# Accession Number:

## ADA156593

# Title:

## The Development of a Neutron Evaporation Theory Code for the Thermal Fission of Uranium-235

# Descriptive Note:

## Final rept.

# Corporate Author:

## ARMY MILITARY PERSONNEL CENTER ALEXANDRIA VA

# Personal Author(s):

# Report Date:

## 1985-05-03

# Pagination or Media Count:

## 115.0

# Abstract:

The thermal fission of Uranium-235 has been studied by developing a computer code that used evaporation theory based on the Weisskopf model for neutron emission from individual fission fragments. This computer code calculates a prompt neutron spectrum for the thermal fission of Uranium-235, calculates the total gamma ray energy for the fission of Uranium-235, and calculates the average prompt neutron kinetic energy. Until now, evaporation theory codes used average values of mass and energy in determining prompt neutron spectra, and this code was developed to use all possible fission fragment combinations in order to eliminate this averaging. This approach is necessary to compute certain measured data such as the probability that 0,1,2,.. . neutrons are emitted per fission. This code uses subroutines to calculate rest masses, corrects the calculated rest mass to agree with experiment, and to determine the emitted neutron kinetic energies. Evaporation theory codes have predicted low total gamma energy release in fission, but agree quite favorably with experiments in predicting the average prompt neutron kinetic energy. The prompt neutron spectrum obtained in this code has a high tail region, that is, below 0.5 MeV. The average kinetic energy of the neutrons agree very well with experiment, and the total gamma energy is lower than experiment, as previous evaporation theory codes have been. Keywords Fission Prompt neutron spectrum Uranium-235, Liquid drop model Semi-empirical mass formula. Theses

# Descriptors:

# Subject Categories:

- Nuclear Physics and Elementary Particle Physics