JPS62259099A - Cask for for radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radioactive waste cask equipped with street-resistant skirts at both closed ends.

Radioactive waste casks are classified into two types called A type and B type.

Each category must be able to withstand some degree of impact force and other conditions, such as internal or external heat. The B-type cask, to which this application is primarily concerned, has a substantial non-yield surface of 30 feet (approximately 9
．． It must be able to withstand the impact forces applied when masonry is carried out from a height of 15 m) in the positions described below.

An example of a cask end that absorbs impact energy is 1. from the flat top or bottom end; 2. from the corners of the top or bottom end; 3. from the sides. This is disclosed in the issue. According to this disclosure, the cask for transporting fuel assemblies is equipped with a shock absorbing piston member on the lower side.
It consists of two metal plates spaced apart from each other, a number of hollow metal bodies stacked one above the other between the metal plates, and mounting means for attaching the piston member to the lifting device. If the transport cask were to fall,
The hollow metal body is deformed. As a result, energy is dissipated and the force exerted on the cask during impact is not only temporarily but completely reduced. Thus, the transport cask subsequently slows down rapidly and no longer springs up. That is, the key here is to use a material that has relatively high deformation energy and can withstand sufficient plastic stretching or expansion before failure, and with enough room for this plastic stretching or expansion to occur. is obtained through the aforementioned cavity. Also, U.S. Pat. No. 3,675,748 discloses a deformable impact energy absorbing means for use in a spent nuclear fuel transportation cask. This absorption means is composed of a large-diameter tube 12, and a plurality of small-diameter tubes 14 are filled in the tube 12. According to this disclosure:
As the cross-sectional area of the r-tube 12 decreases, the resistance to deformation increases accordingly as the tube 14 deforms further. This increase in resistance to deformation increases at a readily predictable, approximately linear rate with respect to deformation, as illustrated in FIGS. 3 and 4. The tube can also be made of stainless steel or other ductile high strength steels, metals, or alloys. Further, U.S. Pat. No. 4,423,802 discloses a cask end cap. The cap is formed with a number of different compartments defined by sheet metal members. A portion of this space is made of a soft damper material such as balsa wood, and the rest is made of a hard damper material such as hardwood.

In the inventor's personal opinion, such an approach of absorbing impact energy through the use of easily fractured structures, such as foamed materials and honeycomb structures, as well as the disclosed example, is in many respects ineffective. It is inferior to that of the invention. With these materials and structures, pressure and energy absorption increases as a function of displacement. At the highest pressure, most of the energy is absorbed in the final stages of fracturing. As a result, the deceleration force and deceleration itself become large.

It is therefore an object of the present invention to provide a relatively constant shock absorbing means for a cask whose deceleration rate is subject to the constraints of its geometry.

According to the present invention, there is provided a roughly cylindrical cask for radioactive waste, and impact-resistant military skirts are fitted at both ends of the cask, and the skirts are made of solid, soft, and lightweight metal. It consists of a one-piece member having a general cup-like profile with a bottom and sides, and a skirt is fitted over one end of the cask and tensioned a predetermined distance in the axial and radial directions. Provided is a cask having a predetermined wall thickness along the sides and ends of the cask, wherein the volume of the metal material exceeds a volume that is likely to be crushed in a prescribed drop test. .

Further, according to the present invention, the approximately cylindrical B for radioactive waste is provided.
an impact-resistant skirt adapted to fit over each end of a cask of the type, made of a solid, soft, lightweight metallic material, having a generally cup-like profile with a bottom and sides; A skirt is also provided, characterized in that it is constructed from an integral member having a.

Most metals exhibit a pseudo-material property sometimes called "dynamic flow pressure." This "dynamic flow pressure" is defined as the energy required to displace a unit volume of material, and is
It has dimensions of 3 inches or psi.

The dynamic flow pressure is relatively constant over a wide range of metal displacement and is slightly greater than the compressive yield strength of the metal. Although this dynamic flow pressure must be determined experimentally, it allows the absorbed energy to be related almost directly to the displacement of the metal, greatly simplifying impact analysis.

Preferably, the impact-resistant skirt is made of aluminum, beryllium or magnesium, or an alloy of one of these metals.

Most Type B radioactive waste containers are cylindrical because they are more resistant to impact than rectangular containers.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a cylindrical cask, generally designated by the reference numeral 10, is comprised of a side wall 12 and two end walls 14. Very shallow cup-shaped impact resistant skirts 16 fit over each end of the cask 10. 1 each skirt
6 is constructed of an integral member made of a solid, soft and lightweight single metal material such as aluminum. As can be seen in Figure 1, the inside corners of the skirt fit into the corners of the outside end of the cask. For purposes of illustration, the axial extension of the skirt along the sidewall 12 is designated by the numeral 18 and the radial extension of the skirt along the end of the cask is designated by the numeral 20.

The skirt is also secured to the cask with a rond turnbuckle member 22.

We believe that the present invention is best understood through a mathematical analysis of street walls and energy absorption. Accordingly, most of the following description attempts to explain the invention in such an analysis.

The energy absorbed by the cask and skirt is: KE-PE-(30+d) X 12 X W
It is expressed as (1). Here, KE - Kinetic energy PE - Potential energy d - Impact following displacement W - Weight of transport package The velocity of an object falling from a given height upon impact (ignoring aerodynamic drag, etc.) is v - Ji7 (2) It is expressed as Here, V: Velocity at the time of impact g: Gravitational acceleration D: Falling distance The deceleration becomes the lowest when the object undergoes constant deceleration. This is because in that case the deceleration will be a function of the distance over which it occurs. The relationship between constant deceleration, distance and speed is expressed as V -2(3). Here, since equations (2) and (3) are equivalent: a', constant constant speed, speed', and deceleration distance, the following relationship is obtained for a constant deceleration force.

gD-a'D' (4) Set the falling distance to 30 feet (approximately 9.15 m), g-32,2ft/
5ec2 (=9.8m/5ee2), the relationship for constant deceleration is expressed as follows. Here, D' is in inches.

For foams, lightweight materials, honeycombs, and other materials that fracture relatively easily, the deceleration force is a function of displacement; in the extreme case, a' is directly proportional to displacement, and the final deceleration is It may be twice the value. In such cases, the following formulas apply: Here, the maximum deceleration of a'', D'' is the displacement distance.

2gD=a#D' (6) For the same falling distance and gravity used to obtain equation (5), the equation for maximum deceleration is:

FIG. 2 is a graphical representation of deceleration force as a function of fracture distance. Curve 24 is for a constant speed, and curve 26 is for a case where the deceleration force is proportional to displacement.

For each direction of fall, i.e. falling from the edge, side and corner, the volume of the crushed material and the projected area of the fracture are the main factors used to determine the deceleration force, and these factors is related to the shape and dimensions of the skirt.

Referring to FIGS. 3 and 4, a cask with an impact-resistant skirt is shown oriented to fall from a flat end. For this flat end fall, the fracture volume is simply the product of the fracture area and the displacement. In many cases, skirting material that extends beyond the projected area of the cask contributes.

do not have. In high-impact situations, the skirt material may be displaced without fracture, and therefore does little to absorb energy.

The main formula for analyzing a fall from such a flat end is: Fracture volume = (R1'-R2') πx d
(8) Fracture area” (R1'-R2')π
(9). The shaded areas in FIGS. 3 and 4 represent the crushing volume and crushing area, respectively.

Referring now to FIGS. 5 and 6, the cask is shown oriented to fall from the side, and the crushing volume and crushing area are schematically illustrated as hatched areas. The formula applied to this fall from the side is the following formula (1
0) to (12).

Crushing area = 4R3SinφW (11)
Displacement・R3(1-cosφ) (12
) In FIG. 7, a hatched area showing a cross section through the fracture volume along the plane of maximum material displacement is illustrated.

In FIG. 8, the shaded area represents half of the shaded area projected from FIG.

For a fall from a corner at 45°, the formula %Formula % For falls from a flat bottom and top only, a constant deceleration is obtained using a material with constant dynamic flow pressure. For side drops and corner drops, the impact area increases as a function of displacement, so the deceleration will increase in direct proportion to the impact area. In the case of drops from the top and bottom ends, the deceleration rate is approximately constant, so the displacement can be varied by increasing or decreasing the inner diameter of the impact-resistant skirt. In other words, the skirt portion 20 extending radially from the end can be increased or decreased. Similarly, the displacement during side fall can be varied by varying the distance that the skirt section 18 extends axially along the outer wall 12 of the chassuf.

For the purpose of a detailed explanation of the invention by applying the formula 1 to a specific example, a cask of type B is 48,0
Assume that it has a weight of 00 Bond (approximately 21,770 kg) and a radius (R1) of 33 inches (approximately 0.84 m). The impact resistant skirt in this example is 15,000 psi
Dynamic flow pressure (DFP) of (approximately 1054 Pa) and 39
radius (R3) of inch (approximately 0.99 m) and radius (R3) of 2 inches (about 0.99 m)
0.05 m) (7) Solid aluminum with a radial profile 20 and a 6 inch axial overlap 18. Of course, the falling distance is 3
0 feet (approximately q, tsm), with a tolerance of 0.5 feet (approximately 0.15 m). Applying equation (1), the kinetic energy is 17.568X106
It can be seen that it will be an inch bond (1,98X 106J). Since kinetic energy is equal to the product of the crushing volume and FP, the crushing volume is 1,171.2 inches 3 (approximately 0.
0192m3). By substituting the known value of the crushing volume R3 into equation (13), the angle φ when falling from the corner becomes 4Q, 12°. At that time, (14
) formula, the crushing area in this example is 448.6 inches2 (
It can be seen that the area is approximately 0.288 m2).

The three equations other than resting that are useful in determining the validity of the impact-resistant skirt in this example are: Deceleration force (OF)・Area x DFP C
16) Deceleration (DEC) g Ill [lF: W
(17) Solving these equations, the deceleration force is 6
．． 7 x 106 (29,8E + 6N), the deceleration is 139.6 g, and the displacement is 6.49 inches (about 0.16 m). The material obtained from the crushed corner is 8
．． Since it is calculated to be 49 inches (approximately 0.22 m), the displacement of the material is 76.496.

For the case of falling from the side and falling from the flat edge in this example, the corresponding important values are equations (8) to (12) and (
It can be calculated from equations (16) to (18).

The volume of each impact-resistant skirt can be easily calculated and converted to the weight of the skirt. In this example, the converted weight is 1.82 for the two skirts.
It is calculated to be 3 bonds (about a2 akg).

With the present invention and dynamic flow pressure, a solid, soft and lightweight metal impact resistant skirt is shaped to optimize weight to deceleration forces to the specific values required for cask protection. Dimensions can be given.

Optimization is not easily possible, if not impossible, when using foam or honeycomb materials.

This is because such materials alone do not provide a shape that allows for free standing. Also, with foam and honeycomb materials, deceleration forces and energy absorption vary with compressive force, and complex computer programs may be required to analyze such structures in impact conditions.

FIG. 9 illustrates an example of how an impact-resistant skirt may be configured to reduce weight while providing sufficient street rock protection. The outermost corner of the impact skirt, indicated by reference numeral 28 in Figure 9, is chamfered because the amount of material displaced during corner fracture is small until appreciable displacement occurs. be.

The slope section illustrates the depth of the fracture volume in the case of a fall from a corner.

For purposes of calculation, assume that 5 inches of material is removed in each direction from the outermost corner of a high impact skirt that is identical to the high impact skirt of the first example. The calculated weight removed from each skirt is then 373 bonds (approximately 16
9 kg).

By calculations similar to those made in the first example, in the case of a fall from a corner, the area, deceleration force, and deceleration are all approximately 9.
It can be seen that the number increases by 8 zero. The displacement is about 8.6! , so the increase in displacement is approximately small. The important result obtained by changing the geometry in this way is that the deceleration increases by only 9.8% while the weight increases by 20%. This also means that connections will be reduced.

It is also possible to provide different geometries.

For example, by adding material such as that shown by the dashed triangle 30, the weight of the skirt increases slightly but reduces the deceleration force in the event of a side drop.

The idea is that during displacement the area of the material subjected to displacement increases in the circumferential direction but decreases in the axial direction, so that it remains more constant.

[Brief explanation of drawings]

FIG. 1 is a fragmentary, schematic and isometric cross-sectional view of a cask fitted into an impact-resistant skirt; FIG. 2 is a graph illustrating the relationship between deceleration force and crushing distance for two different types of deceleration. Figure 3 schematically illustrates the volume of the skirt that is subject to fragmentation when falling from a flat end face, illustrating one end of the cask of Figure 1 fitted with an impact resistant skirt; FIG. 3 is a schematic side view with parts removed. FIG. 4 is an end view of the end of the cask of FIG. 3 illustrating the area of the skirt subjected to fracturing; Figure 5 shows the cask fitted with the impact-resistant skirt of Figure 1 oriented to fall from the side, and shows the portion of the skirt that would be subject to fracture in the event of such a fall. It is a schematic side sectional view shown. FIG. 6 is a cross-sectional view taken along line IV--IV of FIG. 5, illustrating the area of the skirt that would be subject to fracture if dropped from the side. FIG. 7 is a fragmentary schematic diagram illustrating the portion of the skirt that would undergo fracture if dropped from a corner at 45°. FIG. 8 is a diagram showing half of the fracture area when falling from a corner. FIG. 9 is a fragmentary schematic diagram illustrating a skirt cross-section with some optimization in terms of weight reduction of the impact-resistant skirt. 10...Cylindrical cask 16...Impact-resistant skirt 18...Axial extension part 20...Radial extension part

Claims (1)

[Claims] 1. A roughly cylindrical cask for radioactive waste, with impact-resistant skirts fitted at both ends, the skirts being solid, soft, and lightweight. It consists of a one-piece member made of metallic material and having a generally cup-like profile with a bottom and sides, and a skirt that fits over one end of the cask and extends a predetermined distance axially and radially. A cask having a predetermined wall thickness along the sides and ends of the cask that overhangs, and having a volume of metal material exceeding a volume that is easily crushed in a prescribed drop test. 2. The cask according to claim 1, wherein the bottom of each cup has an open central portion. 3. The cask according to claim 1 or 2, wherein the entire outer surface of the cup bottom is substantially perpendicular to the entire outer surface of the cup side. 4. The cask according to claim 1, 2 or 3, wherein the outer surfaces of the bottom and side portions of the cup are joined by a chamfer of about 45°. 5. Claims 1 to 4, characterized in that the side of the cup overhangs from the side of the cask by a distance longer than the length that the bottom of the cup overhangs from the end of the cask. Casks listed in any of these sections. 6. The cask according to any one of claims 1 to 5, characterized in that the cask is a cylindrical B-type cask. 7. The cask according to any one of claims 1 to 6, wherein each of the impact-resistant skirts is made of aluminum. 8. An impact-resistant skirt adapted to fit on each end of a generally cylindrical type B cask for radioactive waste, made of a solid, soft and lightweight metal material, A skirt characterized in that it is constructed from a one-piece piece having a generally cup-shaped profile with a bottom and sides. 9. The skirt of claim 8, wherein the bottom of each cup has an open central portion. 10. The skirt according to claim 8 or 9, wherein the entire outer surface of the cup bottom is substantially perpendicular to the entire outer surface of the cup side. 11. Claim 8, characterized in that the outer surfaces of the bottom and side portions of the cup are joined by a chamfer of approximately 45°.
The skirt described in item 9 or 10. 12. Claim 8, characterized in that the cup has its sides overhanging the sides of the cask by a distance greater than the length by which its bottom overhangs the ends of the cask.
A skirt described in any of Items 1 to 11. 13. The skirt according to any one of claims 8 to 12, characterized in that it is made of aluminum.