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_TION OF ALANINE AS AN ACCIDENT DOSIMETER AND INTERPRETATION OF DOSE-EFFECT RELATIONSSHIPS BY MODEL DESCRIPTION

Objective

ALANINE, WHICH IS A SIMPLE AMINO ACID, IS A VERY VERSATILE DOSIMETRIC MATERIAL WITH PROPERTIES CORRESPONDING TO AN IDEAL ACCIDENT DOSIMETER. UPON IRRADIATION FREE RADICALS ARE PRODUCED, WHICH ARE VERY STABLE IN TIME. THE PRODUCED FREE RADICALS ARE DETECTED BY ELECTRON SPIN RESONANCE SPECTROSCOPY, ESR, WHICH DOES NOT DESTROY THE SIGNAL ALLOWING THE DOSIMETERS TO BE KEPT FOR DOCUMENTATION PURPOSES. THE INTENTION OF THE PROJECT IS TO DEVELOP THE ALANINE DOSIMETER AS AN ACCIDENT DOSIMETER AND TO INVESTIGATE ITS PROPERTIES WITH RESPECT TO HIGH-LET RADIATIONS COVERING A BROAD RANGE IN LET AND PARTICLE ATOMIC NUMBER. OF PARTICULAR INTEREST IS THE ESTABLISHMENT OF EXPERIMENTAL DATA FOR HIGH-LET PARTICLES SIMULATING THE SECONDARY PARTICLE SPECTRUM FOLLOWING NEUTRON EXPOSURE.

THE PROGRAMME OF WORK IS:
A. THE ALANINE DOSIMETER IS INVESTIGATED WITH SPECIAL EMPHASIS ON DOSES BELOW 1 GY. AN INCREASE IN SENSITIVITY WILL BE ATTEMPTED THROUGH A DEUTERIZATION OF ALANINE BY WHICH PROCESS THREE MOBILE PROTONS ARE INTERCHANGED WITH DEUTERONS. THIS SHOULD LEAD TO A DECREASED LINE WIDTH OF THE ESR-SIGNAL AND THUS TO A HIGHER AMPLITUDE.
FOR REASONS OF HEAVY CHARGED PARTICLE IRRADIATIONS, WHICH CAUSES EXTREMELY HIGH DOSES IN THE TRACK CORE, ALANINE SHOULD BE INVESTIGATED FOR MATERIAL CHANGES AT HIGH DOSES. THE INVESTIGATION CONCERNS A POSSIBLE FORMATION OF NEW RADICALS AND THEIR STABILITY. THESE NEW RADICALS SHOULD MOST EASILY BE DETECTED IN SINGLE CRYSTALS IRRADIATED WITH FAST ELECTRONS OF HIGH DOSE RATE, AND IN WHICH THE SPECTRAL RESOLUTION IS OPTIMUM.
B. INVESTIGATIONS WILL BE PERFORMED ON A SUITABLE BINDING MATERIAL TO BE MIXED WITH PURE ALANINE FOR MAKING A MECHANICAL STABLE AND ROBUST PELLET. THE AMOUNT OF BINDING MATERIAL IN THE PELLET SHOULD BE OPTIMIZED IN RESPECT TO THE MECHANICAL STABILITY AS WELL AS TO YIELD THE HIGHEST RADIATION SENSITIVITY OF THE DOSIMETER. THE MECHANICAL STABILITY WILL BE MEASURED AS A STRENGTH PER UNIT AREA AT WHICH THE PELLET IS BEING CRUSHED.
THE BINDING MATERIAL SHOULD HAVE AN ESR-SIGNAL AMPLITUDE RELATIVE TO THAT OF ALANINE AS LOW AS POSSIBLE ALSO UPON IRRADIATION.
C. THE MECHANICAL PRESSING OF ALANINE TO FORM PELLETS HAS BEEN REPORTED TO PRODUCE RADICALS AND AS SUCH A BACKGROUND SIGNAL. AN ANNEALING PROCEDURE WILL BE EMPLOYED IN AN ATTEMPT TO ELIMINATE THIS SIGNAL.
D. INVESTIGATIONS WILL BE PERFORMED ON FADING OF THE ESR-SIGNAL WITH TIME AND ON SENSITIVITY OF RESPONSE TOWARDS HUMIDITY.
E. OPTIMIZING THE MICROWAVE POWER OF THE ESR-SPECTROMETER IMPROVES THE SIGNAL/NOISE RATIO. THE OPTIMUM POWER-SETTING IS TO A CERTAIN EXTENT A FUNCTION OF DOSE TO THE ALANINE PELLET.
OPTIMIZING THE MAGNETIC FIELD MODULATION OF THE ESR-SPECTROMETER IMPROVES THE FINE STRUCTURE OF THE ESR SPECTRUM AND YIELDS A NARROW SPECTRUM AND THUS A HIGHER SIGNAL AMPLITUDE.
F. ESTABLISHMENT OF DOSE-RESPONSE DATA FOR LOW-LET RADIATIONS OF 60 CO GAMMA-RAYS AND FAST ELECTRONS, AND OF HEAVY CHARGED PARTICLES COVERING A BROAD RANGE IN LET AND ATOMIC NUMBER, WITH EMPHASIS PUT ON CHARGED PARTICLES SIMULATING FAST NEUTRON SPECTRA IN TISSUE. DOSE-RESPONSE DATA WILL BE OBTAINED FOR ALANINE IRRADIATED WITH CYCLOTRON PRODUCED 5.6 MEV NEUTRONS AND WITH MIXED GAMMA AND NEUTRONS FIELDS. DOSE-RESPONSE DATA WILL BE OBTAINED FOR ALANINE IRRADIATED WITH VERY LOW ENERGY ROENTGEN PHOTONS AND ELECTRONS (E SMALLER THAN 50 KEV).

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

RISOE NATIONAL LABORATORY
Address
P.o. Box 49
4000 Roskilde
Denmark