The Chemistry of Fusion Technology: Proceedings of a Symposium on the Role of Chemistry in the Development of Controlled Fusion, an American Chemical Society Symposium, held in Boston, Massachusetts, April 1972

404 Pages·1972·10.14 MB·English

by  William C. Gough (auth.)

THE CHEMISTRY OF
FUSION TECHNOLOGY
THE CHEMISTRY OF
FUSION TECHNOLOGY
Proceedings of a Symposium on the Role of Chemistry in the
Development of Controlled Fusion, an American Chemical
Society Symposium, held in Boston, Massachusetts, April 1972
Edited by
Dieter M. Gruen
Chemistry Division
Argonne National Laboratory
Argonne, Illinois
<±'
PLENUM PRESS • NEW YORK-LONDON • 1972
Library of Congress Catalog Card Number 72-89488
ISBN-13: 978-1-4613-4597-8 e-ISBN-13: 978-1-4613-4595-4
DOl: 10.1007/978-1-4613-4595-4
© 1972 Plenum Press, New York
Softcover reprint of the hardcover 1st edition 1972
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
United Kingdom edition published by Plenum Press, London
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All rights reserved
No part of this publication may be reproduced in any form
without written permission from the publisher
INTRODUCTION
Nuclear energy obtained from thermonuclear fusion of
light nuclei is a goal to which an increasing world-wide
effort is being committed. The demands on energy reserves
and resources are continually increasing as ever more coun
tries achieve modern industrial status. All projections
agree that conventional means of energy production must be
supplemented and indeed supplanted by new methods. Only the
date at which the transition becomes imperative is subject
to debate. The promise of fusion energy ultimately to pro
vide a clean, cheap, dependable and potentially inexhaustible
energy source augurs well for the future of the human race.
If there were illusions at the start of the quest for
controlled thermonuclear power that solutions would be easily
found, the past two decades have dlspelled them. Unwarranted
optimism has been replaced by a realistic recognition of the
immense scientific and technological challenges that arise
in bringing about practical fusion energy. Broadly speaking,
problems can be put into two categories--those having to do
with heating the fuel to thermonuclear temperatures at high
enough particle densities and for sufficiently long confine
ment times to yield a net power return and those having to
do with the actual construction of a power producing fusion
reactor.
Most of the past and present fusion effort is devoted
to the solution of the first set of problems. Indeed this
must be the case at least until the scientific feasibility
of the fusion power concept is demonstrated. However, as
optimism for the eventual success of the project grew in the
last few years, sparked by the outstanding performance of
Tokamak-type devices, the need for a closer examination of
the problems associated with the operation of an actual
fusion reactor has come to be felt ever more strongly. In
response to this need, a number of groups have begun to exa
mine various areas of fusion reactor design, development and
operation. It has become clear that extreme demands will be
placed on materials of construction by the unusual require
ments of the fusion regime. Indeed the fusion program will
be a spur to the development of advanced technology in a
number of different fields. The solutions to the wide
variety of problems that will be encountered require the best
efforts of workers in a number of different disciplines.
v
vi INTRODUCTION
That the role of chemistry in the development of con
trolled fusion will be an important one was demonstrated at
a recent symposium on that topic held at the American Chem
ical Society Meeting in Boston, April 12, 1972 under the
auspices of the Division of Nuclear Chemistry and Technology.
The papers delivered at that symposium are contained in the
present volume.
To those not intlmately familiar with fusion power re
quirements, the mention of chemistry in connection with this
subject may seem a bit strange because the emphasis so far
has been so heavily on the plasma physics aspects of the
problem. This book should serve as a good introductlon to
the various aspects of a fusion reactor that are "chemical"
in nature. A few of the more important chemical problem
areas are touched on in the following paragraphs.
Tritium breeding requires lithium containing blankets
surrounding the pl asma. fJeutroni c and heat transfer studies
indicate that flowing lithium is quite attractive for the
dual role of tritium breeding and heat transfer. But the
chemical problems of hot lithium compatibility with contain
ment materials and the need to electrically insulate flovling
lithium from metal tube walls must be answered before such
a blanket concept is viable. Alternatives, such as noncon
ducting lithium salts, must also be studied in case the
chemical problems with lithium prove insurmountable. No
matter what form blankets take, methods must be developed
to efficiently recover the tritium generated while keeping
the tritium holdup to a miniumum. The helium by-product
must also be removed and collected.
The successful use of any coolant or blanket material
will depend on a very large number of physical and chemical
properties. A number of the important properties of lithium
need to be studied in much more detail than heretofore. For
example, methods for species characterization in molten
lithium and for the analysis, preferably on a continuous
basis, of certain important impurities need to be developed.
The blanket system of a fusion reactor must serve
several functions and will probably be a composite of sever
al materials. Tritium breeding requires a substantial
lithium density. Neutron moderation seems best served by
use of graphite, and a suitable liquid will be required for
INTRODUCTION vii
transfer of heat from the vacuum wall and the blanket region
to the power generation equipment. The liquid should also
be compatible with graphite and with the metallic portions
of the system. Lithium salts which, alone or as major com
ponents in melts, warrant consideration as possible competi
tors for molten lithium metal as the blanket fluid need to
be investigated from the point of view of their possible use
in fusion reactors. Relatively simple consideration shows
certain disadvantages for several molten salt liquids. Di-
1u t i on of tritium by hydrogen seems to eli mi na te Li OH; Li N03-
LiN02 mixtures have relatively poor thermal stability and
graphite would have to be clad if they were used. The rela
tively high absorption cross section of Cl- for intermediate
and low energy neutrons probably relegate LiCl mixtures to
secondary consideration. Lithium fluoride is essentially
inert toward graphite and many metals. This material, whose
lithium density is higher than that of pure lithium, melts
at 848°C. Its mixtures with BeF2, which have been used as
fuel solvents and coolants in molten salt fission reactors,
have good radiation stability, and are adequate heat trans
fer agents. Such mixtures seem, at present, the most likely
molten salt candidates for CFR blanket fluids.
For thermonuclear power reactors based on the contin
uous fusion of deuterium and tritium, the principal fuel
processing problems occur in maintaining desired composi
tions in the primary fuel cycled through the reactor, in the
recovery of tritlum bred in the blanket surrounding the re
actor, and in the prevention of tritium loss to the environ
ment. Since all fuel recycled through the reactor must be
cooled to cryogenic conditions for reinjection into the re
actor, cryogenic superfractionation is a likely process for
removing ash. Another possibility is the permeation of
deuterium and tritium through thin metal membranes. Neither
of these processes is suitable for removing tritium from
the ash discharged from the power system; only chemlcal pro
cedures are practicable. The recovery process for tritium
from the breeder blanket depends on the nature of the blan
ket fluids. For molten lithium the possibilities are
stripping with inert gas or permeation from the liquid phase.
For molten salts the process would involve stripping with
inert gas followed by chemical recovery. In either case
extremely low concentrations of tritium in the melts would
be desirable to maintain low tritium inventories and to min
imize escape of tritium through unwanted permeation. Sub
stantial chemical research effort is needed in this area
viii INTRODUCTION
to recover bred tritium efficiently, to prepare partially
burnt fuel for reinjection and to prevent tritium loss to
the environment.
The permeation of hydrogen isotopes through the walls
of a controlled fusion reactor is a potentially important
problem for various reasons, the primary one being that the
recovery of tritium is essential to the economics and safety
of the system. A detailed evaluation of the problem re
quires more reliable and ext'ensive data than are currently
available on the rate of permeation of hydrogen isotopes
through structural materials of lnterest in fusion reactors
over a representative range of conditions. EXisting and
future experimental data need to be compared with theoreti
cal predictions and correlations. The effects of surface
treatments, radiation damage, and nonidea1 solution behavior
are areas that require further intensive research.
For continued progress leading to economically attrac
tive fusion reactors, the use of large superconducting mag
nets for the heating and confinement of plasmas appears to
be necessary. Similarly, superconducting transmission line
networks will be required for the distribution of power from
large fusion reactors. For each application, the "best"
superconducting material may exhibit different properties.
but for both uses, the search for new and better supercon
ducting materials and fabrication methods will be a contin
uing requirement. Theories of superconductivity are very
successful in explaining properties of the superconducting
state and the origin of superconducting electron pairs. but
up to the present have been of little value in guiding the
search for better superconducting materials. Progress has
been made through the use of empirical correlations of nor
mal state properties with superconducting transition tem
peratures. These include: average number of valence elec
trons per atom versus Tc; valence electron density versus
Tc; lattice parameter of M-M distances (M = transition
metal) versus Tc in special crystal structures; and varia
tions of these approaches with attempts to include lattice
properties. Recent work has demonstrated that stoichiometry
and ordering are most important and that correlations must
be revised through the use of samples that have been char
acterized more completely. The role of chemical research
in the development of better superconducting materials is
becoming more clearly defined. There is no doubt that this
INTRODUCTION ix
is an area where chemical research and chemical insights
can be expected to make major contributlons.
The properties of meta111c and sa11ne hydrldes and
their correspondlng deuterides and tritldes are of consid
erable interest to controlled fusion reactors. The effect
of deuteride and trltlde formatlon on the strength of struc
tural materials under operating condltlons of a reactor, the
solubility of radioactive tritlum ln metals, and the use of
metal hydrldes as shle1d materials, and for hydrogen storage
are topics where chemical research is needed and can be ex
pected to contribute to the solution of important problems.
The thermonuclear plasma consists of deuterium, tritium
and helium. A flux of plasma particles will lnteract with
the vacuum wall of the reactor and, in some designs, with
divertor structures. Deuterium and tritium are "reactive"
substances which can be expected to interact chemlca11y wlth
meta 1 wa 11 s. Vari ous "chemi ca 1" phenomena such as chemi
sorption, "trapping", "chemical" sputtering and hydride
molecule formation are of importance to the operation of a
thermonuclear fuslOn reactor. Many of these phenomena, al
though chemical ln nature, have not hltherto been studled by
chemists. It is clear that in this area also, the inslghts
of the chemist will lead to lncreased understanding of a
series of complex phenomena.
The ramiflcatlons of these various subjects are dis
cussed ln authoritative detail in this volume.
The c1asslca1 approach to controlled thermonuclear
fuslon has been centered on magnetic conflnement of the
plasma. Recently, conslderab1e effort has been dlrected to
an alternate approach, lnertia1 confinement, which makes use
of high power lasers to induce the fUSlon process. For DT
fuels, the chemical problems assoclated with tritlum breed
ing and recovery must be dealt with even in thlS approach.
Furthermore, the development of the ultra hlgh power lasers
required to induce fuslon presents a varlety of lntriguing
chemical problems. The lmportant parameters that must be
met in order to achleve laser induced fuslon are discussed
in the last paper ln this book.
symposium or symposlum proceedlngs can come about
r~o
without the wholehearted and enthusiastic cooperatlon of a
x INTRODUCTION
very large number of people. It has been my good fortune to
have been associated wlth just such a group of people. Ny
thanks for a job well done go flrst of all to the partici
pants in the symposium who with thelr assoclates also
authored the papers. Special thanks are due John Huizenga
for endorsing the organlzation of the symposlum on behalf of
the Divislon of Nuclear Chemlstry and Technology of the
American Chemical Society and to Paul Flelds for his encour
agement of these efforts and his continuing interest. Fin
ally my thanks go to Miss Brenda Grazls for secretarlal
assistance on several aspects of the manuscript.
Dieter M. Gruen
Argonne National Laboratory
August 22, 1972
LIST OF CONTRIBUTORS
Melvin G. Bowman
Los Alamos Scientific Laboratory, Los
Alamos~
New Mexico
Fred A. Cafasso
Chemical Engineering Division, Argonne National
Laboratory, Argonne, Illinois
Elton J. Cairns
Chemical Engineering Division, Argonne National
Laboratory, Argonne, Illinois
Stanley Cantor
Reactor Chemistry Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee
William C. Gough
Division of Controlled Thermonuclear Research
U. S. Atomic Energy Commission, Washington, D. C.
Warren R. Grimes
Reactor Chemistry Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee
Dieter M. Gruen
Argonne National Laboratory, Argonne, Illinois
Ernest F. Johnson
Department of Chemical Engineering and Plasma
Physics Laboratory, Princeton University, Princeton,
New Jersey
Joseph D. Lee
Lawrence Livermore Laboratory, University of Cal
ifornia, Livermore, California
xi