Authors:Árpád Bihari, Zoltán Szűcs, Magdolna Mogyorósi, and Tamás Pintér
The low- and intermediate-activity level liquid wastes produced by the Paks Nuclear Power Plant (NPP) contain routinely measureable
gamma-emitting (e.g., 54Mn, 60Co, 110mAg, and 137Cs) as well as many so-called “difficult-to-measure” radionuclides. Despite of their low specific activity compared to the
total, the reliable determination of these radionuclides is an important issue of nuclear waste management. The increasing
amount of waste samples to be qualified yearly by our laboratory put a pressure on revising the existing procedure of 99Tc separation applied. We have managed to halve the initial amount of the sample required to achieve the same level of detection
of technetium. Furthermore, one of the new purifying steps introduced have proved to be able to separate 108mAg (and 110mAg) better than 99% keeping the 99Tc content of the product almost intact. Means of separation of 99Tc from 106Ru and 124+125Sb have also been successfully investigated. As intended, this new procedure has a major impact on the chemical reagent as
well as the electricity requirement of the separation making it more cost-effective.
Authors:H. Vinšová, V. Jedináková-Křížová, and M. Ožanová
99Tc is a redox active radionuclide, which is present as contaminant at a number of sites where nuclear fuel cycle operations
have been carried out. The aim of our research was study of bentonite interaction with Fe and Fe2+ cation and these influences on the
migration behavior. Radioanalytical and analytical methods were used for the concentration and chemical forms of 99Tc determination. It was found that Fe2+–Ca2+, Mg2+ ion exchange should be considered as a process of reaction among the corrosion products of carbon steel container and bentonite
in the environment of radioactive waste repository.
The analysis of99Tc was carried out in filter, peat and rainwater samples. A solvent extraction technique was used to separate Tc from them, where tributylphosphate was the extracting agent. Radiochemical yield was obtained by using99mTc as an internal tracer. A typical value of 60% was found for it. However, problems encountered in its determination are discussed in the text. Additionally, rainwater samples were analyzed for137Cs. This was adsorbed in ammonium phosphomolibdate. Radiochemical yield was obtained by using134Cs as an internal tracer.
Authors:J. Hattink, L. Weltje, H. Wolterbeek, and J. de Goeij
This study deals with the accumulation dynamics of the long-lived fission product technetium (99Tc) in duckweed. Duckweed serves as model for aquatic plants, because of its representative foliar uptake for 99Tc. This study shows that 99Tc is irreversibly accumulated and distributed over cytoplasm, chloroplasts and mitochondria. Autoradiography showed that 99Tc was not transported to new biomass. Irreversible storage of 99Tc in plant biomass means that steady-state situations cannot be interpreted as a balance between uptake and elimination of 99Tc, but that 99Tc continuously builds up in each single duckweed plant and overall Tc concentrations are averaged over new biomass.
Authors:T. Sekine, K. Yoshihara, Zs. Németh, L. Lakosi, and Á. Veres
A new nuclear excitation process,99Tc (,
)99mTc reaction, was applied for the first time to radioactivation analysis of technetium. Bremsstrahlung irradiation of99Tc samples gave the reaction product99mTc which emits -ray measurable with ease by a semiconductor detector. The production rate of99mTc per g99Tc was linearly correlated with the flux of bremsstrahlung. The detection limit of99Tc was estimated to be nanogram order (0.63 Bq99Tc) under the optimum irradiation condition. Possible interference by100Ru(, p)99mTc reaction was also studied, which could be discriminated from the (,
) reaction by simultaneously occurring98Ru (, p)97Ru reaction.
A simple technique using a combination of cation exchange and solid phase extraction chromatographic resins has been developed for the separation of99Tc from other radionuclides present in nuclear fuel leachates. Quantification of the isolated99Tc is accomplished using liquid scintillation counting. The method provides consistently high recoveries (>96%), generates small amounts of waste compared to classical methods, and requires less analysis time.
Authors:J. McAninch, A. Marchetti, B. Bergquist, N. Stoyer, G. Nimz, M. Caffee, R. Finkel, K. Moody, E. Sideras-Haddad, B. Buchholz, B. Esser, and I. Proctor
Accelerator mass spectrometry (AMS) is an established technique for the detection of long-lived radionuclides at environmental
levels. At LLNL, planned facility upgrades and advances in detection techniques are allowing us to explore the applicability
of AMS to isotopes not previously pursued. One such isotope is99Tc. We have performed a number of preliminary tests to examine the technical feasibility of AMS for the detection of99Tc. The questions addressed were negative ion production in the cesium sputter source, transport efficiency for the ions through
the spectrometer, and detection efficiency for99Tc ions after the spectrometer. Based on the positive results of these tests, we have begun to develo measurement protocol.
Authors:E. Holm, J. Rioseco, S. Ballestra, and A. Walton
A method of99Tc determination has been developed based on sample decomposition followed by purification from interfering elements by hydroxide and oxide precipitations. Technetium is extracted by TBP and electrodeposited onto stainless steel discs from sodium hydroxide solution.99Tcm is used as yield monitor. The method has been applied to study releases from different sources and contents in different samples of atmospheric, terrestrial and marine origin. Results show enhanced99Tc/137Cs activity ratios for samples collected in recent years which are only expected to be contaminated from fallout from nuclear tests. Integrated fallout measurements did not reflect these enhanced ratios.
Authors:N. Momoshima, M. Sayad, M. Yamada, M. Takamura, and H. Kawamura
Global fallout levels of 99Tc and 137Cs of surface seawater in the Pacific Ocean were measured. The 99Tc concentrations ranged from 0.62 to 3.33 mBq. m-3and 5 of 6 samples showed less than 1 mBq. m-3except one sample taken in the Great Barrier Reef, Australia. The 137Cs concentrations ranged from 2.13 to 3.14 Bq. m-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The 99Tc/137Cs activity ratios ranged from 2.5. 10-4to 2.9. 10-4, which is very close to that calculated theoretically from the fission yield.
Authors:M. Chatterjee, S. Bhattacharyya, A. Bhattacharyya, M. Banerjee, G. Muthukrishnan, and S. Banerjee
A method is described for the recovery of NH499TcO4 from its reaction waste. From the collected waste solution99Tc was precipitated as99Tc2S7 which on digestion with ammoniacal hydrogen peroxide produced a mixture of NH499TcO4 and (NH4)2SO4 from which the latter was removed by treatment with Ba(OH)2. The solution fumished NH499TcO4 as a crystalline material in 54% overall yield and with 96–98% purity after chromatographic purification over Dowex 50W column. Recrystallisation of this material from aqueous ammoniacal ethanol gave the analytical material which compared well with a standard sample and with literature data in terms of its -counts/mg and its molar extinction co-efficients () at 244 and 286 nm.