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Regional Basic Professional Training Course in Korea

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<strong>Regional</strong> <strong>Basic</strong> <strong>Professional</strong> <strong>Tra<strong>in</strong><strong>in</strong>g</strong> <strong>Course</strong> (BPTC) on Nuclear Safety<br />

probability of <strong>in</strong>teraction.<br />

FIG. 1.7. A beam of I particles per cm 2 knock<strong>in</strong>g a very th<strong>in</strong> target conta<strong>in</strong><strong>in</strong>g N nuclei per cm 3<br />

S<strong>in</strong>ce neutrons are not electrically charged, they are the most suitable projectiles to<br />

<strong>in</strong>teract with nuclei and this could be done even at zero k<strong>in</strong>etic energy (there is no<br />

required energy to overcome electrostatic barrier). There are different types of<br />

neutron-nucleus <strong>in</strong>teractions. We usually dist<strong>in</strong>guish between scatter<strong>in</strong>g and absorption<br />

reactions. In the scatter<strong>in</strong>g process, one neutron is available <strong>in</strong> the exit channel while <strong>in</strong><br />

absorption processes we usually do not f<strong>in</strong>d neutrons. The follow<strong>in</strong>g schematic diagram<br />

gives a non-exhaustive list of possible reactions.<br />

Scatter<strong>in</strong>g Elastic (n, n)<br />

Inelastic (n,n')<br />

Absorption Fission<br />

Capture (n, γ ), (n, p), (n, α ),L<br />

As for the probability of neutron-nucleus <strong>in</strong>teraction, we can def<strong>in</strong>e a cross-sectionof<br />

each <strong>in</strong>dividual reaction. We then speak about scatter<strong>in</strong>g cross-section, absorption cross<br />

sections…As these <strong>in</strong>teractions are <strong>in</strong>dependent from each other, the probability of total<br />

<strong>in</strong>teraction is just the sum of partial cross sections:<br />

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