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Page Title:
Table 2.4. Specific Activity Decay Heats of Selected Isotopes(a) |
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| 0033im.jpg) DOE-STD-1128-98
Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities
Table 2.4. Specific Activity Decay Heats of Selected Isotopes(a)
Average Particle Energy per
Half-Life,
Specific Activity, Ci/G
Decay Heat,
MeV(b)
W/g(b)
Isotope
y
"
"
236
Pu
2.851
534
5.75
18.2
"
"
238
Pu
87.7
17.1
5.49
0.567
"
"
239
2.407 x 104
6.22 x 10-2
1.93 x 10-3
Pu
5.14
"
"
7.13 x 10-3
240
Pu
6564
0.229
5.16
"
"+$ 5.27 x 10-3
2.52 x 10-3
3.29 x 10-3
241
Pu
14.35
$
103
"
"
242
3.733 x 105
3.93 x 10-3
1.16 x 10-4
Pu
4.90
"
"
232
U
72.0
21.5
5.31
0.690
"
"
233
1.59 x 105
9.75 x 10-3
2.84 x 10-4
U
4.72
"
"
2.45 x 105
6.29 x 10-3
1.81 x 10-4
234
U
4.76
"
"
7.04 x 107
2.17 x 10-6
6.02 x 10-6
235
U
4.24
"
"
2.34 x 107
6.5 x 10-5
1.77 x 10-6
236
U
4.48
"
"
4.47 x 109
3.38 x 10-7
8.58 x 10-9
238
U
4.18
"
"
2.14 x 106
7.08 x 10-4
2.08 x 10-5
237
Np
4.76
"
"
241
Am
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.
2-7
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