Reaction Rates - h1019v1

REACTION RATES - h1019v1_122

Reactor Power Calculation

Nuclear Physics and Reactor Theory Volume 1 of 2
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R_f f 1 x 10¹³ neutrons cm² sec 0.1 cm¹ 1 x 10¹² fissions cm³ sec R_f f f R_f 1.29 x 10¹² fissions cm³ sec 3 x 10¹³ neutrons cm² sec 0.043 cm¹ Reactor Theory (Neutron Characteristics) DOE-HDBK-1019/1-93 REACTION RATES Rev. 0 Page 19 NP-02 The reaction rate calculated will depend on which macroscopic cross section is used in the calculation. Normally, the reaction rate of greatest interest is the fission reaction rate. Example: If a one cubic centimeter section of a reactor has a macroscopic fission cross section of 0.1 cm , and if the thermal neutron flux is 10 neutrons/cm -sec, what is the fission rate -1 13 2 in that cubic centimeter? Solution: In addition to using Equation (2-6) to determine the reaction rate based on the physical properties of material, it is also possible to algebraically manipulate the equation to determine physical properties if the reaction rate is known. Example: A reactor operating at a flux level of 3 x 10 neutrons/cm -sec contains 10 atoms of 13 2 20 uranium-235 per cm . The reaction rate is 1.29 x 10 fission/cm . Calculate and . 3 12 3 f f Solution: Step 1: The macroscopic cross section can be determined by solving Equation (2-6) for and substituting the appropriate values. f

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