Research related to radioactive waste

Studies on migration of radioisotopes

Studies on migration of radioisotopes in geological media are intended to furnish information on the perspectives for a possible repository site selection for high level nuclear waste in the future. The Boda Claystone Formation was selected in a preliminary experts' evaluation as a possible candidate for waste site in Hungary. This formation is located in the Mecsek Mountains, south-west Hungary. An underground research laboratory was established and had been in operation in 1994 - 1999. Several drills were driven from here, most of our samples originated from these borecores. The method used is the break-through measurement. There are two compartments in a cell separated by the studied sample (a slice cut from the borecore of the rock). One compartment is filled with ground water containing the isotope in anionic form, and the activity of the ground water is regularly measured in the other compartment. After a while ( > 100 days) the isotope diffuses through and its activity starts to increase.

With these breakthrough measurements we participate in the EU FP-6 FUNMIG (Fundamental Processes of the Radionuclide Migration) Integrated Project.

Transmutation of long-lived nuclear wastes by spallation reactions

Spallation is a nuclear process, known from 1947 in which a high-energy particle (p,xn), (γ,xn), in GeV energy range, impinging on a heavy target produces a large number of neutrons and some other particles. Typically a 1 GeV proton on a heavy metal (U) produces ~ 30 neutrons. The extra neutrons provided by the accelerator allow maintaining the chain reaction while burning the long-lived nuclear waste.

As any nuclear procedure involves a radiation burden to the operators, it is appropriate to apply conditions for partitioning and transmutation techniques, which minimise environmental impacts apart from other technical considerations. One of this is the subcritical assembly, which is a reactor-like system, but unlike a conventional nuclear reactor in which fission goes on in a chain reaction without supply of external neutrons, a particle accelerator beam produces these neutrons when it is incident on a suitable target located within the assembly. The most important advantage of the accelerator driven system (ADS) is that if the accelerator is switched off the subcritical reactor comes to a standstill, thus the very hazardous runaway accidents can be avoided and isolation of radioactive material from man and the environment can be ensured. We investigated the (γ,xn) reactions cross sections of 99Tc and 129I in the threshold and below (5-50 MeV) spallation-energy range. We studied the above-mentioned programs and its possibility in the nuclear waste insinerate programs.

  1. T. Sekine, K. Yoshihara, J. Sáfár, L. Lakosi, Á. Veres, 95Tc and 99Tc production by (γ ,xn) reactions, Journal of Radioanalitical and Nuclear Chemistry Letters 186, 165, (1994)
  2. J. Sáfár, L. Lakosi, Á. Veres, T. Sekine, K. Yoshihara, "Photoexcitation of metastable states in 111Cd, 113In and 115In in the 5-30 MeV energy range". Proceedings of the 8th Int. Symp. on Capture Gamma-Ray Spectroscopy and Related Topics, Fribourg, Switzerland, Sept. 20-24, 1993, J. Kern, Ed. (World Scientific, Singapore, 1994) pp. 629-631
  3. Veres Á., Lakosi L., Sáfár J.: Nukleáris hulladékok átalakítása fékezési sugárzással, Fizikai Szemle, No.11, 399 (2000)
  4. Veres Á. Hosszú életü nukleáris hulladékok átalakítása és hasznosítása, Magyar Tudomány 2001/11, 1324 (2001)
  5. Veres Á., Hogyan szabadulhatunk meg a nukleáris hulladékoktól? Egy új módszer: a spalláció, Természettudományi közlöny 134. évf. 4. füzet 179 (2003)
  6. Á. Veres, "Transmutation of long-lived nuclear vastes by spallation reaction and its radiotracer consequences" pp392-404, in Interface Sciences and Technology, Volume 3 "Radiotracer Studies of Interfaces", Ed. G. Horányi, Elsevier Academic Press (2004)