ML20235V893
| ML20235V893 | |
| Person / Time | |
|---|---|
| Site: | 07109792 |
| Issue date: | 10/13/1987 |
| From: | Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20235V862 | List: |
| References | |
| NUDOCS 8710150370 | |
| Download: ML20235V893 (8) | |
Text
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m pn atam o, UNITED STATES E[i - .- ~ ~ ?> NUCLEAR REGULATORY COMMISSION h .' ,.3 WASHINGTON, D. C. 20555
/
Safety Evaluation Report Department of Energy _
Division of Naval Reactors Model No. Model 1 DIG Core Basket-Thermal Shield Shipping and Storage Container Docket No. 71-9792 l
SUMMARY
By application dated May 14, 1986, as supplemented, Department of Energy, Division of Naval Reactors, requested design approval of the Model No. Model 1 >
DIG Core Basket-Thermal Shield (CB-TS) Shipping and Storage Container package.
Based on the statements and representations contained in the application and J the conditions listed below we have concluded that the Model No. DIG CB-TS Shipping and Storage Container package meets the performance requirements of 10 CFR Part 71.
REFERENCES
- 1. DOE, NR, application Dated May 14, 1986.
- 2. DOE, NR, supplement Dated September 25, 1986.
- 3. DOE, NR, supplement Dated December 3, 1986.
- 4. DOE, NR, supplement Dated March 27, 1987.
- 5. DOE, NR, supplement Dated September 23, 1987.
DESCRIPTION The Model No. DIG Core Basket-Thermal Shield (CB-TS) Shipping and Storage ;
Container package is a right circular cylinder 198 inches long and 115 inches !
in diameter with access for loading provided by a removable closure head. The ,
container consisting of the cylindrical side walls and the bottom end has a l three layer construction with a steel inner vessel approximately nine inches thick covered with approximately nine inches of reinforced concrete which is encased by a 3/8-inch thick outer shell. The CB-TS is secured in place inside the container with an 8-inch thick steel preload plate which is bolted to the inner vessel with 72 high strength bolts.
Closure of the containment vessel is provided by the 6-inch thick steel closure head which is fastened to the inner vessel with 72 high strength ,
bolts. A steel closure ring is welded over the bolts and provides containment.
C
An inner impact limiter and an outer impact limiter are attached to the container to reduce damage in the event of container accident. The inner impact limiter is a stainless steel section which lands on the top surface which seats on the top plate of the outer vessel.
The shipping container is transported with its axis horizontal and is i
supported by a shipping skid. The loaded container assembly weighs l
approximately 160 tons. The combined weight of the loaded container and skid ' '
is 195 tons.
. DRAWINGS The packaging is constructed in accordance with General Electric Company Drawings contained in Appendix 2.10.4 of the application.
CONTENTS One irradiated DIG core 1 core basket-thermal shield essembly with up to 20 gallons of residual water and surface contamination in the form of activated corrosion products.
STRUCTURAL A. General Standards for all Packaging Minimum Package Size The pa'ckage meets the requirements of 10 CFR 671.43(a) for minimum sizes.
Tamperproof Feature ..
I The closure head of the package is closed by 72 bolts;1.50 inches in diameter on,d a closure ring which welded to the inner vessel and the cicsure plate completely covering the bolts. Thus, no tamperproof device
- is required.
Positive Closure The package is closed by bolts and weldss ,
Chemical and Galvanic Reaction
((
The package is constructed of such materials that there will be no chemical, galvanic, or other reactions between package components and contents.
General Requirements The package meets the requirements stipulated in 10 CFR 671.43(f) as evidenced by the analysis of each condition under the normal conditions of transport.
q 9
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- i. ,
a
. Valves or Other Devices i The package does not have any valves to allow' radioactive contents to escape. The_ bottom drain and the vent hole in the closure head are closed by pipe plugs which'will' require tools for their removal.
B. Lifting and Tie-Down Standards for. All Packages The applicant has'shown by analysis that package can be lifted by a specially designed lifting beam and fourteen,1.5 inches diameter studs which are threaded through the bolts holes of the closure head into the inner ' vessel. ' After the, package is loaded'and the closure ring is welded in place, however, the package will have no lifting devices.
Tie-Down Devices The applicant has shown by analysis that the tie-down devices (Shipping
- skid and wire-rope cables) meet the requirerrents of 10 CFR 571.45(b).
C. Normal Conditions of Transport' Heat ,
The.resulting stresses due to differential thermal expansion and-internal pressurization are low compared with the design. allowable stresses.
Thus, the' hot environment (heat) requirement has no adverse effects on the package.
Cold The application states that the containment vessel is made from A352, LC2-1 Cast Steel which has a Nil ductility transition temperature (TNDT) equals to -80*F. This conclusion was reached based on Charpy impact test results. However, in accordance with .the NRC Draft Regulatory Guide
, entitled " Fracture Toughness Criteria for Ferritic Steel Shipping Containers With a Wall Thickness Greater than Four Inches (0.1m)," TNDT is approximately -140 F for lowest. service temperature (LST) of -20 F and
- at the greatest cask thickness. Thus, for TNDT = -80 F, the LST should not be lower than 40 F in order to maintain the same relationship of LST - TNDT = 120 F. The applicant has proposed an administrative control so that the package can only be shipped when'the daily average temperature is higher than 40 F. Considering the very large size of the package and the' time required to change cask temperature, this is a viable approach of meeting the fracture toughness criteria. Therefore, a license condition has been imposed on the package that it can only be transported
, un days that the average temperature is not less than 40 F.
Reduced External Pressure and Increased External Pressure This regulatory requirement has no significant effects on the package as shown by analysis.
- 4. '
i Vibrations The natural frequency of the transport vehicle (railcar) does not lead to {
o resonant frequency in any of the package components. Thus, vibrations incident to normal transport should not have any significant effects on package.
Water Spray The package is of all welded steel construction. There are no gasketed joints, aperatures, and valves through which water may gain entrance.
Therefore, the water spray condition will have no effects on the package.
l Free Drop The applicant performed computer analysis to show that one-foot free drop of the package in the orientation that the package is normally i transported (horizontal) does not compromise safety. Because of the ~
massive, all steel welded construction of the package, damage due to the one-foot drop is not significant.
l Corner Drog Not applicab~1e Compression Not applicable Penetration The 13-pound cylinder dropped from a' height of 40 inches does not possess sufficient energy to damage the container.
4 D. Hypothetical Accident Conditions Free Drop The applicant presented computer analysis results of: 1. top and bottom flat end drop, 2. side drop, 3. top and bottom C. G. over corner drop, and
- 4. oblique top and bottom drop. The analyses are based on the balanced energy method (i.e., impact energy is absorbed by crushing the impact l limiter or the container material). The primary purpose of the package i is to retain the CB-TS assembly inside the inner vessel so that both the radiation level and radioactive material release will not exceed the acceptance criteria of 10 CFR Part 71 under the accident condition. In this regard, it is important to demonstrate that the closure head will remain attached to the inner vessel. The CB-TS assembly is secured in the inner vessel by 72, one inch diameter pre-load ring (or plate) bolts. The closure head is attached to the inner vessel by another 72,1-1/2-inch diameter closure bolts.
In addition, a closure ring is added to the top of the closure head covering the closure bolts and is welded to the closure head and the inner vessel. The analysis presented in the SARP addendum dated September 1987, has shown that following the hypothetical flat top end drop accident with'a calculated crush force equals to 362 g's, the combined strength of the pre-load bolts closure bolts and the closure ring welds are sufficient to resist the total outward impact force acting on the closure head. The analysis is.very conservative since it neglects the impact force of the top impact limiter which is acting in the opposite direction of the closure head impact force. The equivalent g
- force for top corner drop is 102 g's and for side drop is 203 g's.
Independent calculation by the staff has shown that the closure system (pre-load bolts, closure bolts and closure ring welds) are strong enough to preclude separation of the closure head from the inner vessel.
For the flat bottom end drop, the finite element analysis has shown local high plcstic strains at the boss near the center of the container. The resultant plastic strain exceeds the ultimate strain of the container ,
material through approximately half of the thickness of the inner vessel. Instead of demonstrating that the inner vessel would not break open or lose a significant amount of shielding, a 12-inch diameter hole completely through the center of the bottom of the inner vessel was l assumed and analyzed for shielding. The staff agrees with the applicant
-that this is a conservative and acceptable approach.
Puncture -
Puncture damages from the 40-inch free fall upon the 6.0-inch diameter pin are minor with respect to physical damages to the package. The analyses are based the energy balanced method taking into account of strain rate effects and increased area when crush the' punch pin. The peak force obtained this way was then applied to the inner ve:sel and the closure head to show that a shear failure would not occur and the closure i head would not collapse. The reinforced concrete outer vessel was 4 conservatively-neglected in the analyses.
s-Thermal
.No significant damages from the 1475 F fire to the package components ;
occurs. The staff agrees with the applicant's conclusion that stresses j induced by temperature and pressure does not compromise package safety. )
Immersion This regulatory requirement does not have any effects. on the package.
l
. CONTAINMENT 4 f !
The primary containment boundary for the Model No. 01G CB-TS package l l consists of an inner vessel and closure head. The interface between the ,
inner vessel and closure head is sealed with two concentric 0-rings. A I
i
vent hole in the closur'e head-and a drain line at the lower end of-the inner vessel are- the only penetrations through the containment boundary.
Both are used only during loading and unloading the container and are ,
closed by two pipe' plugs in series during shipment.
The major sources of radioactivity within the Model No, DIG-CB-TS package are the irradiated cere basket and thermal shield and the activated corrosion' deposits (crud) adhering;toboth. The total activity of the crud adhering to the core-basket and thermal shield has been estimated 1 to be approximately 45 curies.) The only radioactivity which could be released during normal or accident conditions is the crud that has been loosened by shock or vibration. The applicant has estimated from test results on a S5W assembly that only 0.1% of the crud could be loosened by-the regulatory. accident conditions.- Using these test results, the quantity which could be' released during accident conditions has been calculated to approximately 1/400 of the release permitted under 10 CFR i
-971.51. None of the activity from the irradiated core basket or thermal i shield themselves would be subject to leakage as the inner vessel and ..
closure head would remain intact during hypothetical accident. The Mcdel No. 01G CB-TS package therefore meets the containment requirements (of an A quantity per. week release) for hypothetical 2ccident accident conditions c$ntainin10CFRPart71.
The containment. requirement of 10 CFR 571.51(a)(1) has been met by demonstrating that the sealing surface surrounding the 0-rings remains in undamaged during normal transport conditions. The 0-rings and pipe plugs are tested for proper sealing prior to each shipment. Because of the limiter quantity and form of the material available for possible release, and the fact that the sealing surface is undamaged during normal transport conditions, the applicant has demonstrated that the Model No, DIG CB-TS. package meets the containment requirements for normal transport
. conditions contained in 10 CFR Part 71.
THERMAL w
Normal Conditions of Transport Due to the low heat generation rate of the package's contents, the maximum package temperature achieved during normal transport conditions is determined primarily by the absorbed solar flux and package emissivity. The following ,
temperatures were calculated for normal operating conditions (100*F ambient, i solarinsolation):
Component Temperature F .
Core Brsket-Thermal Shield 319 Inner Steel Shell 214 Concrete Shield 208 Outer Steel Shell 164 '
l m-a._ _ _ .
In this' temperature range, there were no appreciable problems with either thermal stresses or material properties. Since the container is assumed to hold 20 gallons of residual water, the internal pressure weeld be increased by 21 psi.
(AccicentConditions
~The Model No. DIG CB-TS package was also analyzed ~for the 1/2-hour, 1475*F fire accident conditions. The maximum temperatures calculated for fire accident conditions were: '
Component Temperature *F Core Basket-Thermal Shield 325 Inner Steel Shell 276 Concrete ShieM - 320 Oute: Steel Shell 1323 None of the package's structural components exceeded their melting points and there were no combustible materials. The average temperature inside the package was less than 350 F, resulting in a maximum pressure.(from the residual water and air expansion) of approximately 55 psig. Failure of the 0-rings seals would result in venting of the container and pressure relief.
(Seal failure in the event of accident conditions was shown to be acceptable for containment requirements.)
The applicant has demonstrated by analysi? that the Model No. 01G CB-TS package meets the thermal requirements of'10 CFR Part 71.
SHIELDING (a) Source term The contents are ncn-fissile end consists primarily of an irradiated-structural component assembly. A much smaller amount of radioactivity is expected to be present in the form of loose and fixed corrosion products. Determination of the assembly curie .
content was established by use of the ORIGEN (ORNL) ccmputer orogram for the structural component immersed in a neutron flux and power level characteristic of the reactor and its time of operation. The ganna source is essentially that due to Co-60. A conservative factor of 1.5 was included for uncertainty in the source strength determination.
(b) Dose rate estimates The above source is discretely defined within a right circular cylinder (16.5 ft high, 9.5 ft diam) shielded by steel and concrete.
1
o The applicant has used the Westinghouse Point-Kernel 3-D computer program SPAN-4-A to calculate garana dose rates at the sur' ace of the Model No. DIG.CB-TS pactage for normal conditions and at 3-foot distant from the package surface for accident conditions of transport.
The side contact dose rate was calculated to be 29 mrem /hr. Three-foot distant from this point, assuming a (1/r) gamma flux fall-off in air, the gamma dose rate under normal conditions would be 17.7 mrem /hr.
The applicant has also calculated under the worst accident condition, at three-foot distant from the cask surface, the maximum dose rate is 980 mrem /hr.
A condition, before shipping that most be met therefore is: gamma dose rate measured at three feet from the cask surface must satisfy the following relationship:
(980) X ('tI-dose rate measured at 3 ft from surface) 4.1000 mrem /hr.
(17.7)
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OPERATING, ACCEPTANCE, AND MAINTENANCE General operating procedures for use of the package are provided in Section 7 of the application.
General acceptance and maintenance programs are described in Section 8 of the application.
CONDITIONS ,
- 1. Preloading of the preload plate and the closure head and sealing the container must be done with a temperature at or above +40'r.
- 2. Shipment shall be made when the average daily temperature is above +40 F.
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- 3. Shipment applies only to 01G Core 1 CS-TS which was removed CY 1975.
4 (980) X (2(-dose rate measured at 3 ft from surface) 4.1000 mrem /hr.
(17.7)
CONCLUSION Based on our review, the statements and ra presentations contained in the i application and the conditions listed above, we find that the Model No. Model 1 DIG Core Basket-Thermal Shield Shipping and Storage Container package meets the requirements of 10 CFR Part 71.
? va bf a ChdlesE.MacDonald, Chief Transportation Branch Division of Safeguaros and Transportation, NMSS Date: E 10 E