Thursday, January 15, 2009

Blankets for Thermonuclear Reactors

One of my father's papers has just gone up on the Internet.
Contract No. W-7405-eng-26
C. J. Barton and R. A. Strehlow

Issued June 27, 1962
Achievement of controlled thermonuclear power requires the solution of the very difficult problem of confining a stable energetic plasma. Concentration of research effort on this problem has resulted in little consideration of questions relating to energy extraction from a stable contained plasma. Many uncertainties exist regarding the design of a successful thermonuclear reactor but the fact remains that some fraction of the energy of thermonuclear neutrons must be removed or recovered as heat. Although this consideration alone makes necessary the presence of a heat recovery or removal blanket surrounding the reactor, the production of tritium is an equally necessary function of the blanket for a deuterium-tritium fueled (D-T) reactor. It is also essential that the highly energetic neutrons be prevented from damaging magnetic coil materials such as copper or sodium. The utilization of low-temperature superconducting coils will not, in itself, reduce the need for shielding. This report contains a brief discussion of thermonuclear reactions from the standpoint of energy recovery, a review of various blanket systems which have been suggested for use with thermonuclear reactors, some comments on problems connected with each type of blanket, and some suggestions for research on the blanket system presently considered most promising.

Existing information indicates that molten LiF-BeF2 is a promising blanket material for removing energy from a thernonuclear reactor in the form of useful heat and for breeding tritium. It is also apparent that, in the interest of minimizing blanket thickness and of maximizing neutron multiplication, the possibility of including heavier elements such as lead, tin, barium, and zirconium in a fluoride salt mixture to be placed in one region of a blanket assembly should be considered. It is probably not too early to start to obtain information needed to determine the feasibility of employing molten fluorides in a thermonuclear reactor blanket. Some of the problems that need to be examined are: compatibility of molten fluorides with container and neutron multiplying materials and means of dealing with the corrosion problem resulting from charge imbalance accompanying tritium production, and solubility of tritium and tritium fluoride in molten LiF-BeF2. Due to lack of information on the configuration of a successful thermonuclear reactor, it seems obvious that it wauld not be profitable to attempt blanket design studies at the present time.

Note: My father did not open the door to thorium breeding in the blanket, but that would probably exceeded the expectation for the report. Clearly the door is cracked open, however.

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