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TEXTURAL AND FLUID PHASE ANALYSIS OF ROCK SALT SUBJECTED TO THE COMBINED EFFECTS OF PRESSURE, HEAT AND GAMMA RADIATION

Objective

PREVIOUS STUDIES HAVE SHOWN THAT RADIOLYTIC PROCESSES INDUCED BY IRRADIATION OF SALT CREATE THE MIGRATION OF FLUID PHASES AND THE FORMATION OF DEFECTS IN THE CRYSTAL LATTICE, I.E.: DETACHMENT OF SODIUM IONS WHICH CLUSTER TOGETHER FORMING COLLOIDAL SODIUM. THE FORMATION OF COLLOIDAL SODIUM GIVES RISE TO STORED ENERGY, WHICH CAN BE RELEASED BY RECOMBINATION OF THE COLLOIDS WITH THE TRAPPED CHLORINE. THE TEMPERATURE RISES CREATING, ACCORDING TO THIS RELEASE, THE MAIN CONCERN OF IRRADIATION DAMAGE WITH RESPECT TO THE SAFETY ASPECTS OF NUCLEAR WASTE BURIAL.
DUE TO DIFFERENCES IN POTENTIAL ENERGY BETWEEN NEIGHBOURING CRYSTALS, GRAIN BOUNDARIES TEND TO MOVE AT THE COST OF THE MOST ENERGETIC CRYSTALS; THIS RECRYSTALLIZATION PROCESS, ENHANCED BY THE PRESENCE OF BRINES, CLEARS THE CRYSTAL FROM IRRADIATION DAMAGE.
THE MAIN GOAL OF THE PROJECT IS TO CALCULATE THE ABOVE-MENTIONED PHENOMENON, USING THE JAIN-LIDIARD THEORY, IN HETEROGENEOUS AND IMPURE MATERIAL, SUCH AS ROCK SALT, WHEN EXPOSED TO DIFFERENT DOSE-RATE, TEMPERATURE AND TIME OF IRRADIATION.
THE RESEARCH WORK IS BEING DONE IN COOPERATION WITH THE NETHERLANDS ENERGY RESEARCH FOUNDATION (ECN), THE UNIVERSITY OF UTRECHT AND THE UNIVERSITY OF BARCELONA. THE IRRADIATION WILL BE CONDUCTED AT THE HAW TEST FIELD AT ASSE (FRG) AND AT THE HFR IN PETTEN (NL).
The formation of colloidal sodium by radiolytic processes is a main concern with respect to the safe disposal of high level radioactive waste in salt formations. The research work sought to assess the irradiation damage in natural rock salt when exposed to a different dose, dose rate, temperature and time of gamma irradiation.
The work encompassed 4 major tasks: firstly detailed characterization of both solid and fluid phases of natural rock salt; secondly, gamma irradiation of salt samples; thirdly, determination of the amount of colloidal sodium present in irradiated samples; and fourthly, calculation of radiation damage.
1. SAMPLING OF SALT SPECIMENS FROM SPANISH SITES AND THE HAW TEST FIELD; PREPARATION OF SYNTHETIC POLYCRYSTALLINE AND HARSHAW SAMPLES.
2. CHEMICAL, PETROLOGICAL AND MINERALOGICAL CHARATERIZATION OF THE VARIOUS SALT SAMPLES. SOLID AND FLUID PHASE DETERMINATION, CHEMICAL EVOLUTION FROM STEP HEATING AND MICROSTRUCTURAL ANALYSIS.
3. TEXTURAL ANALYSIS OF UNDISTURBED SAMPLES.
4. PREPARATION OF SAMPLES AND PRESSURIZED CONTAINERS FOR THE IRRADIATION PHASE.
5. IRRADIATION OF 180 SAMPLES IN THE HAW TEST FIELD AT ASSE. SAMPLES WILL BE IRRADIATED FROM 6 MONTHS TO 5 YEARS AT DIFFERENT DOSERATE AND TEMPERATURE, IN PRESSURIZED CONTAINERS WITH DIFFERENT BRINE CONTENTS.
6. IRRADIATION OF SOME SALT SPECIMENS AT THE HIGH FLUX REACTOR (HFR) (PETTEN).
7. POST-IRRADIATION ANALYSIS TO INVESTIGATE THE AMOUNT STORED ENERGY AND THE VARIATION IN CHEMICAL COMPOSITION, WATER CONTENT AND MICROSTRUCTURE.
8. THEORETICAL CALCULATIONS ON THE BASIS OF THE JAIN-LIDIARD MODEL, OF THE DAMAGE WHICH COULD BE EXPECTED BY IRRADIATION AND HEATING.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

EMPRESA NACIONAL DE RESIDUOS RADIOACTIVOS S.A.
Address
7,Emilio Vargas 7
28043 Madrid
Spain

Participants (1)

GSF
Spain
Address

Barcelona