NEUTRON LIFE CYCLEDOE-HDBK-1019/2-93Reactor Theory (Nuclear Parameters)The next step in the analysis is to consider the number of neutrons that are absorbed in theintermediate energy level. The probability of escaping this resonance absorption (p) is statedas follows.p number of neutrons that reach thermal energynumber of fast neutrons that start to slow down7209000.80The number of neutrons entering the thermal energy range is now represented by the quantityNo fp.After reaching thermal energies, 100 neutrons leak from the core. The value for tcan becalculated by substitution of the known values in the definition as shown below.t number of thermal neutrons that do not leak from reactornumber of neutrons that reach thermal energies6207200.861The number of thermal neutrons available for absorption anywhere in the core is represented bythe quantity No fp t.Figure 1 indicates that 125 neutrons were absorbed in non-fuel materials. Since a total of 620thermal neutrons were absorbed, the number absorbed by the fuel equals 620 - 125 = 495.Therefore, the thermal utilization factor can be calculated as follows.f number of thermal neutrons absorbed in the fuelnumber of thermal neutrons absorbed in any reactor material4956200.799NP-03Rev. 0Page 12
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business