Panasonic PT-DZ12000U Operating Instructions Manual page 176

RULES OF THUMB FOR NEUTRONS
1. The number of neutrons per square centimeter per second
at distance R from a small source emitting Q neutrons per
second without shielding is given by;
n / cm -sec = Q / 4 R
2. For á, ç sources use the following equation to approximate
the number of neutrons per second per Ci (Q).
Q = 5.6E3 x (alpha particle energy in MeV)
This holds true for Be; multiply by 0.16 for B targets, by 0.05
for F, by 0.015 for Li, and 0.003 for O targets.
3. For neutron energies from 1 to 10 MeV the neutron
exposure rate is approximately equal to 1 mrem/hr at 1
meter for each 1E6 neutrons per second emission rate.
Multiply the neutron mrem/hr at 1 meter by 11.1 to calculate
the neutron exposure rate for the same source at a distance
of 30 cm.
4. For spontaneous fission the gamma exposure rate for an
unshielded source is approximately twice the neutron
exposure rate.
5. The range of neutrons in air for energies from 0 to 10 MeV
is from a few centimeters to 100 meters.
6. The range of neutrons in water (or tissue) for energies from
0 to 10 MeV is from a few millimeters to 1 meter.
7. Neutron flux to dose rate conversion:
Fast:
Slow:
2
1 mrem (0.01 mSv) / hr per 6 n / cm -sec
1 mrem (0.01 mSv) / hr per 272 n / cm -sec
2
= 0.08Q / R
2
3.65
2
2