Photonuclear production of ²⁸MG(→²⁸AL)

Abstract

The radionuclide 28Mg ( t 1~ = 20.9 h) decays by p-, yemissions (E 0.46 MeV, E+ = 0.031 i95 %), 0.400 (36 %), 0.942 (36 %), 1.342 (54 %) MeV) to the shor&lGed radioactive daughter Next to 7Mg (t1/2 = 9.9 min), 2*Mg is ?he longest-lived radionuclide of magnesium and therefore of considerable interest as a tracer, notably for physiological investigations (1,2). However, wide-spread application has been hampered by its restricted availability. This is because of difficulties encountered in its production due primarily to 28Mg being neutron-rich and fairly far from the line of p-stability.For its production both neutron and charged particle induced reactions (5-9) have been tested. Neutron irradiation of LiMg alloys in a nuclear reactor can produce some tens to hundreds of pCi's by way of the sequential processes 6Li(n,a)t/26Mg(t,p)2gMg, but the final product is of low specific activity (3). A routine procedure for a no-carrier-added product of high specific activity uses a 150 MeV a particle beam for the reaction 27Al(01,3p)~8Mg yielding batches of a few mCi after 6 hours of bombardment (8).Photonuclear production via the reaction 3oSi(y,2p)28Mg has been investigated earlier by others, who reported yields of 20 pCi of 28Mg using high-energy Bremsstrahlung generated by a 60 MeV e-beam (6).There is an on-going effort to explore the potential of the 500 MeV e-linac of our Institute for producing certain radionuclides of interest for application. The inherent problem associated with this kind of work is the necessity to have bulky targets in order to cope with the high penetrating power of Bremsstrahlung and the low cross sections of photonuclear reactions. We recently reported on the production of 67Cu using a low energy beam (Ee-I 140 MeV) (10). The production of BMg is considered a test case for production at the high energies available, notably at the site where the waste beam of physics experiments is dumped.To this end we measured photonuclear cross sections of a number of production reactions, studied targetry problems and designed procedures for the chemical separation of BMg from the bulk of target material (several tens of grams) and for its final purification. Cross sections (0,) measured are compiled in Table 1. 8A1 (tl13= 2.241 min, E = 2.86 MeV, E = 1.779 (100 %)). Argon has the disadvantages of having a very low cross-section as well as providing a low-density target if gaseous. Notwithstanding its low cross section phosphorus is still preferred over silicon as aptential target. One reason is that the 100 % natural isotopic abundance of 3lP versus 3.09 % for OSi overcompensates the lower cross section of 31P by a factor of about three in yields. Another reason is that some phosphorus compounds allow for elegant and more efficient target chemistry.

Magnesium transport between carp and water studied with 28Mg2+ as radiotracer

“…It was produced either by irradiation of Li-M g alloys with thermal neutrons in the IRI nuclear reactor (van der Velden et al, 1989b) or by irradiation of PC13 with high energy bremsstrahlung obtained from the N IK H E F 500 MeV electron linear accelerator (Polak et a l, 1989). In both cases the irradiation was followed by separation of magnesium from irradiated material leading to aqueous solutions of MgCl2 containing " Mg24-and its decay product 28A13+.…”

Separation of 28Mg from Reactor-Neutron Irradiated Li-Mg Alloy and Redetermination of its Half-life

“…However, contrary to the expectations, the application of 28 Mg in scientific research has not become a really common practice, not even in the life sciences, although magnesium is an essential element for all living organisms [8], This is mainly due to the scarcity of 28 Mg caused by the difficulties in producing practical quantities of this radionuclide either by thermal neutron induced reaction [3, 4, 9 -15] or by other nuclear reactions (e.g. by charged particle [2,5,7], fast neutron [6] or photon [16,17] induced reactions) and subsequent elaborate i.e. lengthy radiochemical separations.…”

Radiochemical Research with the Linear Electron Accelerator MEA

“…As a consequence, special radiochemical techniques have to be developed to be able to recover any particular radionuclide wanted. An example of a straightforward method is the production and recovery of the radionuclide 67 Cu (fi/2 = 61.8 h) from tens of grams of irradiated zinc oxide [8]. The reactions which contribute to the formation of 6 7 Cu are 68 Zn (7,p) 67 Cu and to a lesser extent 67 Zn (γ, p2n) 67 Cu.…”