Gamma ray spectrometric analysis

Thermal neutrons are readily captured through the I(n, ) reaction to produce the radioactive nuclide ( 1/2 25min), which emits a characteristic gamma energy of 443 keV in conjunction with beta decay. In order to determine quantitatively the iodine content in the sample, a known quantity of iodine standard is irradiated in parallel with the sample for direct comparison in gamma ray spectrometric analysis. 

The typical purification method for rare earths is coprecipitation with ferric hydroxide, dissolution in dilute acid, precipitation as fluoride in strong mineral acid solution, dissolution in strong nitric acid with boric acid to complex fluoride, and precipitation for counting as the oxalate in dilute acid solution (Stevenson and Nervik 1961). Because Pm has no stable isotope, another rare earth (such as lanthanum) is added as carrier. The " Pm precipitate can be counted with a proportional counter, or can be dissolved and measured with an LS counter because of the low beta-particle energy. If small amounts of the other rare earth radionuclides are detected by gamma-ray spectrometric analysis, the beta-particle count rate of Pm can be calculated by difference. 

Neutron activated gamma-ray spectrometric analysis. t Atomic absorption spectrophotometry. 

Neutron activated gamma-ray spectrometric analysis (Na, Cl, Al, Mn, Ca, and P), atomic absorption spectrophotometry (K, Mg, Zn, Cu, and Fe), or a fluoride-specific electrode (F). a Atomic absorption spectrophotometry (Ca), and colorimetric method (P). 

Bulk enamel from premolars of 14-16 yrs male and female patients, selected population of Stockholm Sweden, determined by neutron activated gamma-ray spectrometric analysis. Standard deviation, . 

Soremark, R. and Samsahl, K. (1961) Gamma-ray spectrometric analysis of elements in normal human enamel. Arch. Oral Bio., Special Suppl, 6,275-283. 

Air-dried soil was passed repeatedly through a 2-mm sieve and quartered to produce material with a grain size less than 0.5 mm. The sieved fraction was then dried at 105°C to a constant weight and stored in counting vessels of volume 125 cm and known geometry for gamma-spectrometric analysis. Prior to X-ray fluorescence (XRF) analyses, sieved and dried soil samples were pressed into pellets. 

Determination of uranium in soil samples can be carried out by nondestructive analysis (NDA) methods that do not require separation of uranium (needed for alpha spectrometry or TIMS) or even digestion of the soil for analysis by ICPMS, ICPAES, or some other spectroscopic methods. These NDA methods can be divided into passive techniques that utilize the natural radioactive mission (gamma and x-ray) of the uranium and progeny radionuclides or active methods where neutrons or electromagnetic radiation are used to excite the uranium and the resultant emissions (gamma, x-rays, or neutrons) are monitored. In many cases, sample preparation is simpler for these nondestructive methods but the requiranent of a neutron source (from a nuclear reactor in many cases) or a radioactive source (x-ray or gamma) and relatively complex calibration and data interpretation procedures make the use of these techniques competitive only in some applications. In addition, the detection limits are usually inferior to the mass spectrometric techniques and the isotopic composition is not readily obtainable. 

There are several potential sources of radioactive materials that can contaminate water (see Chapter 4, Section 4.14). Radioactive contamination of water is normally detected by measurements of gross P activity and gross a activity, a procedure that is simpler than detecting individual isotopes. The measurement is made from a sample formed by evaporating water to a very thin layer on a small pan, which is then inserted inside an internal proportional counter. This setup is necessary because P particles can penetrate only very thin detector windows, and a particles have essentially no penetrating power. More detailed information can be obtained for radionuclides that anit y-rays by the use of gamma spectrum analysis. This technique employs solid-state detectors to resolve rather closely spaced y peaks characteristic of specific isotopes in the sample s spectra. In conjunction with multichannel spectrometric data analysis, it is possible to determine a number of radionuclides in the same sample without chemical separation. This method requires minimal sample preparation. 

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