Reactor physics experiment

R. Chawla, An Assessment of Methods and Data for Predicting Integral Properties for Thermal Reactor Physics Experiments, AEEW-R797 (1972). 

Beall, S. E., Reactor Physics Experiments in the MTR Mock-Up, ORNL-972... 

In the core design of large FBRs, it is essential to improve the prediction accuracy of nuclear characteristics from the viewpoint of both reducing construction cost and insuring plant reliability. Extensive work is being performed in this context to accumulate and evaluate many results of reactor physics experiments in FBR field. As a part of the effort to develop a standard data base for large FBR core nuclear design, the physical consistency of JUPITER experiment and analysis was evaluated by full use of sensitivity analysis, effect of different nuclear data Ubraries and q>pUcation of most-detailed analytical tools. 

These experiments are similar to the reactor physics experiments discussed earlier. However, the emphasis is now on operations and reactor control and instrumentation systems and understanding basic physics measurements. The objective is to provide the student with operations experience similar to that of a reactor operator. 

All experiments require a reactor operator. Some reactor physics experiments (e.g., a critical experiment) will require measurements and data collection in addition to that provided by the existing reactor instrumentation. In this case, a staff member is required to set up and operate the equipment. The reactor operator or another individual must be capable of assuring understanding of the experiment and its results for the students involved. 

Reactor physics experiments that require instrumentation not available in the reactor instrumentation will need some funding for this instrumentation. The cost will depend on level of sophistication desired in the experiment and may vary from US 5000 to US 40 000. 

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

A special programme of reactor physics experiments is in progress with the objective of improving the accuracy of nuclear calculations for natural uranium SGHWRs by providing calibration data. 

The process control subsystem was developed to allow control of the moderator level and temperature, in order to perform reactor physics experiments. It was made up of "conventional" instruments, which means AP transmitters (to measure level), thermocouple sensors (to measure temperature), and a single loop controller. 

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). 

Several of the reactor physics parameters are both measurable and calculable from more fundamental properties such as the energy-dependent neutron cross sections and atom number densities. An extensive database. Evaluated Nuclear Data Files (ENDF), has been maintained over several decades. There is an interplay between theory and experiment to guide design of a reactor, as in other engineering systems. 

The value oik a can, in certain circumstances, be determined by purely physical experiments in the reactor. For instance, kifi may be evaluated from the observed total rate of absorption in the case of a piston-like countercurrent flow of the two phases, where C% becomes a known function of CaOj or where the gas and the liquid are well stirred, so that and Cao are the same at all points. 

Liquid-hydrogen/solid-air explosions have been carried out in a closed volume to assess the possible hazards of an explosion in an in-pile nuclear experiment. At A.E.R.E. Harwell there are a number of current and prospective nuclear-physics experiments that use chambers adjacent to the reactor core, filled with liquid hydrogen in order to moderate the reactor neutron flux and produce collimated beams of low-energy neutrons. These moderator chambers are generally surrounded by a vacuum tube of up to 7 ft in length and 4 to 12 in. in diameter. 

Session 3 Fast reactor physics and engineering experiments and analyses... 

FAST REACTOR PHYSICS AND ENGINEERING EXPERIMENTS AND ANALYSES... 

The start-up and operation of the Na-cooled fast reactors Phenix and Superphenix has provided a large amount of valuable experience, as the decommissioning of Superphenix is doing right now. We shall focus here on the feedback of the neutron physics experiments performed in both reactors on the neutron physics calculation tools and methods. 

The power map distribution is deduced from the measurement of the sodium temperature at the output of each reactor sub assembly. This is not a purely neutron physics experiment and assumptions on the way the sodium flows in the sub assembly are of major importance in this measurement. However after checking the various sources of uncertainties, only a correction for the mixing of sodium from different sub assemblies before detection by the thermocouple has been found to be significant. 

The value of kga can in certain circumstances be determined by purely physical experiments in the reactor, for instance in the case of piston-like countercurrent gas-liquid flow or when both phases are wel1-stirred. However, the rate of absorption depends on the residence time distribution in both phases that may be undetermined and in addition there is normally an appreciable resistance on the liquid side that must be taken into account. Thus the liquid side resistance can be eliminated and the rate of absorption can be made independent of the liquid side residence time distribution by using a solution which reacts instantaneously and irreversibly with the dissolved gas so that there is no back-pressure. Therefore,... 

A neutron zero power facility with only SOkg U-235 has been built up in 1970, then moved to the South-West center of Reactor Engineering in Sichuan P rovince. Basic zero power physics experiments have been done at diis facility including critical parameter measurements, fission rates, neutron flux distribution, neutron spectrum, material reactivity etc. in 1988, it was removed to ClAE again, and now it has been rebuilt and will be used for proving of the neutronics experiment medtods which will be served to CEFR first start-up and to primary test for die neutronic and other radiation detectors. It is considered also it will be valuable to the evaluation of some specimen nuclear cross section using its hard spectrum. 

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