Page 177 - Radiochemistry and nuclear chemistry

Absorption of Nuclear Radiation 161

water-containing materials. In an instrument using 10 mCi 9~ the hydrogen concentration
in a 10 ml sample can be determined in 20 rain with 0.03 % accuracy. This is not only
superior to other conventional analytical methods, it also has the advantage of being a
nondestructive technique.
Neutrons are slowed down most effectively by light elements (w As a consequence,
neutron scattering can be used for the analyses of light elements, particularly hydrogen. In
one type of instrument the radiation source consists of 252Cf which produces fast neutrons
(from spontaneous fission), while the detector is sensitive only to slow neutrons. This
system is used for studies of ground water and analysis of bore holes in wells (Fig. 6.29,
G). These analyses are usually combined with density determinations using a 3~-source,
thereby making it possible to identify strata of water, oil, coal, etc.
Some properties and uses of commercial radionuclide gauges are listed in Table 6.4.

6.9.2. Radiography

Radiography is a photographic technique in which nuclear radiation is used instead of
light. Medical examination and nondestructive industrial testing using X-rays generated by
high-vacuum tubes are the most important areas. A number of suitable sources of
radioactive nuclides for producing radiograms are given in Table 6.4.
Beta-radiography is only suitable for thin objects and not widely applied. On the other
hand, -y-radiography is a common nondestructive test technique in which normally 137Cs
or 6~ has been used. v-radiography has advantages in field use and in detection of
sensitive objects. The radiation source can be 6~ which is normally kept in a portable
radiation shielding of 30-60 kg of lead and situated at the end of a rod so that it can be
pushed out of the shielding for use. The photographic film is located in a cassette
surrounded by amplifying screens.

TABLE 6.4. Some commercially available radionuclide gauges and 3"-sources for
radiography (France)

Radiation Source t,,~ Application

o~ U or Ra Long Thickness control in manufacturing paper, aluminum;
<_ 60 g/m 2
Soft/3 147pm(0.2 MeV) 2.6 y Thickness control; _< 400 g/m 2
/~, soR 3' :S~l'l(0.8 MeV) 3.8 y Thickness: 1.10 mm steel, 3-50 mm glass; 8-100
kg/m 2
Hard/3 144Ce(3 MeV) 0.78 y Thickness ___ 1 mm steel; < 10 kg/m 2
X 1~ keV) 1.24 y Detection of S-content in hydrocarbons
n,3' RaBe, 137Cs 30 y Moisture-density meter for civil engineering and
agriculture
3' e~ MeV) 5.3 y 4 MBq source for backscatter on _< 20 mm steel,
0.4 - 40 GBq for remote level indication
SoR 3' t921r(0.3 MeV) 74 d 400 GBq, 26 kg: < 40 mm steel radiography
Medium 3' 137Cs(0.7 MeV) 30 y 400 GBq, 45 kg: _<_ 70 mm steel pipeline inspection
Hard 3' ~~ MeV) 5.3 y 10 TBq, 900 kg: < 180 mm steel radiography