Quality Factors for Neutrons

DOE-STD-1128-98

Table 6.8. Nuetron Yields from Alpha-Neutron Reactions for Oxides and Fluorides

Average Alpha α , n Yield in

α , n Yield in

Alpha

Decay

Yield

Energy

Oxides

Fluorides

α /s-g

Isotope

Half-Life

MeV

n/s-g

232Th

1.41 x 1010 y 4.1 x 103

4.00

2.2 x 10-5

232U

71.7 y

8.0 x 1011

5.30

1.49 x 104

2.6 x 106

233U

1.59 x 105 y

3.5 x 108

4.82

4.8

7.0 x 102

2.45 x 105 y

2.3 x 108

4.76

3.0

5.8 x 102

234

235U

7.04 x 108 y

7.9 x 104

4.40

7.1 x 10-4

0.08

236U

2.34 x 107 y

2.3 x 106

4.48

2.4 x 10-2

2.9

238U

4.47 x 109 y

1.2 x 104

4.19

8.3 x 10-5

0.028

237Np

2.14 x 106 y

2.6 x 107

4.77

3.4 x 10-1

238Pu

87.74 y

6.4 x 1011

5.49

1.34 x 104

2.2 x 106

239Pu

2.41 x 104 y

2.3 x 109

5.1

3.81 x 101

5.6 x 103

240Pu

6.56 x 103 y

8.4 x 109

5.15

1.41 x 102

2.1 x 104

241Pu

5.90 x 105 y

9.4 x 107

4.89

1.3

1.7 x 102

242Pu

3.76 x 105 y

1.4 x 108

4.90

2.0

2.7 x 102

241Am

433.6 y

1.3 x 1011

5.48

2.69 x 103

242Cm

163 days

1.2 x 1014

6.10

3.76 x 106

244Cm

18.1 y

3.0 x 1012

5.80

7.73 x 104

249Bk

6.6 x 104 y

8.8 x 108

5.40

1.8 x 101

252Cf

2.646 y

1.9 x

1013

6.11

6.0 x 105

Multiplying the specific neutron yield (neutrons/second-gram of

plutonium) by the mass of plutonium (grams) gives S, the neutron

emission rate (neutrons/second). The dose equivalent rate is then

calculated using Equation 6.4.

6.2.3.3 Quality Factors for Neutrons

Approved Quality factors for neutrons are provided in 10 CFR 835.2. As

used here Quality Factor means the principal modifying factor used to

calculate the dose equivalent from the absorbed dose; the absorbed dose

(expressed in rad or gray) is multiplied by the appropriate quality factor

(Q).

6-17