Chain-reacting system

FIG. 19.4. Neutron spectra of some chain reacting systems and a proposed accelerator driven system. The abscissa shows neutron flux times energy on an arbitrary scale. 

It should be observed that the neutrons lost firom the core are caught by the blanket. C is higher than in any other known chain-reacting system. 

The most significant papers are reproduced in their entirety. Preliminary versions of the papers, numerical calculations of specific chain-reacting systems, or brief notes, are quoted by title and axe designated with the letter T. Copies of these reports are on file at ORNL. 

A chain reacting system will be thermally stable if it becomes less chain reacting as the temperature increases. On the other hand, if the system becomes more chain reacting as the temperature increases, it is thermally unstable. These possibilities have been described already above, by Fermi. 

Every chain reacting system has a critical size . For instance, a heterogeneous U-D2O system cannot be made chain reacting (without a reflector) with less than about 5 tons of D2O and 2 tons of U, a homogeneous U-D2O system with less than about 30 tons of D2O and about 7 tons of U. For a unit which develops power, the requirements increase for three reasons ... 

As a result of the chain reaction, when U is present (as in natural uranium), transuranic element 9423 , known as plutonium, is produced. This material is fissionable and is valuable when added to natural uranium for use in a chain reacting system, as a fissionable body in lieu of or conjunction with natural uranium. 

This strong absoring action of some elements renders a self-sustaining chain reacting system capable of control. By introducing neutron absorbing elements in the form of rods or sheets into the interior of the system for... 

Inasmuch as the reproduction ratio in any self-sustaining chain reacting system is reduced by the presence of impurities that absorb neutrons, such impurities can be introduced into the active portion of the structure in the... 

The metal from the center of the reactor in a system operating at a high power output, for example, at a 9433 concentration of 1 to 2,000, if not cooled, can increase in temperature at the rate of about 2000 C. per hour one day after the neutron activity of the system has been shut down. After 30 days shut down following an operation of 100 days at an output of 500,000 Wlowatts, the average temperature rise can be approximately 572 C. per hour. The uranium metal of the type used in the chain reacting systems herein under consideration melts at about 1100 C. 

The power plant above described is ideally adapted 50 for automatic control to maintain the neutron density within the reactor substantially constant, and thus give a substantially constant power output. Due to the fact that large masses of materials are utilized in the reacting portion of the structure, there is a temperature lag 55 therein. Consequently, it is convenient to monitor and control the structure by means of ionization chambers, or equivalent devices which will measure the neutron density at the periphery of the lattice portion of the structure. As the rate of neutron diffusion out of a 80 chain reacting system is always proportional to the rate of generation of neutrons within the structure, the ionization chambers can readily be placed at the periphery of the active portion or lattice, and in fact are preferably so positioned in order that they be nqt subjected to the 85 extremely high neutron densities existing near the center of the reactor. 

It is an object of the present invention, then to provide a chain reacting system having a neutron moderator characterized by very high slowing capability while at the same time having very low neutron absorption so that neutron losses in the slowing medium are reduced to a minimum. 

FIGS. 2 to 5, inclusive, are diagrams representing four methods of cooling a nuclear fission chain reacting system in accordance with our invention ... 

FIG. 7 is a vertical sectional view of one embodiment of our invention showing the principal features of our nuclear chain reacting system ... 

FIG. 15 is an enlarged vertical sectional view of a portion of the apparatus shown in FIG. 13 showing one type of circulating, pumping and valving system particularly adapted for use with our chain reacting system ... 

FIG. 18 is a diagram representing distribution of neu- neutron capture cross-section. Bismuth, deuterium and tron losses in our self-sustaining chain reacting system. helium are good moderating elements. The ability to... 

A nuclear fission chain reacting system comprising... 

In a continuously operating nuclear fission chain reacting system comprising a slurry of uranium and... 

In a nuclear fission chain reacting system a reaction tank having a semispherical portion surmounted by a... 

Record of neutron intensity obtained with the first chain-reacting system on 2 December 1942 (Glasstone 1967)... 

Neutron spectra of some chain-reacting systems (Choppin and Rydberg 1980). The vertical axis shows the Tlux energy/ i.e., the product of neutron flux and neutron energy ... 

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