria.
=
Comment:
2.
In Section 7.3.1, Steps 1, 3, 4 and 5 are not consistent with the conditions being discussed.
Response
2.
Section 7.3, "Preparation of an Empty Package for Transport,"
has Leon completely revised in the WHC SAR.
Comments to Section 7.3 of the REA SAR are no longer applicable.
ActentJnedeltLand Mainienage Prostafg Comment:
1.
Paragraph 8.2.7, Miscellaneous, shculd be expanded to require a check on the moisture content of the wood if initial inspection reveals moisture in the steel sheathing.
Response
1.
These comments are no longer relevant because the redwood impact limiters have been replaced with closed foam icpact limiters.
Urmium Aluainuid_Silicide Foeb Comment:
1.
Your request of April 15 1985, concerning additional fuel types should be incorportted into the safety analysis for the package.
This should include a physical description of the fuel and reactivity Tnalyses as may be appropriate.
Responsc:
1.
All fuel types to be shipped in the MH-1A cask are now described throughout Chapters 1, 2, 3, 4, 5 and 6.
A physical description of the fuel is given in Sections 1.2.3 and 4.3.2.
The criticality analysis results for all fuels is given in Section 6.4.3.
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