Experimental Reactor Physics

The neutron moderati properties ot polyetl lene (CHa) have been staled experimentally and ana ically at General Atomic ai. bther laboratories. Measurements have been, made of the neutron spectra with various 1/v absorber concentrations and temperatures as an over-till check idf the scattering model for the polyethylene molecule. Since the scattering model-for polyethylene should be very similar to that for paraffin, a homogeneous mixture of (UF 4-paraffin) was obtained from ORNL for quasi-Infinite-medium lieutron-spectrum measurements. This material has been studied extensively in critical experiments. 

The background of delayed neutrons emanating from the assembly had to be subtracted from the measured flux. To determine the magnitude of this delayed-neutron background(Nd)ithe complete time behavior of the neutron density was measured at the base of the re-entrant tube with a small fission counter, and the ratio (A) of the total. number of delayed neutrons to the total number of prompt neutrons was determined, tt can be shown that the appropriate delayed-neutrcm background to subtract is given 

GOLDMAN, D. T., and F. D. FEDERIOll, The Calculation of Neutron Spectra for Perfect Gas, Water and Polyethylene-Moderated Systems, KAPL-2000-16, (Jan, 1962). 

SUMMIT an IBM 7090 program for the computation of crystalline Scattering Kernels, General Atomic Report GA-2492, (Feb. 1962). 

BEYSTER, J. R., et aL, Integral Neutron Thermali-zation, Quarterly Progress Report for the period ending Dec. 31, 1963, General Atomic Report GA-4881 (in press). 

---

A Basic Experimental Reactor Physics Program on UOj-PuOi-HjO Lattices, J. De-... 

Later in the project after the main parameters had been fixed it was necessary to build up a detailed picture of the expected performance tracing the interactions between the nuclear and thermal hydraulic aspects. This led to the development of the PATRIARCH scheme (see Pig. 1) of computer codes which forms a set of modular compatible programmes designed to cover all performance aspects. It was of course necessary to relate the development of PATRIARCH very closely to the flow of data arising from the experimental reactor physics programme and from the thermal and hydraulic rigs (ref. 4). 

Additionally, two other reactors, the international thermonuclear experimental reactor (ITER) for which the location is under negotiation, and the Tokamak Physics Experiment at PPPL, Princeton, New Jersey, are proposed. The most impressive advances have been obtained on the three biggest tokamaks, TETR, JET, andJT-60, which are located in the United States, Europe, and Japan, respectively. As of this writing fusion energy development in the United States is dependent on federal binding (10—12). 

On November 16, 1942, Los Alamos, New Mexico, was selected as the central site (Site Y) for a laboratory to research the physics and design of atomic weapons. Site X was at Oak Ridge, Tennessee and consisted of an experimental reactor, chemical separation plant, and electromagnetic separation facility. An area near... 

To adequately treat these many applications and to illustrate the specific ways in which decay data make useful, if not crucial, contributions to them is a task that lies beyond the space and time limitations of this paper. We have thus chosen to limit the scope of this presentation to the discussion of several selected examples, drawn mostly from the area of fission-reactor physics. These include the results of recent significant developments in actinide-nuclide decay data and, in the spirit of this symposium, decay data of fission-product nuclides off the line of p stability and some of the problems and challenges they present to both experimental capabilities and nuclear theory. 

Bezhunov, G.M., et al. (1989) Experimental and analytical study of prompt neutron lifetime in fast reactors with moderation zones in the reflector, in Neutronic problems of nuclear power system safety paper theses VI AU-Union Workshop on Reactor Physics, Tsniiatominform Publishers, Moscow, pp.48-50 (in Russian). 

R. W. Conn, V. A. Chuyanov, N. Inoue, D. R. Sweetman, The International Thermonuclear Experimental Reactor, ientific American, April 1992, 75 J. G. Cordey, R. J. Goldston, R. R. Parker, Progress Toward a Tokomak Fusion Reactor, Physics Today, Jan. 1992, 22... 

In the nuclear research centers, the wastes are obtained from research and experimental reactors, hot cells, pilot plants, and decontamination services. These wastes have varying physical, chemical, and radioactive nature due to the great diversity of isotopes used and the wide range of processes in which they are applied. 

The selection and design of a reactor for bench-scale kinetic experiments should be considered case by case. It is important to stress, however, that one should not try to build a bench-scale replica of what is believed to be or is the industrial reactor. Industrial reactors are designed to operate a process in a profitable way, which is not the case for experimental reactors. In industrial reactors heat, mass and momentum transport has to occur in an economically justifiable way, leading in general to temperature, concentration and/or pressure gradients inside the reactor. Also, the hydrodynamics can be rather complicated. Fluidized beds, bubble columns and trickle-flow reactors require model equations that involve several physical parameters, besides the intrinsic kinetic parameters. Empirical... 

The above list essentially summarizes the tasks performed by a reaction engineer in the development of a new reaction process. The quality of the final result of this reaction engineering methodology, whether automated or not, is intrinsically linked to a necessary hardware component of this process the experimental reactor system. Any shortcomings of this physical system would be manifest as errors or uncertainties in the final reactor design. 

Even if the full details of the dynamics of moderator atom motion were known, it would not be possible to incorporate all this information into neutron thermalization calculations for reactors. Therefore, it is necessary to work with somewhat simplified models. Especially in the absence of a complete knowledge of the appropriate differential cross sections, it is necessary to compare calculations using these models with clean experimental information on the neutron distribution in position and energy for configurations of interest in reactor physics. 

An additional equation can be derived from (9) and (10) which is very important in experimental low power reactor physics. When a reactor undergoes a step-insertion of reactivity, which renders the reactor slightly supercritical, for example, and when transient disturbances die out, the neutron and delayed emitter populations will behave as e, where o) is the largest root of the inhour equation, obtained from (9) and (10) by taking fi(t) F(t) e ... 

A. E. DUNKLEE, The Heavy Water System of the Process Development Pile, DP-567, E. I. du Pont de Nemours and Co., Savannah River laboratory (1961) J. L. CRANDALL, Status of the United States Effort in DiO Reactor Physics, DP-787, E. I. du Pont de Nemours and Co.. Savannah River Laboratory (1962) J. L. CRANDALL. Efficacy of Experimental Physics Studies on Heavy Water Lattices." DP-833. E. I. du Pont de Nemours and Co., Savannah River Laboratory (1963). 

From the time that a neutron chain reaction was first envisioned to its experimental verification with the CP-1 critical pile in 1942 to the advanced reactor designs of today, the principal measure of the propensity for a system to sustain a neutron chain reaction has been the /c-effective eigenvalue. In this section, we review the mathematical and physical background of criticality that both reactor physics and criticality safety have in common. This will involve several steps ... 

Until 1991, RP-0 was used for personnel training in the fields of reactor operation, reactor maintenance and reactor physics (calculus and experimental). Currently it is used as a mock-up of the RP-10 research reactor, for experiments to measure nuclear parameters, and for teaching and training. The reactor has a nominal power of 10 W and it is operated three days... 

The quality of the containment structure or other means of confinement The utilization of the reactor (experimental devices, tests and reactor physics experiments) ... 

Carpenter, S.G. et al., Experimental Studies of 6000 litre LMFBR Cores at ZPPR. Proc. Conf. Advances in Reactor Physics and Shielding (p. 521) Sim Valley (1980). 

---