EPR signal enhancement of alanine-boron dosimeters irradiated with gamma-neutron mixed fields

NADIA ÁLVAREZ; GABRIELA ALEJANDRO; A. BUTERA

Buenos Aires

Congreso; I Congreso Argentino de Técnicas Neutrónicas; 2017

EPR signal enhancement of alanine-boron dosimetersirradiated with gamma-neutron mixed fieldsN. Álvarez(1)*, G.Alejandro(1), A. Butera(1)(1) Laboratorio de Resonancias Magnéticas -Instituto Balseiro - Centro Atómico Bariloche, Bariloche, Argentina.*nadia.alvarez@cab.cnea.gov.arThe aminoacid l-a-alanine is widely used for electronand gamma-ray dosimetric purposes. The ionizing radiation produces stable defectsin the alanine and are therefore suitable as radiation sensors. The presence ofthese defects (generally free radicals) can be sensed in a non-destructive waywith the Electronic Paramagnetic Resonance (EPR) technique, which has beenlong-widely used to estimate doses in radiological emergencies, as well as intherapeutics and in industrial processes with ionizing radiation. Thewidespread use of alanine in biomedical applications is due to its tissueequivalent properties which minimizes the corrections in the determination ofthe received dose.In the case of photons and electronsthe radiation has enough energy to break a chemical bond and generate a freeradical (essentially a ½ spin) whose EPR signal depends on the interactionswith the surrounding chemical environment. In the case of thermal neutrons, thegeneration of the defect occurs indirectly. The sensitive material (in ourcase, alanine) is mixed with a strong neutron absorber (10B) whichby absorbing a neutron becomes unstable and decays to a lighter nucleus withthe emission of an alpha particle and gamma radiation. These energeticparticles are the ones that produce defects in the sensitive material, whichare then detected by EPR spectroscopy. We have synthesized and characterizedthe EPR response of an alanine-boron compound to be used in the case of a mixedradiation field (neutrons + photons). A sensor (alanine with boron) is designedto measure the total dose, differentiating both contributions. The compound wassynthesized by reacting the aminoacid alanine with boric acid in two different solvents:neutral and alkaline. Thesamples were irradiated at the Cobalt-60 gamma ray source in the PISI (Plantade Irradiación Semi Industrial) and with a neutron and photon mixed field at theBNCT facility in the RA-6 nuclear reactor at thermal neutron fluence ofapproximately 1.16 ´ 1013 n/cm2and 5.61 ´ 1012 n/cm2 measuredthrough the activation gold foils. The absorbed dose in dosemeters in thesamples irradiated at the PISI facilities are in the range of 100 Gy - 95 kGy. Thiswork presents preliminary results of the use of the alanine-boron compound as athermal neutron fluence detector. The technique used is the detection by EPR ofthe free radical yield upon thermal neutron irradiation. "I Congreso Argentino de TécnicasNeutrónicas" 15 - 16 de marzo 2017:Viernes 17: "Workshop CNEA/MinCyT: Fase II de instrumentación delLAHN"