TABLE 5-1 Comparison of Cesium-137 Irradiators

 

Model

Specification

Nordion

GC 1000 Elite

Nordion

GC 3000

CIS

IBL 437C

Shepherd

143

Load (kg/sq m)

1,467

1,886

5,200

Not available

Weight (kg)

1,150

1,479

2,150

907 or 1,814

Height (m)

1.55

1.55

1.50

2

Width (m)

0.8

0.8

0.67

0.6

Depth (m)

0.98

0.98

0.650

0.6

Outlet (V)

110

110

100–240

110

Activity (TBq) [Ci]

24.1–107.4 [575–2,900]

53.7 or 107.4 [1,450 or 2,900]

63–189 [1,700-5,100]

42.8–259 [1,155–7,000]

Canister (liters)

0.824

2.34

3.8

0.6–3.9

Time to deliver 25 Gy (min)

1.6–7.14

2.56–5

2.8 or more

Not available

SOURCE: Courtesy of Gammacell® 1000 Elite/3000 Elan (MDS Nordion, 2006); CIS IBL 437C (CIS-US, Inc., 2007); Shepherd 143 adapted from Cook (1996), with additional information from the Sealed Source and Device Registry.

An example of a dose map of one canister is given in Figure 5-4. If the dose at the midplane is defined as 100 percent, the dose in any portion of the canister other than the very top and bottom center portion does not typically vary by more than ±20 percent. Exposure times are typically several minutes; irradiators containing higher activity sources have shorter exposure times due to their increased dose rate. An irradiator takes twice as long to deliver a given exposure after the source has decayed through one half-life. Given the 30.2-year half-life of cesium-137, a typical blood irradiator is in service for approximately 30 years before needing to reload the source, or more commonly replace the entire irradiator to maintain a practical exposure time. Because blood irradiators are self-contained (they have built-in shielding), they need not be located in a bunker in the basement of a hospital or blood center. The weights of cesium blood irradiators do, however, require more support than is found in the upper floors of many buildings, in which case the irradiators may need to be located next to a structural support for the building or have additional support installed to spread out the weight.

REPLACEMENTS FOR BLOOD IRRADIATORS

There are several alternatives to radioactive cesium chloride self-contained irradiators. These include different material forms for cesium-137 sources, cobalt-60 sources, x-ray sources, chemical inactivation, and filtration techniques. Each of these is discussed below. The committee spoke with the major self-contained-irradiator manufacturers and found them reluctant to shift toward replacements for radionuclide radiation sources without some incentives.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement