Table 2.4. Specific Activity Decay Heats of Selected Isotopes(a)

DOE-STD-1128-98

Table 2.4. Specific Activity Decay Heats of Selected Isotopes(a)

Isoptope

Half-Life

Specific Activity, Ci/G

Average Particle Energy

Decay Heat

per Disintegration, MeV(b)

W/g(b)

2.851

53.4

5.75

18.2

236

87.7

17.1

5.49

0.567

238

239Pu

2.407 x 104

6.22 x 10-2

5.14

1.93 x 10-3

240Pu

6564

0.229

5.16

7.13 x 10-3

α+β

241Pu

14.35

2.52 x 10-3

5.27 x 10-3

3.29 x 10-3

103

3.733 x 105 α

3.93 x 10-3

4.90

1.16 x 10-4

242

232U

72.0

21.5

5.31

0.690

1.59 x 105 α

233U

9.75 x 10-3

4.72

2.84 x 10-4

2.45 x 105 α

234U

6.29 x 10-3

4.76

1.81 x 10-4

7.04 x 108 α

235U

2.17x10-6

4.24

6.02 x 10-8

2.34 x 107 α

236U

6.5 x 10-5

4.48

1.77 x 10-6

4.47 x 109 α

238U

3.38 x 10-7

4.18

8.58 x 10-9

2.14 x 106 α

237Np

7.08 x 10-4

4.76

2.08 x 10-5

241Am

432.2

3.43

5.37

0.115

(a) Data from ICRP 38 (1983).

(b) Includes atomic recoil and low-energy X-ray production.

and decay heats for selected isotopes and decay products are given in Table

2.4. Kilogram quantities of 239Pu or gram quantities of 238Pu can generate

enough heat to melt plastic bags. Sources of 238Pu must be handled with

insulated gloves, and special precautions must be taken to ensure a good

thermal heat sink during shipping and storage. (See also Section 2.5.1, "Self-

Heating.")

The plutonium isotopes emit relatively few high-energy gamma rays, so even

kilogram quantities can be processed without serious gamma-exposure

problems. Because of the high density of plutonium, many gamma rays are

self-absorbed. In some instances, the decay products may become significant in

radiation protection and metallurgy. For instance, the isotope 236Pu often

constitutes less than 1% of plutonium and is often ignored in dose calculations.

However, if the plutonium is shielded by greater than 1 cm of lead or steel, the

decay products of 236Pu may be the largest contributors to exposure. The decay

product 208Tl emits a highly penetrating gamma ray with an energy of 2.615

MeV. In plutonium that contains a few weight percent 241Pu, the 241Am decay

product is important because it emits a large number of 60-keV photons, which

can be a significant source of exposure to the hands and forearms when

handling plutonium in gloveboxes.

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