## Archive for the ‘Fisica del Reattore nucleare’ Category

### Fuel burn up

venerdì, Aprile 9th, 2021

Appunti ed esercizi di Fisica del Reattore nucleare elaborati dell'ing. Giorgio Bertucelli.

A nuclear fission supplies an average total energy of about 200MeV , a useful nember to remember. The complete fission of 1g of U235 thus produces a quantity of energy equal to

This relates to fuel burn up. Maximum theoretical burn up would therefore be

This figure applies only if the fuel were entirely composed of fissionable nuclei (U235, Pu239, U²³³) and if these nuclei were all fissioned. Reactor fuel, however, contains other uranium or thorium isotopes. Also, the fissionable isotopes in it cannot be all fissioned because of absorbtion stopping the chain reaction. The meaning of fuel is all uranium, plutonium and thorium isotopes; it does not include alloying or other chemical compouns or mixtures. The term used fuel material is to refer to fuel plus other materials.
(altro…)

### Percentage change in mass of the reactants when carbon burns completely in oxygen to CO

domenica, Marzo 21st, 2021

Appunti ed esercizi di Fisica del Reattore nucleare elaborati dell'ing. Giorgio Bertucelli.

Calculate the percentage change in mass of the reactants when carbon burns completely in oxygen to CO2 . The eating value of C is 141000 Btu/lbm=32794kJ /kg .

Solution
The chemical reaction

is exothermic reaction. It should be pointed out here that chemical reactions, like nuclear reactions, are either exothermic or endothermic. That is, they either release or absorb energy. Since energy and mass are convertible according to Einstein's law

chemical reactions do undergo changes in mass, (a mass decrease in exothermic reactions, mass increase in endothermic ones), just as nuclear reactions do. However the quantities of energy resulting from chemical reactions are small compared with those in nuclear reactions, and the fraction of mass of the reactants either lost or gained is extremely small. This is why we assume a preservation of mass in chemical reactions.