On the application of Monte Carlo methods to problems in neutron and gamma-ray transport theory
The theoretical treatment of the transport of particles and radiation
gives rise to problems of great mathematical complexity. The
standard methods which are presently used to solve the transport
problems that appear in reactor, accelerator, space, and weapons
shielding as well as in medical radiology are often questionable.
Extensive, and not always realistic idealizations have to be made to
achieve numerical solutions even when using the most up-to-date
electronic computing equipment. The first aim of the present thesis
is to indicate the possibility of using Monte Carlo techniques as a
general tool for routine calculations in photon and neutron transport
theory. This has not generally been possible before as Monte Carlo
work required too much of intuition and numerical experimentation
to make the method practically applicable on a broader scale. The
second aim of this thesis is to show, in a number of cases, the possibilities
of constructing simplified mathematical models which give a
satisfactory picture of the physical problem to be solved to permit
approximate results to be obtained by essentially analytic means.
The Monte Carlo methods were used to test the applicability of these
models. The third aim of the present thesis is to give some results
of problems which have not hitherto been satisfactorily solved.
Papers I, II, and III deal with the reflection of gamma radiation,
and Monte Carlo results are compared with results obtained by simplified
computational models. Paper IV gives an account of the Monte
Carlo procedures used in the previous papers and some additional
results of practical interest are shown. In papers V and VI a general
method for deep penetration calculations is outlined and applications
to photon problems are demonstrated. In paper VII the method is
generalized with regard to geometry and applied to neutron penetration
problems. In paper VIII, finally, the approach used for analyzing
deep-penetration problems is shown to be efficient also for reflection
problems. Results are displayed of some neutron back-scattering
problems involving a variety of materials and source energies.