Nuclear measurements, detection

In the discussion that follows we refer to nuclear activation detection reactions in lieu of analysis reactions since the signals that are measured are not necessarily always from a radioactive product. Again, we will use standard nuclear physics notation in specifying nuclear reactions, namely ... 

P. J. Ouseph, Introduction to Nuclear Radiation Detection, Plenum Press. New York, 1975 W. B. Mann, R. L. Ayres, S. B. Garlinkel, Radioactivity and its Measurement, 2nd ed.. Pergamon, Oxford, 1980... 

The combination of collinear fast-beam laser spectroscopy and P-RADOP (radiation-detected optical pumping) has been used to measure nuclear spins and moments of neutron-rich isotopes of the light alkali elements jLi [72-74] and Na [75]. Here, the optically pumped fast atomic beam is implanted into a single crystal placed in a static magnetic field. The NMR signal is destroying the nuclear polarization detected by measuring the p-decay asymmetry. 

Another widely used method is solid state nuclear track detection. In the case of radon, an alpha track detector is used. It consists of a small piece of plastic enclosed in a container with a filter-covered opening. Alpha particles in the air strike the plastic and produce submicroscopic damage tracks. At the end of the measurement period the plastic is placed in a caustic solution that accentuates the damage tracks. The tracks are then counted using a microscope or automated counting system. 

The most widely used NDA instruments rely on the detection of nuclear radiation such as gamma rays and/or neutrons. Physical measurement techniques are also used with available instruments that measure heat, weight, liquid volume, thickness, and light emission/absorption. These physical techniques may be applied by themselves, or they may be used in combination with other nuclear measurements to provide quantitative measurements of the nuclear material. The general reference on the theory and application of passive NDA (PANDA) is given by reference (Reilly et al. 1991) and its addendum (Reilly et al. 2007). 

Three control methods are used on each bead-end system. First, the poison is mixed according to standard operating procedures and the measurements are affirmed by the operator s supervisor. Second, the poisoned solution is stirred, sampled, analyzed, and the analysis reported while still in the mix tank, Finally, a Nuclear Poison Detection System (NPDS) must show an acceptable poison concentration before the solution can be transferred. The NPDS provides a continuous monitoring of the boron concentration in the solution and automatic alarm and shutoff of the acid feed valves should the... 

Darke, A., Finer, E.G., Moorhouse, R., Rees, D.A. (1975) Studies of hyalmonate solutions by nuclear magnetic relaxation measurements. Detection of covalently-defined, stiff segments within the flexible chains. Journal of Molecular Biolology, 99 (3), 477-486. 

With the use of Cs source tomographic layer-by-layer study of nuclear fuel within a range of 5 to 12 g/sm is conducted. In the specialized tomograph the initial information measurement time is 5-30 min, the tomograms restoration time is 4-10 min. The sensitivity to a various density is about 5% when detecting local areas with a diameter exceeding 0.5mm. 

Therefore, in NMR, one observes collective nuclear spin motions at the Lannor frequency. Thus the frequency of NMR detection is proportional to Nuclear magnetic moments are connnonly measured either... 

In 1964, workers at the Joint Nuclear Research Institute at Dubna (U.S.S.R.) bombarded plutonium with accelerated 113 to 115 MeV neon ions. By measuring fission tracks in a special glass with a microscope, they detected an isotope that decays by spontaneous fission. They suggested that this isotope, which had a half-life of 0.3 +/- 0.1 s might be 260-104, produced by the following reaction 242Pu + 22Ne —> 104 +4n. 

During World War II and thereafter, the methods of x-ray detection were improved until it is now a matter of simple routine to measure relative x-ray intensity easily and precisely. This improvement, which was accelerated by the rapid progress in nuclear physics, has promoted a rapidly growing appreciation of the great advantages that can attend the application of x-ray absorption and emission to chemical analysis. In their rush to make these applications, analytical chemists have occasionally made discoveries predictable from earlier work, usually by physicists, in the field of x-rays. 

The NAA measurements on the paper samples were made at the Breazeale Nuclear Reactor Facility at the Pennsylvania State University with a TRIGA Mark III reactor at a flux of about 1013 n/cm2-sec. Samples were irradiated from 2 to 20 min and counted for 2000 sec, after a 90 min decay time for Ba and a 60 hr decay for Sb, Analyses were performed instrumentally, without radiochemical separation, using a 35cm3 coaxial Ge-Li detector and a 4096-channel pulse height analyzer. With these procedures, detection limits for Ba and Sb were 0.02ug and 0.001 ug, respectively. These sensitivities are comparable to those obtained by GA s radiochemical separation procedure, and are made possible by the use of the higher neutron output from the more powerful reactor and in combination with the higher resolution solid state detector... 

The use of nuclear techniques for the detection of buried expls (in mines) has been investigated by the US Army over the past 25 years. The basic approach is the use of a direct beam of highly penetrating radiation to irradiate the soil and the measurement of a reflected, scattered, induced or secondary signal to indicate the presence of a buried mine. A complete historical review and analysis of this work has been prepared by Coleman et al (Ref 18), A brief summary of the highlights of the overall effort is provided here... 

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