TNAG-1508-FCO40-2066-Guangdong-nuclear-power-station-project-at-Daya-Bay-safety-c-1987 — Page 49

maximum allowed density.

That is why the beer of China is

praised internationally as the "clean beer".

Nuclear reaction analysis? In the course of nuclear reaction

between the ion-beam and the substance, the measurement of the

characteristics of the emitted particles or the energy of the

Y-rays with a view to ascertaining the composition of the sub-

stance and the depth distribution of the impurity elements on

the surface of a solid is called nuclear reaction analysis.

It has the following merits: high selectivity, high sensitivity,

high precision, non-destructiveness and high speed. It is

suitable for analyzing the light foreign elements in heavy

host-material, such as H, B, C, N, O,F, P, etc; applicable in ion

injection, matérial science, surface physics and surface

chemistry. To put it more concretely, it can be applied in the

polishing process, surface treating, corrosion, as well as the

oxygenization, nitriding and hydrogenization on the surface of

various metals in the field of metallurgical research. In thin-

film technology, this analysis method can find its applications in

thin-film growth, vacuum sedimentation, sputtering mechanism,

purity, trace contamination, as well as the research into the

migration of the various impurities such as sodium and fluorine

under high temperature. For example, in the analysis on the

hydrogen-melting monocrystal silicon, it has been detected that

the depth distribution of hydrogen is 1/1000, and its surface

distribution is 2 x 10

1016/cm2; this is hard to be achieved by

other methods.

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