CEP Durable Concrete Radioactive Waste Containers vs. Steel Containers - a study.

by Robert Jackson,  Chief Consultant, Containment for Environmental Protection

A.  CEP - US DOT (Department Of Transport Qualified) Durable Concrete Radwaste Packages.

Reinforced concrete packages were selected for their:

  1.   Extremely long life (durable, high performance concrete is used in all CEP - US containers)

  2.   Superior intrinsic shielding

  3.   Competitive volume and weight capacity,

  4.   Stacking stability, and

  5.   Ease of package recovery from interim storage.

There are two sizes of CEP - US DOT packages suitable for transporting and permanent storage or disposal of radioactive waste. Both packages’ designs are made of reinforced concrete walls with an inner liner. The CEP - US Cube has a 39.4-inch external dimension. The external dimensions of the CEP - US Box are 8 feet long, 4 feet wide and 3 feet 8 ¾ inches high.

B.      Long Life of CEP - US Reinforced Concrete Radwaste Packages.

TABLE 1. LIFETIME COMPARISON OF TYPICAL RADIOACTIVE WASTE PACKAGES.

Radioactive Waste Packages

Estimated Life. (Years)

CEP - US CUBE

500-2000

CEP - US BOX

500-2000

STEEL BOX,     (Qualified for transport)

20-50

WOOD BOX      (Qualified for transport)

10-30

DRUM, 55 GAL (Qualified for transport)

20-50

STEEL BOX

0

WOOD BOX

0

DRUM, 55 GAL

0

Table 1 compares the estimated lifetimes of packagings for radioactive waste. These values are applicable for packagings buried in moist soil. The very long life of the CEP - US concrete packagings, indicated in Table 1, precludes the radioactive material from migrating into the water table for a much longer time than steel and wooden packagings. Thus, the CEP - US (Containment for Environmental Protection) packagings for radioactive waste storage and disposal will greatly aid in meeting the goal to implement a focus on safety for the environment, the work force, and the public.

C.      Inherent Shielding of CEP - US Reinforced Concrete Radwaste Packages.

The thick concrete walls of the CEP - US packagings provide much more shielding than the metal packagings. This is illustrated in Table 2.

TABLE 2. SHIELDING COMPARISON OF RADIOACTIVE WASTE PACKAGES.

 Radioactive Waste Packages

Fraction of radiation

 

 

Transmitted

Shielded

CEP - US CUBE

 

 

L/Li=0.08 Ankle height

13%

87%

L/Li=0.50 Knee height

49%

51%

L/Li=75 Crotch height

33%

67%

L/Li=0.95 Waist height

10%

90%

CEP - US BOX

25%

75%

STEEL BOX

88%

12%

Table 2 demonstrates the significantly better intrinsic shielding provided by the CEP - US packagings compared with steel. The spherical shape of the package contents in the CEP - US Cube causes the side wall thickness to vary. At the bottom and the top of the Cube the concrete is quite thick and essentially all of the radiation is absorbed in the concrete wall. The concrete is thinnest midway up the side (L/Li=0.5). Here the wall absorbs 51% of the radiation. Three-fourths the way up the CEP - US Cube wall the concrete thickness shields out 67% of the radiation. The wall of the CEP - US Box shields out 75% of the radiation. The wall of the Steel Box shields out only 12% of the radiation. These numbers demonstrate the potential to reduce personnel exposure by a factor of about 6 (i.e., 75/12) by using concrete packagings instead of steel for radioactive waste material. If workers are now receiving 200 mR/year from handling radioactive waste boxes this would be reduced to about 33 mR/year if concrete boxes were substituted for steel. This would reduce the worker radiation exposure by 25% during the first year.

D.      Dimensional Characteristics of CEP - US Reinforced Concrete Radwaste Packages.

These dimensional characteristics of the two CEP - US packaging designs are compared with other typical packages in the table below.

TABLE 3. DIMENSIONAL COMPARISON OF TYPICAL RADIOACTIVE WASTE PACKAGES.

PACKAGES

INTERNAL VOLUME, CU. FT.

MAXIMUM CONTENTS, LB.

MAXIMUM OPENING, INCH

CEP - US CUBE

10.9

1,628

11.8 DIA

CEP - US BOX

60.75

12,000

42x90

STEEL BOX

120.8

6,120

48x90

WOOD BOX

112

2,500

48x84

DRUM, 55 GAL

7.6

1,000

22.5 DIA

This table clearly shows that the CEP - US Cube provides more volume for the waste material and can accommodate heavier package contents than a 55-gallon drum. The CEP - US BOX can carry about twice the amount of heavy weight as the steel box. Thus, the CEP - US packagings can be used more easily and efficiently for most radioactive waste products for waste storage and disposal.

E.      Costs of CEP - US Reinforced Concrete and other Radwaste Packages.

TABLE 4. COST COMPARISON OF RADIOACTIVE WASTE PACKAGES *

PACKAGE

ESTIMATED COSTS FOR A PACKAGE, $

ESTIMATED COSTS PER CU. FT., $

ESTIMATED COSTS PER LB., $

CEP - US CUBE

1,000

92.00

0.61

CEP - US BOX

8,000

92.00

0.67

STEEL BOX  (Qualified for transport)

7,500

62.00

1.23

STEEL BOX

3,750

31.00

Approx. 1.00

* Because of the very short lifetime of buried wooden boxes and the stacking instability of metal drums for storage these two package types are excluded from this table.

This tabulation shows that the initial costs of metal and concrete packagings are the same. For lightweight waste, where the container contents are limited by the volume capacity of the package, the steel box has a cost advantage but for more dense materials the concrete packagings have a very distinct cost advantage. Combining the results from tables 2, 3 and 4 clearly demonstrates that for the same packaging costs it is possible to use a concrete package which has a lifetime that is at least ten times longer than a metal box. Any retrieval and repackaging associated with metal packages clearly make them inordinately more expensive than concrete packagings.

F.       Stacking Stability of CEP - US Reinforced Concrete Radwaste Packages.

The CEP - US concrete packaging design assures stacking stability with no voids between stacked packages. The CEP - US Box has a very flat top and bottom with a 4' by 8’ footprint. The major design features are shown in Figure 1. The basic rectangular shape of the box has been modified by filling in the corners to provide structural rigidity to withstand the drop test requirements. The open top of the box is slightly smaller than the lid so it will accommodate decommissioning debris. There are 4 crane attachment points on the lid. Only 3 of the 4 attachment points on the box are visible in this view. Several features have been incorporated into the design of the Cube to provide outstanding handling and stability. These are shown in Figure 2. Inherent in this design is the nesting feature where the upper Cube in a stack has a protrusion on its bottom, which fits into a recess on the CEP - US Cube immediately below. A protrusion on the left side of the cube fits into a recess in the cube immediately adjacent on its left. Similarly, the protrusion on the front of the cube fits into a recess in the cube immediately in front of it. In this manner each cube is locked into place in the three orthogonal directions providing a high degree of stability and permitting stacking to great heights, if desired. The structural capacity of the Cube permits stacking 100 cubes high. The design of CEP - US packagings minimizes voids within the stored waste packages and eliminates any concern about subsidence of the over burden during storage or disposal. 

                    FIGURE 1:  CEP - US Box 

                                                       

                                                                                                                                          FIGURE 2:  CEP - US Cube 

G.      Easy Retrieval from Interim Storage of CEP - US  DOT Concrete Radwaste Packages.

The built-in attachment points for crane hooks in the CEP - US packagings permit both easy placement and retrieval of the packages from any interim storage.

SUMMARY.

  1.    CEP - US packagings will last for hundreds or thousands of years compared with probably less than 50 year for steel packagings.

  2.    Using CEP - US DOT concrete packagings instead of steel can reduce radiation exposure to about 1/6 th of its previous value.

  3.    Procurement costs of metal and concrete packagings are the same. Ultimate costs favor concrete.

  4.   The volume and weight capacity of CEP - US packages is equivalent or better than packages now used.

  5.   CEP - US packagings stack securely and easily using built-in crane attachments and are ideal for retrievable interim storage or permanent disposal.

                     

Containment for Environmental Protection - US Inc.