Neutron Generator Facility

Battelle has developed instrumental neutron activation analysis (INAA) techniques which permit very sensitive and accurate multielement analysis of approximately 40 elements in coal and fly ash. These techniques, which will be described in this work, form the basis for extensive environmental studies of the effluent from coal-powered generating facilities and other pollution sources. 

The current availability of small portable 14 MeV neutron generators and the future availability of high intensity 252Cf spontaneous fission neutron sources will certainly result in the wide spread use of activation techniques for non-destructive "on-stream" product analysis in industry. The cost of the required instrumentation for many types of activation analysis is not excessive, as compared to the cost of other modem analytical instrumentation. The simple off-on operation of the new sealed-tube neutron generators and minimal maintenance associated with the use of an isotopic Z5ZCf neutron source will permit operation of the analytical facility with technician-level personnel. The versatility of the activation technique justifies its inclusion among the other major analytical techniques employed in any modem analytical facility. 

In order to control subcriticality of SRP s storage facilities by the stationary method, it is necessary to know the induced fission neutron generation rate per gram of fuel (Qind) and the rate of neutron generation by above-mentioned sources per gram of fuel (Qsp) in the maximum neutron flux points [17], If Qsp and Qmd are known, the system multiplication can be written in the following way ... 

Pulsed reactivity measurements were made, in the Subcritical Eiqperiment Facility at the vannah River Laboratory. A rigid aluminum support frame maintained accurate spacing within the arrays. The lattices were tolly flooded to achieve an effective infinite H2O reflection. A KAMAN modei A-800 puised-neutron generator was located at the mhtotone 15 cm from toe core. Neutron detectors were placed in the low importance region on toe radial centerline of representative fuel assemblies. The measured fundamental-mode prompt-neutron decay constant, (meas), was determined by standard pulsedineutron techniques (Table I). 

The radiological characteristics of the CSD-C are checked at the facility exit by identical measurement to that performed at the entrance of the ACC facility with two nondestructives measurements stations. The radiological characteristics of the CSD-C are determined by extensive assessment a gamma spectrometry imit with five germanium diode detectors and an active and passive neutron measurement station with 249 neutron counters and two new-generation neutron generators. 

The concrete block walls of the cell housing the generator tube and associated components are 1.7 meters thick. The facility also includes a Kaman Nuclear dual-axis rotator assembly for simultaneous transfer and irradiation of reference and unknown sample, and a dual Na iodide (Nal) scintillation detector system designed for simultaneous counting of activated samples. Automatic transfer of samples between load station to the rotator assembly in front of the target, and back to the count station, is accomplished pneumatically by means of two 1.2cm (i.d.) polyethylene tubes which loop down at both ends of the system and pass underneath the concrete shielding thru a pipe duct. Total one-way traverse distance for the samples is approx 9 meters. In performing quantitative analysis for a particular element by neutron activation, the usual approach is to compare the count rates of an unknown sample with that of a reference standard of known compn irradiated under identical conditions... 

A number of methods have been used to generate sufficiently strong neutron sources, but all current facilities are either fission reactors or spallation sources, so we will consider only these two methods. 

Reactor sources are much more common than spallation sources there are around 20 reactors that produce core fluxes >10 cm s. To generate the proton beam needed for a spallation source requires considerable infrastructure and by 2004 there were only five spallation sources world-wide ISIS [8], IPNS (Argonne, USA) [12], LANSCE (Los Alamos, USA) [13], KENS (Tsukuba, Japan) [14] and SINQ (Villigen, Switzerland) [11] with two more under construction, SNS (Oak Ridge, USA) [9] and J-PARC (Tokai, Japan) [10]. Reactor sources are also much more developed, the first neutron experiments were carried out in the 1950s and the ILL opened in 1975. In contrast the first spallation user facility, opened only in 1980, with ISIS in 1985. 

Tritium collection. Tritium in air is usually in the form of water vapor and less commonly in the elemental or organic-bound forms. It is generated in nature by cosmic-ray interactions, and at nuclear reactors and tritium-production facilities by ternary fission and neutron activation. Tritium as HT tends to oxidize to water vapor in air. Conversion to and from organic-bound tritium occurs in biota (NCRP 1979). 

Noble gas collection. The radioactive argon, krypton, and xenon radioisotopes are monitored near nuclear power plants and related facilities to determine the magnitude of releases of gases generated by fission or neutron activation. Radon radioisotopes and their particulate progeny are measured in homes and mines to determine whether their airborne concentrations are below radiation protection limits. 

ITER is the result of a 1987 agreement, a joint research enterprise for the design of an experimental fusion reactor, supported by the EU, the USA, Japan and by the Community of Independent States. Before getting to this stage, it is firstly necessary to develop and test materials which can withstand a very high neutron flux, with the principal aim not to generate an excessive decay power (DeMarco, 2001). In order to cope with these needs, it has now been decided to build a dedicated experimental facility, the International Fusion Materials Irradiation Facility (IFMIF), based on the Li(d, n) reaction. 

The CAREM reactor under development in Argentina is a 100 MW(th) (about 27 MW(e)) design based on natural circulation. It has an integrated primary circuit comprising the core, steam generators, control rods with their drive mechanisms and the entire primary coolant. Several experiments examining core neutronics and thermal hydraulics have been conducted in test facilities. The construction of a prototype is planned. 

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