Title:

A Study of Neutron Heating in Fusion Reactor Materials.

An important. quarrti,ty iD the design and analysis of corrtrIoLed
thermonuclear reactor._s. is the rate of heating in the material of
the breeder bIenke t , due ·to'nuclear interactions induced. by neutrons
originating in the fusion plasma. This 'nuclear heating' consists
of three parts: neutron heating, gamma heating and a,ctiva,tionheating.
In this work a method is developed for the calculation of neutron
heating rates, utilizing computer codes uhich are already in common
use for fusion reactor neutronics calcu,.lations,and using nuclear
data which is also readily available; mainly that data uhich is
.e.Lreadyin use for the computet Lon of neutron fluxes.
The introduction, chapter 1, reviews the principles of controlled
thermonuclear ree.tccrs, and conceptual designs for the .maLn types of
reactors that have been proposed, 'Hith particula.r emphasis on the
effects of the various designs on the neutronics of the breeder blanket
region. The importance of neutron heating calculations is also
discussed.
In chapter 2, calculational methods used for estimates of neutron
fluxes are reviewed, in particular the method of discrete ordin~.tes,
as used in this 110rk. Data requirements of these cc:lculations arc
discussed, and previously used methods for neutron heating calculations
revie.. red.
The theory 01' the present method for neutron heating calculations
are presented in chapter 3. Equations are developed for the energy
depositj,on in each principle neutron reaction type, and these are
combined to give a general formula for total neutron energy deposition It is shown tha t any reaction type (except fission) can 'be
represented by this equation.
Ohap'ter 4 di acuase s the total energy rel ee.sed in inelastic
scattering events, and a'method for calculeting this is developed,
for use in the equations of chapter 3. This method makes use of
known energy levels in the nuclei of interest, end an evapora t i on
model approximation for the continuum of higher energy levels.
The results of chapter 3 are put :i,nto a form suitable for
calculation in chapter 5. Averaging into energy multigroups is
. discussed, and an eque.ti on for the multigroup energy deposi tion
factors is developed. The use of these factors is described, vnd..
finally en alternative method for neutron heat Lng celcu~:;'tions, by
overel l energy balance considerations, is outlined.
The method developed in chapte r s 3  5 is applied in chc.pte r 6
to calculations of neut ron heat.Lng re.te s in a varLety of materials
of interest in fusion rea.ctor design. These cs.Lcul.ations are
perf'ormed 'both in simple slab configurations and in a simple fusion
reactor blc:.nket design. Calculations of neutron heating by a
previous method are also made for comperison purposes, and agreement
is good in most regions. As a further check, the alternative method
outlined at tile end of chapter 5 is e.Lso applied, and agreemerrt is
again good.
Chapter 7 turns to. an exe.minadiianof activetion heating rates
in the seme fusion reactor b'Lanket design C.s used in chapte r 6.
Activat.ion heating rc.t es , which aro found to be small compared'With
!
neutron heating rates, are presented both as a f'unct i.on of position and of time.
Conclusions are made in chapter 8, ..There a f'Low die>gre.mof the
·va.:rious computing mc\hods and programsinvolved is used to display
the features of the different methods, end the advantages of the
present method.
A description of the use of the program ENBAL, ..rhd ch uses the
methods for neutron heating developed in chapters 3  5, is provided
in the appendix.
