Expanding the NAA Analytical Capabilities of Small Research Reactors: Epithermal and Fast NAA with a SLOWPOKE Reactor.
M.J.M. Duke.
SLOWPOKE Reactor Facility, University of Alberta, Edmonton, Alberta, Canada

Abstract
The safety and ease of operation of the SLOWPOKE-2 reactor, together with the stability and reproducibility of its neutron flux, are hallmarks of this much admired research reactor. While the SLOWPOKE has the largest neutron flux to power ratio of any research reactor, historically (and to some degree still to this day) a drawback of the SLOWPOKE reactor, resulting from its inherent safety design, has been the relatively low maximum thermal neutron flux of the reactor (1 x 10¹² n cm^-2 s^-1) when compared to other larger research reactors. This has been somewhat of a disadvantage in the determination of a number of trace elements quantified via their long-lived activation products. Not being able to compete with the high flux research reactors in the determination of some elements that generate long-lived radionuclides has resulted in some limitations when performing NAA with small research reactors. However, this limitation have provided an impetus to those using small research reactors to explore and develop other variations of NAA, including, for example, the use of short-lived radionuclides, cyclical NAA, epithermal NAA and fast NAA, and to develop their own niche. The focus of this presentation will be on the use boron-carbide (B₄C) shields for ENAA and FNAA with a small research reactor.

An additional consequence of the compact design of the SLOWPOKE (and MNSR) reactor assembly, and the proximity of the inner irradiation sites to the reactor core, is the sizeable fast and epithermal neutron components of the inner irradiation sites. While the fast neutron component is generally considered a nuisance because of the fast neutron induced (n,p) and (n,) transmutational interferences to (n,) activation products, both the fast and epithermal neutron components can be used advantageously to expand the NAA analytical capabilities of SLOWPOKE and MNSR reactors. Installation of a permanent Cd-lined inner irradiation site in a SLOWPOKE reactor is not an option as it would destroy the uniformity of the neutron flux in the coaxially arranged inner irradiation sites, another forte of the SLOWPOKE reactor design. Consequently, thermal neutron shields of Cd and/or B₄C that fit into the inner irradiation 7 mL polyethylene irradiation capsules must be employed. The advantages of using B₄C over Cd foil in a low power, small research reactor will be discussed.  

Examples of FNAA and ENAA using B₄C shields and a SLOWPOKE reactor will be presented including the determination of silicon in geological materials (that is competitive with Si determination by XRF), quantification of trace quantities of Br and I in highly saline brines and evaporite minerals, determination of trace U in geological samples, and the analysis of I in foodstuffs. Applications in the analysis of archaeological copper and marble artefacts will also be discussed.

The Transition from Hogdahl-Convention to Westcott- Formalism for the General Applicability of k0-NAA Method.
E.H.K. Akaho^a and B.J.B. Nyarko^b.
^a Department of Nuclear Engineering, National Nuclear Research Institute, Ghana Atomic Energy Commission (GAEC), P.O. Box LG 80, Legon-Accra, Ghana

^b Department of Physics National Nuclear Research Institute, Ghana Atomic Energy Commission (GAEC), P.O. Box LG 80, Legon-Accra, Ghana

Abstract
Expressions were derived and used to establish a transition between Hogdahl- and Westcott-formalisms for k₀-NAA for nuclides following "1/v" and "non-1/v" (n, γ) reactions. The computed effective cross section σ_eff for "non-1/v" nuclides (¹⁷⁶Lu and ¹⁵²Eu) at nine irradiation sites of four different research reactors compared favourably with reported nuclear data in literature. It has been shown mathematically that for the monitor * and any nuclide x, the factor EPI = [σ_eff /σ₀] */ [ σ_eff / σ₀]_x based on flux parameters  of Hogdahl-convention (f and α) is equal to that using the parameters (r′ α)√ (T_n/T₀), g(T_n) and s₀(α) of Westcott-formalism. Using the computed EPI values, the concentrations of nuclides were measured and successfully validated against reported values of Certified Reference Materials (IAEA lichen 336 and IAEA SOIL-7) with 1/v and non-1/v nuclides. This suggests that the present method of analysis could be useful for k₀-NAA to cover both "1/v" and "non-1/v" (n, γ) reaction nuclides. For any irradiation site with the factor ζ = √ [(μ/4).(Tn/T₀)] , it is recommended that the Q₀(α) of the Hogdahl convention be further corrected using the parameter ζ  for the convention to be modified to the form σ_eff = f +Q₀(α) ζ and the parameter used in the evaluation of EPI factor.

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Neutron Activation Analysis in the Peruvian Institute of Nuclear Energy.
P. Bedregal
Chemistry Department – Peruvian Institute of Nuclear Energy
Av. Canada Nº 1470
Lima 41 – Peru

Abstract
This is a presentation of the use of neutron activation analysis technique in the Peruvian Institute of Nuclear Energy (PINE). A description of facilities, analytical procedures and present applications is provided. Finally, future applications of the technique are presented.

Overview of the Work Carried out by the Chemistry Unit of the IAEA Seibersdorf Laboratories.
Kerry I. Burns
Head, Chemistry Unit
Agency's Laboratories Seibersdorf

The mission of the Chemistry Unit is to prepare, characterise, certify and distribute reference materials of terrestrial origin, organise intercomparison exercises and proficiency tests, co-ordinate the activities of the IAEA network of Analytical Laboratories for Monitoring Environmental Radioactivity, provide training and expert assistance to scientists from Member States' (MS) laboratories and provide analytical and radioanalytical support for the benefit of the programmes and projects of the IAEA and its Member States.

The Chemistry Unit's activities are mainly in support of two IAEA sub-programmes; Nutritional and Health-Related Environmental Studies and Radiochemical Applications:

These sub-programmes are designed to:

Assist Member States in the areas of radionuclide measurements and radioactivity monitoring campaigns and collaborate with international organisations in this area,

apply and demonstrate the applicability of nuclear and isotopic techniques in human nutrition research and in studies of non-radioactive environmental pollutants,

assist laboratories in MS in maintaining/improving the quality of their analytical measurements, thus helping them to achieve internationally acceptable levels of quality assurance.

This presentation will provide a brief overview of the work being conducted in the Chemistry Unit and the analytical facilities it has to carry out this work. The final part of the presentation will be concerned with the current status of neutron activation analysis in Seibersdorf and future plans for installation of a fast rabbit facility in the KFKI reactor in Budapest. 
 

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Nuclear Analytical Methods at ICENS Part 3:  Information Management.
J. Preston, C. Grant, G. Lalor and M. Vutchkov
International Centre for Environmental and Nuclear Sciences
University of the West Indies,
Mona, Jamaica

Abstract
The research work of ICENS routinely produce chemical analysis data for many elements, which can have impact for many years to come.  In the current climate of tight research budgetary constraints, it is important for institutes to maximize the returns from these investments in sampling and analysis, both past and present.

To this end ICENS from its inception has sought to ensure that all the results of its analyses would be captured and stored in a computer database.  It has developed a geochemical point sample data store which enables long term data storage and fast retrieval, and is connected to a Geographic Information System so that data can be statistically analysed and any spatial characteristics investigated.

Currently the database holds results for over 90,000 chemical analyses determinations for near 10,000 samples, along with quality control information.

Surviving and a Future for INAA by a Customer Oriented Culture.
P. Bode
Delft University of Technology
Interfaculty Reactor Institute
Mekelweg 15
2629JB Delft
The Netherlands

Abstract
Many NAA groups are nowadays requested to identify beneficiaries for their technique and to start service activities. The principal reasons are budget cuts and/or the fact that (industrial) customers are considered important for public justification of the existence and continuation of the reactor. This implies a change in culture and policy in the technical and organisational management. Several laboratories already identified the problem of acquiring credibility with intended beneficiaries due to lacking objective evidence on quality and reliability of the operations. Method validation, uncertainty evaluation, use of primary standards and certified reference materials, laboratory intercomparison rounds and proficiency testing all serve to control and to demonstrate the quality of the results. Compared to e.g. 30 years ago we now have available more stable equipment, computers and access to more reference materials for method validation and calibration. Numerous papers have been published on sources of error, and on quality control and quality assurance practices. A session on quality control and quality assurance is nowadays included in almost every scientific conference on analytical chemistry. There are numerous publications explaining the advantages and shortcomings of NAA, and many comparisons have been made with other methods for elemental analysis. So, the tools exist, the knowledge is documented and available. But is this all really being used in a proper way?

The typical large spread in the results of proficiency testing schemes indicates that still significant sources of error may either not be accounted for or, even worse, perhaps have not been identified. It can be easily be derived from e.g. the abuse of the terms "quality control" and "quality assurance" in scientific journals that many INAA laboratories –but also the reviewers of manuscripts- do not comprehend this issue. Manuscripts are still being accepted without a proper evaluation of measurement uncertainty and with a misleading standard deviation value after the +/- sign, even though it is already eight years since ISO introduced the Guide on the Expression of Uncertainty in Measurement. Other laboratories consider quality assurance as a bureaucracy, designed for routine activities and a threat for scientific research environments.

Nearly all evaluations on the analytical characteristics of NAA are made 'by radiochemists for radiochemists'. It is much better to put these reviews aside and to learn the customers' view in this. Customers are usually not interested in results of reference material analysis or proficiency testing. A customer wants to get what was asked for, within the given time frame. A customer expects that the analysis can be reproduced and eventually that the INAA laboratory can stand-up in court to defend its results. The absence of evidence on quality assurance in scientific papers indicates that in many cases the INAA laboratory might face serious difficulties in such a case. Moreover, it is also questionable if such results published in literature are really trustworthy and fit for comparisons….

The view of outsiders helps the NAA laboratory to understand the potentials of its technique to provide (scientific) services. This will be presented in terms of a 'SWOT' analysis, an evaluation of  "strengths, weaknesses, opportunities and threats". Examples of successful service contracts will be given.

This contribution further deals with the impact of people on people on the analytical performance and the related dark clouds above INAA will be discussed. Practical examples will be given on the minimum quality control / quality assurance measures in INAA. It will be shown that quality assurance is one of the keys for sustainability, not just for routine services but also for scientific research and development.

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The Brazilian Research Reactor IEA-R1: Its Utilization in Basic and Applied Research and Irradiation Services.
R.N. Saxena
Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP)
São Paulo, Brazil

Abstract
The IEA-R1 research reactor at the Research Reactor Center of the Instituto de Pesquisasa Energéticas e Nucleares (IPEN) is a light water moderated open swimming pool type reactor and uses beryllium and graphite as reflector. The first criticality was achieved on September 16, 1957. Licensed for 5 MW the reactor presently operates at a power of 2 MW thermal on a 64 hours continuous cycle per week. Operational experience and utilization of the reactor was very intense in these almost 45 years and has been extremely important for the development of many research programs in the areas of physics, chemistry, biology and engineering in the institute as well as for the production of radioisotopes for medical and industrial applications and for various irradiation services.

The Research Reactor Center has a three-fold mission of promoting basic and applied research in nuclear and neutron related sciences, providing educational opportunities for students in these fields including post-graduate and under-graduate teaching, and providing services and applications resulting from the reactor utilization. The research programs include topics in nuclear and solid-state physics, nuclear metrology, and radiochemistry, covering both fundamental questions and applied science. Most of the programs have strong ties to universities, other national research institutes and research laboratories. The Research Reactor Center takes its role very seriously as one of the major research reactor facility in the country providing educational opportunities to students in their programs related to nuclear sciences.

The scientific programs span several multidisciplinary, fundamental and applied research areas. Specific research programs include nuclear structure study from beta and gamma decay of radioactive nuclei and nuclear reactions, nuclear and neutron metrology, neutron diffraction and neutron multiple-diffraction study for crystalline and magnetic structure determination, perturbed -angular correlation (PAC) using radioactive nuclear probes to study the nuclear hyperfine interactions in solids and neutron activation analysis, both instrumental as well as involving radiochemical separation applied to the fields of health, agriculture, environment, geology and industry. The research in the areas of applied physics includes neutron radiography and instrumentation.

We firmly believe that no matter how much important the academic research may be in its own right, it doesn't do much good if it does not makes its way to the outside world somehow. The Research Reactor Center at IPEN is making enormous effort to enlarge the scope of services and applications resulting from reactor utilization so that more and more benefits of these applications could be offered to the society. Some of the products and services offered by the Center find their way to petroleum industry, aeronautical and space industry, medical clinics and hospitals, semiconductor industry, environmental agencies, universities and research institutions. We produce special radioisotopes ⁴¹Ar and ⁸²Br for industrial process inspection, ¹⁹²Ir and ¹⁹⁸Au radiation sources for brachytherapy, ¹⁵³Sm for bone cancer pain relief, calibrated gamma sources of ¹³³Ba, ¹³⁷Cs, ⁵⁷Co, ⁶⁰Co, ²⁴¹Am, ¹⁵²Eu used in clinics and hospitals practicing nuclear medicine as well as in the research laboratories. We offer routine services for the nondestructive testing by neutron radiography, multi-element trace analysis by NAA and irradiation of silicon crystals for neutron transmutation doping with phosphorus. The Research reactor Center offers training and re-training courses for the research as well as power reactor operators in the country.

Aiming at the local production of ⁹⁹Mo, precursor of the radioisotope ^99mTc, widely used in nuclear medicine, IPEN has invested considerable effort, during the last several years, to upgrade the power level of the reactor to 5MW. For this purpose several modifications in the reactor systems had to be implemented. It is planned to operate the reactor at 5 MW from January of 2003 and gradually increase the operation schedule from the present 64 hours to 120 hour continuous per week.

Neutron Radiography and Radioscopy with the SLOWPOKE-2 Reactor at RMC.
L.G.I. Bennett, W.J. Lewis, T.R. Chalovich and O. Francescone
SLOWPOKE-2 Facility at RMC
Department of Chemistry and Chemical Engineering
Royal Military College of Canada
Kingston, Ontario, Canada

Abstract
The neutron radioscopy system (NRS) installed on the SLOWPOKE-2 research reactor at the Royal Military College of Canada is being used to reveal water ingress in the flight control surfaces of the CF188 Hornet aircraft. The NRS consists of a neutron beam tube (NBT) in the reactor pool, which provides a near vertical beam ending in a shielded beam stop arrangement in the reactor room. With the component placed in a horizontal position between the NBT and the beam stop, water in the honeycomb cells can be easily detected, as can hydration of the adhesive and corrosion effects. The imaging position in the beam stop can accommodate either a vacuum cassette containing a 14"x17" film (neutron radiography) or a 17" square scintillation screen followed by a CCD camera for direct computer imaging (neutron radioscopy). Because of the relatively low neutron flux at the image plane for this small reactor, neutron radiography is performed with a medium speed film for an exposure time of about 20 minutes and neutron radioscopy in about five minutes. Thus, for efficiency, the inspection protocol is to scan the component, some of which are quite large, using neutron radioscopy, followed by neutron radiography of the affected areas.

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Fission-Track Dating of Minerals.
M. Balcázar and A. López.
Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, México D F 11801, México.

Abstract
The uranium trapped by minerals during its formation gives the possibility of determining the age of creation, or the age of its last heating event. Uranium atoms in the mineral naturally decay by spontaneous fission creating latent tracks which are visible under an optical microscope after an etching process. The number of spontaneous tracks is proportional to the ²³⁸U content in the mineral and the time that this uranium has been present. The uranium content is determined by irradiating a portion of the mineral in a research reactor to induce fission in the ²³⁵U. The induced and spontaneous fission tracks allow the age determination. The results of two minerals are presented: Apatite and Zircon. Apatite from the Cerro de Mercado, Durango, Mexico is internationally considered as a standard; Zircon has a very high uranium content and is specially suited for a low neutron flux. Apatite is also used to determine the thermal history of mineral deposits.

The Role of Small Research Reactors in Developing Countries: the Syrian Perspective.
I. Khamis.
Atomic Energy Commission, Syria.

Abstract
Research reactors have been accepted as an important tool of many nuclear centers and laboratories. Usefulness of research reactors depends mainly on its versatility and power. However, the most productive work using research reactors arises from the interdisciplinary nature of research reactors where many disciplines co-operate together such as chemistry, medical research, reactor and neutron physics...etc. Nuclear research reactors are generally classified, based on their neutron flux, into small, medium, high, and very high power reactors. MNSR with maximum thermal neutron flux of factors of 1012 n.cm-2.s-1 is considered of the first category, whence, it has derived its name miniature neutron source reactor. The main utilization of MNSRs is Neutron Activation Analysis (NAA), training and small scale radioisotope production. MNSR, very much similar to the Canadian SLOWPOKE, is considered as an excellent tool for the starting point in the nuclear program for developing countries. Being inherently safe, simple, reliable, and most of all poses no harm to the environment, it can be built at research institutions, hospitals, universities and training centers located in dense populated areas. This paper will focus on the advantages and disadvantages of having MNSR type reactors during the initial stages of a nuclear program in developing countries. Emphasis will be made on manpower requirements and development, efficient utilization, and enhanced know-how build up. A conclusion will be drawn to the future of such small reactor within basic requirements necessary for sustainable operation and utilization in developing countries.

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