A source of generic information

The chart is helpful when tracking down unknown radionuclides detected in a measurement to know what type of nuclear reaction may have been responsible for the production of the activity. In most cases, this will be a thermal neutron reaction resulting in activation by (n, 7), or if the target material is fissile, a fission reaction (n, f). 

If this is the reaction, then the search for nuclides is narrowed dramatically. From more than 2000 radionuclides displayed on the chart, we need scan only 180 or so. It is clear that as the (n, 7) reaction merely adds one neutron to a stable nuclide we must look at isotopes just one square to the right of a (black) stable one. For example, instead of considering all 21 radioisotopes of arsenic, we need look at only one the stable arsenic is As and therefore we look at As. There are just two qualifications to this simple picture  

This is due to the very large neutron absorption cross-section of the first product, Au. In most cases, while there may be a considerable amount of activity formed by an (n, 7) reaction, this will correspond to relatively few atoms. Thus, the amount of target material available for a second reaction is small, and a large reaction probability (as we have here with Au) is needed to give significant amounts of the second reaction product. The second complication is when the (n, 7) product does not decay to a stable nuclide hut to a radioactive one. Then nuclides that are an extra transformation away (3 normally) need to he considered. An example is  

A further point most elements have more than one stable isotope. So, if one activation product is found, check with the chart for others that could be formed by the same mechanism. For example, if 35.3 h Br is seen, formed by (n, 7) from stable Br, look at the chart which wiU tell you that there is plenty of stable Br with an 

With U(n, f) the distribution peaks at A = 90 to 100, and A = 134 to 144. The cumulative fission yield data for each mass number are given on the Karlsruhe Chart as percentage ydelds on the right-hand edge of the chart. 

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