The in vivo neutron activation analysis of calcium in the skeleton of normal subjects,with hypokinesia and bone diseases

A facility developed for the in-vivo neutron activation analysis (IVNAA) of calcium in some parts of tubular limb bones, in the hand, foot and spine is described. The⁴⁸Ca(n, )⁴⁹Ca reaction is used, the gamma-rays of⁴⁹Ca (E=3.08 MeV, T_1/2=8.8 min) are measured. The irradiation is carried out with five of ten²³⁸Pu–Be neutron sources with a source stength of 5·10⁷ n s^–1 each arranged in a bath filled with water. NaI(T1) detectors (from 2 to 4 in number) of 150×100 mm size supplied with lead and shadow shielding are used in the counting unit. The construction of the facility started in 1972 and has been in operation since 1974. It has been used for the examination of patients suffering from limb bone tumors, of children with rickets-like and similar diseases and for studies in space medicine.     

An241Am−Be source based thermal neutron activation analysis facility at KFUPM

An instrumental thermal neutron activation analysis facility based, on a 16 Ci²⁴¹ Am–Be source, a high resolution -ray spectrometry setup and a PC-based data acquisition system at KFUPM is described. The thermal neutron flux distribution was determined from the induced activities of high purity indium foils. The absolute thermal neutron flux was calculated from the activities of bare and cadmium-covered gold foils at a position of 3 cm from the soource at which the flux reaches a maximum. The facility tests were carried out with the determination of manganese concentrations in six types of industrially important steel samples. The result of 1.33% manganese in SS-304 steel sample was in excellent agreement with the literature value. The method is nondestructive, economical and ideal for bulk analysis.     

Preliminary phantom measurements for in vivo activation analysis of calcium in the human forearm

Preliminary phantom measurements were carried out for regional determination of calcium in the human forearm. Two paraffine phantoms /large and small/ were activated, either in the free space or surrounded by paraffine plates, by a²⁵²Cf neutron source. Differences between neutron flux densities in positions of the ulna and radius are discussed.     

Low-Flux NAA Applications at the Savannah River Site

Neutron activation analysis using low-flux isotopic neutron sources is put to use in addressing areas of applied interest in managing the Savannah River Site. Some of the applications are unique due the site's operating history and its chemical processing facilities. Because sensitivity needs for many of the applications are not severe, they can be accomplished using a 6 mg ²⁵²Cf neutron activation analysis facility. Overviews of the facility and several example applications are presented.     

Measurements of fluoride in bone biopsies by neutron activation analysis for the clinical study of osteoporosis

A procedure has been developed to measure fluoride concentration in bone biopsies by neutron activation analysis /NAA/. The NAA procedure is non-destructive so that the bone biopsies can be used subsequently for histological evaluation. The fluoride content is expressed as F/Ca ratio in the bone samples. The fluoride and calcium are measured using the reactions:¹⁹F/n, /²⁰F /t=11.2 s/ and⁴⁸Ca/n,/⁴⁹Ca/t=8.8 m/, respectively. The F/Ca ratio normalizes the fluoride to bone mineral avoiding the use of bone weight which is unreliable with fresh biopsy samples. This ratio also corrects for variations in neutron flux and gamma counting efficiencies. Results by this procedure were compared to biochemical determinations using an ion-selective electrode for fluoride and atomic absorption for calcium. The two methods gave results which agreed within ±5% which is the precision of the NNA procedure. The NAA method provides a simple and non-destructive procedure for fluoride measurement in bone biopsies for clinical studies. The method is now routinely used in our clinical studies for the fluoride measurements on biopsies from osteoporotic patients treated with fluoride therapy for nearly four years.     

Detector shielding in the study of osteoporosis by in vivo neutron activation analysis

Calcium may be measured in vivo by neutron activation analysis /IVNAA/, observing the 3.1 MeV -ray from the decay of⁴⁹Ca. Normally the detection of this -ray is done in a heavily shielded whole body counter. It is shown that the use of shielding is unnecessary. As a result, the cost of building an IVNAA facility for Ca is very much reduced.     

Use of D–T-produced fast neutrons for in vivo body composition analysis: a reference method for nutritional assessment in the elderly

Body composition has become the main outcome of many nutritional intervention studies including osteoporosis, malnutrition, obesity, AIDS, and aging. Traditional indirect body composition methods developed with healthy young adults do not apply to the elderly or diseased. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. Non-bone phosphorus for muscle is measured by the ³¹P(n,)²⁸Al reaction, and nitrogen for protein via the ¹⁴N(n,2n)¹³N fast neutron reaction. Inelastic neutron scattering is used to measure total body carbon and oxygen. Body fat is derived from carbon after correcting for contributions from protein, bone, and glycogen. Carbon-to-oxygen ratio (C/O) is used to measure the distribution of fat and lean tissue in the body and to monitor small changes of lean mass. A sealed, D–T neutron generator is used for the production of fast neutrons. Carbon and oxygen mass and their ratio are measured in vivo at a radiation exposure of less than 0.06 mSv. Gamma-ray spectra are collected using large BGO detectors and analyzed for the 4.43 MeV state of carbon and 6.13 MeV state of oxygen, simultaneously with the irradiation. P and N analysis by delayed fast neutron activation is performed by transferring the patient to a shielded room equipped with an array of NaI(Tl) detectors. A combination of measurements makes possible the assessment of the quality of fat-free mass. The neutron generator system is used to evaluate the efficacy of new treatments, to study mechanisms of lean tissue depletion with aging, and to investigate methods for preserving function and quality of life in the elderly. It is also used as a reference method for the validation of portable instruments of nutritional assessment.     

Uses of PGAA at the Dalat reactor

A facility for neutron capture prompt -ray spectroscopy for activation analysis has been intstalled at the tangential beam tube of the 500 kW Dalat reactor. Using a single crystal of silicon for filtering the thermal neutron beam and the 73 cm³ HP-G detector shielded by common materials with flexible configurations suitable to various samples, LOD of nearly 30 elements were estimated. Applications of PGAA in the determination of elemental concentrations in biological, environmental, geological and industrial product samples are presented.     

Total body calcium by neutron activation analysis: Reference data for children

There is a paucity of data on the chemical composition of the humanbody during growth. Total body calcium (TBCa) has been reported for only onemale child, aged 41/2 yr. We have obtained TBCa values for 25 children and27 young women using in vivo neutron activation analysis. Our TBCa resultswere lower than those reported for the one male cadaver, as well as the estimatesderived for the Reference Man model. We conclude that the referencevalues for TBCa may need to be adjusted to appropriately describe skeletalmineralization of contemporary children.     

Large-sample neutron activation analysis: Present status and prospects

Neutron activation analysis is attractive for trace-element determinations in large samples. Facilities for reactor irradiation and -ray spectrometry of kilogram-size cylindrical samples are described. The thermal neutron flux is ca. 5·10¹²m^–2·s^–1 with a _th/ _epi>10⁴, so neutron self-thermalization can be neglected. The correction for the neutron attenuation within the sample is derived from measurement of the neutron flux depression just outside the sample. Correction for -attenuation in the sample is performed via linear attenuation coefficients derived via transmission measurements. Also the natural radioactivity in the sample is taken into account. Examples are given of materials to which large sample INAA has been applied successfully, and further lines of development and exploration are indicated.     

Instrumental neutron activation analysis of Al,V and Ti employing252Cf as a thermal neutron source

A rapid method for the determination of Al, V and Ti has been developed and is used for the analysis of these elements in different ores and alloys. An isotopic neutron source²⁵²Cf having a thermal neutron flux of the order of 8.5×10⁷ n·cm^–2 sec^–1 has been used for thermal neutron bombardment. Activity measurements were performed on a HPGe detector coupled to a PC based MCA unit. Depending on the half-life of the (n, ) product, different irradiation and cooling times were employed and thus the elements of interest were analyzed sequentially.     

On-stream measurement of heavy water concentration by intermediate neutron moderation

A method of measuring heavy water concentration is described based on intermediate neutron moderation. With a 1.6 g²⁵²Cf neutron source and a BF₃ proportional counter, for 500 ml samples, accuracies of the measurements are within ±0.02 mol% in the concentration range of 0100 mol% with 210 minute counting. To evaluate the practical effectiveness of the method, a model apparatus was built for routine use in laboratory and on-stream measurements. It was successfully applied to observe the substitution process between light water and heavy water in an ion exchange resin tower at a nuclear power station.     

Measurement of thermal neutron capture cross sections of 237Np and 242Pu using prompt gamma neutron activation

Several samples of ²³⁷Np and ²⁴²Pu were irradiated in the guided cold neutron beam of the prompt gamma activation analysis facility at the Budapest Research Reactor. The thermal neutron capture cross sections of ²³⁷ Np and ²⁴²Pu were evaluated from the obtained prompt and delayed gamma ray data. The thermal neutron capture cross sections for ²³⁷Np(n,γ)²³⁸Np was found to be $ \sigma_{0} ({}^{237}{\text{Np}}) = 170.4 \pm 7.4\,{\text{b}} $ and for ²⁴²Pu(n,γ)²⁴³Pu to be $ \sigma_{0} ({}^{242}{\text{Pu}}) = 19.6 \pm 3.9\,{\text{b}} $ .     

Determination of phosphorus in biological samples by thermal neutron activation followed by β--counting

Phosphorus has been determined using the ^- emitter³²P by instrumental neutron activation analysis (INAA) in several NBS and IAEA standards and samples of biological origin such as human and animal blood, cancerous tissue, edible plant leaves, diets, milk samples, etc. The method involves thermal neutron irradiation for 2–10 h in a reactor followed by ^--counting on an end-window gas flow proportional counter using an aluminium filter. The results are within ±10% of the certified values in most cases.     

Characterization of the neutron flux gradients in typical irradiation channels of a TRIGA Mark II reactor

The neutron distribution in a defined volume (gradient) for different matrices (air, water, cellulose, biological material and silicon dioxide) in two typical irradiation channels (pneumatic tube (PT) and IC40-channel in the carousel facility) in the TRIGA Mark II reactor at the Joef Stefan Institute (IJS) was studied. Our experiment was based on inserting Fe wires (flux monitors) into the chosen matrices. The wires were cut into small pieces after irradiation and the induced activities of ⁵⁹Fe measured. The results showed that for the studied geometry the average spatial thermal neutron flux inhomogeneities (for five studied matrices) are about 2.3% in the PT-channel and about 2.9% in the IC40-channel.     

Prompt and delayed radiation measurements in the elemental analysis of biological materials: The case for neutron induced gamma-ray emission tomography

Nuclear and atomic methods of analysis, which rely on the detection of prompt and delayed radiations, emitted as a result of interactions between radiation probe and target, for determining the elemental concentration in vivo and in vitro, are summarily reviewed, with reference to bone analysis; the demand for methods which provide information about elemental distribution is highlighted. The way neutrons can be used as probes to investigate the composition and structure of objects by employed the principles of computerised tomography are outlined and the novel modes of utilisation are briefly described: neutron transmission tomography, neutron induced prompt gammaray emission tomography and neutron induced delayed gamma-ray emission tomography. The latter method, alternatively termed neutron activation tomography, is then used to determine on-destructively the distribution of Na in selected planes of a human tibia, in vitro, by measuring the activity of²⁴Na using a NaI(Tl) and a Ge(Li) detector in a tomographic scanner which incorporates a microcomputer for control, data acquisition and image reconstruction. The problems of attenuation and scattering are discussed as are the limitations for quantitative results of this useful new mode of tomography which provided information about composition and elemental distribution in a material.     

A new application of neutron activation analysis with239U to determine uranium in groundwaters

A rapid neutron activation method was developed to determine very low levels of uranium (gl^–1) in groundwater from the Palmyrides region, Central Syria. The²³⁹U -ray at 74.7 keV energy was used in the measurements. Results of this technique were compared against the conventional neutron activation analysis (INAA) with²³⁹Np and the laser-induced fluoremetry (LIF). In general, the three data sets showed a very good agreement. The described method provides good accuracy, precision and low detection limit, particularly when the total dissolved solids (TDS) of the samples is low.     

Application of an image scanner for determination of boron in glass by a nuclear track technique

For boron concentration in the range of 010%, a 600 g²⁵²Cf neutron source was used for thermal neutron irradiation. As for the track counting technique, a visual observation method by human eye and an automatic counting method with an image scanner showed a good agreement between the determinations by both methods. The latter is useful for improving accuracy in elemental determination by using the nuclear track technique because it gives reproducible count values which are free from human error in comparison with the former.     

High precision elemental abundances for tektites and crater glasses-thorium,uranium and potassium

Thorium, uranium and potassium mean abundances for 15 Ivory Coast tektites, 23 Australites, 10 Philippinites, 25 Thailandites, 16 Bediasites and 12 Moldavites are reported. Abundances are also reported for Muong Nong type tektites, Nordlinger Ries crater glass, Bosumtwi crater glass and Darwin crater glass. Previous measurements are reviewed. The value of the present work lies in the fact that high precision instrumental neutron activation analysis was employed to measure a large number of tektites encompassing the major strewn fields. Four independent measurements of thorium were made for each specimen with two Ge(Li) gamma spectrometers. Two of the measurements were based on the 312 keV gamma of²³³Pa, while the other two measurements were based on the uranium and X-rays which accompany the decay of²³³Pa. Internal consistency among the four thorium measurements is high. The uranium measurements were based on the 106 keV gamma of²³⁹Np, while potassium was measured from the 1524 keV gamma of⁴²K.     

A new gamma-ray spectrum catalog and library for PGAA

New measurements have been performed at the PGAA facility at the Budapest Research Reactor (BRR) in order to create a prompt -ray catalog for qualitative and quantitative analysis. The measured spectra were accurately analyzed by HYPERMET-PC. Prompt -ray energies and associated -ray production cross-sections have been determined by internal standardization. The resulting catalog contains prompt -ray data from neutron capture and other reactions such as (n,), and decay -ray data from short-lived reaction products. Data have been measured for nearly all stable elements, from hydrogen to uranium. Generally, data for several isotopes are given, to enable isotopic analysis as well. The whole library, including elemental spectra, will be available as a book.