Basu, D

Bhattacharyya, S N

Das, N R

English

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Indian J. Pby». 6SA (6), 579-581 (1991)Charged particle activation analysis of niobium in geological matrixN R Das, D Basu and S N BhattactiaryyaSaha Institute o f Nuclear Physics, 1 1fiSF, B idhannagar.C a lc u tta -7 0 0 0 6 4 , IndiaA bstract: On a lpha-partic le  activation o f traces o f n iobium , preconcentrated  from some specific  varieties  o f phospSate rocks, w ith  a 4 0  M e V  alpha beam from  th e  V ariab le  Energy C yc lo tron , d ifferah t radionuclides, nam ely. ""Tc. • '" •T c , ” *Tc, •■*""Tc, ”*Tc  and ' * " ‘Tc, form ed by th e  nuclear reactions, (« , n ), (< , 2n ), (< , 3n) and (< , i<n} w ere  detected. The fe d iib ility  of u tilisa tion  o f more than one isotope formed at d ifferen t depths of th e  th ic k  target m atrix has been critica lly  investigated.Keywords : A c tiv a tio n  analysis, n iob ium , preconcentration, geological m aterial. PACS No : 82.80.Jp, 93.85.+qI. IntroductionGeological materials are complex heterogeneous mixtures of minerals which vary widely in composition and are often fine grained. Generally such materials are mechanically incompetent for use as self-supporting sections. Therefore it is almost impossible to prepare thin samples that could be used to minimize back­ground radiations and maximise trace element sensitivity. Besides non-nuclear techniques like X-ray fluorescence (Giauque et al 1986), atomic absorption (Donaldson and Leaver 1990) and optical spectroscopy, neutron and photon activation analysis (Yoshioka et al 1988) have been applied w ith considerable success. In recent years, accelerator based nuclear or atomic techniques are being developed to investigate such problems. Thus particle induced X-ray emission or the complementary method of particle induced gamma emission (Brissaud et al 1986) are used for such analysis. In some cases direct charged particle activation analysis (Barrandon 1986) can give very high sensitivity. However the efficiency of CPAPA depends on various parameters such as nature of the projectile, characteristic nuclear properties of the target, the target matrix, etc.Trace of tantalum in some specific varieties of phosphate rocks had been determined through neutron activation analysis (Das and Bhattacharyya 1980,1982) following a separation procedure developed earlier. Possible existence of niobium in the sample could not be established since this element is not amenable to NAA. On the other hand the excitation functions (<, xn) reactions of niobium 17 679580 N R Das D 5asu and S N  Bhattacharyya(Ramamoorthy et al 1986) indicate fairly high cross sections for the production of technitium isotopes of suitable half lives w ith an energy range of about 40  MeV for the projectiles. W ith this background, an attempt was made to utilise more than one radionuclides produced by alpha activation of traces of niobium in a suitable matrix bombarded by 40 MeV <-beam at Variable Energy Cyclotron Centre, Calcutta.2. ExperimentalPhosphate rocks originating in the District of Purulia, West Bengal, were supplied by the West Bengal Mineral Development and Trading Corporation, Traces of niobium in the rock samples were preconcentrated in A ljO s following a chemical procedure developed earlier. The samples were encased w ith aluminium foils and irradiated with an alpha beam of 40 MeV under specific experimental conditions at Variable Energy Cyclotron Centre, Calcutta. A HPGe detector in conjunction w ith  a ND 65 8 K multichannel analyser was used for monitoring the radioactive products formed in the target matrix by alpha irradiation.3. DiscussionUnlike neutrons or photons, charged particles of several MeV energy are completely absorbed within a range of several microns of a thick target sample producing different reactions at different layers w ith varying cross sections. Analysis of the irradiated samples indicates the formation of different radionuclides such as ""Tc, " '"T c , *®Tc, ®*"'Tc, ®*Tc and ®*” Nb produced by different nuclear reactions in the experimental matrix in a single run (Das et al 1987). However, the end product of each of the three reactions, (<, n), («c, 2n) and (< , 3n), namely, ®*Tc, “*Tc and ®*Tc were used quite independently for quantitative estimation of traces of niobium distributed uniformly in the target material. Results obtained for different isotopes are shown in Table 1.Table I. D eterm ination  of n iob ium  in a phosphate rock sample through d ifferen t nuclear reactions.NuclearreactionSelectedgammaenergy,keVH a lf life  T 1 /2Concentra­tio n  of niob ium , ppm“»Nb (<, 3n) » 'T c 7 0 2 .7 2 93  m 2 .9"*N b  ( * .  2 n ) “‘ Tc 7 6 5 .9 2 0  h 3.1“ Nb {1 , n) ""Tc 7 7 8 .2 4 .3  d 2 .9The isotopes utilised for determination of niobium such as "*Tc, ®*Tc and ®*Tc have been characterised by several gamma rays. However, the gamma rays were selected on the basis of their relative intensity as well as freedom from any serious interference from neighbouring gamma rays.The other irradiation products from niobium such as “ ‘ “Tc, ®*™Tc and ‘**®Nb having either short or too long halflives are somewhat difficult to utilise forCharged particle activation analysis etc 581analysis of niobium because of some overlapping of common gamma energies as well as presence of some interfering lines due to some contaminants. The characteristic energy regions were calibrated by the technitium isotopes produced by alpha irradiation of pure niobium foil under identical conditions.The results obtained through individual reactions are in good agreement with each other. The consistency of the data indicates the efficiency and reliability of CPAA in the determination of niobium even in ppm level in geological materials.R eferencesBarrandon J N 1986 NucI, Instrum . M eth. B I 4 133 .Brissaud I, A de ChSteau Thierry, Frontier JP  and Lagarde G 1 9 8 6  J, Radioanol. N ucI. Chem, A rtic les  10213Das N R and Bhattacharyya S N 1980 In t .J .  Appl. Radint. Isotope. 31 652 ----- 1982J , Radioanal. Chem. 68 75Das N R, Basu D and Bhattacharyya S N 1987 In t .J .  ^ P l -  Radiat. Isotope. 38 Part A 939 Donaldson E M and Leaver M E 1990 Talanta  37 173 Giauque R D, Jaklevic J M and Thonrpson A C 1986 Anal. Chem. 54 940 Ramamoorthy N, Das M K, Sarkar B R and Wlani R S 1986J. Radioanal. Chem. 9 8 121 Yoshioka A, Nomura Takeya M, Shimura Masumoto K and Myagi M 1988/. Radioanal. Chem. Artic/es 122175

Charged Particle Activation Analysis of Niobium in Geological Matrix

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Charged Particle Activation Analysis of Niobium in Geological Matrix

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