Explosive decomposition of heavily irradiated NaCl

Abstract

In heavily irradiated NaCl explosions can be initiated during irradiation or later, after the irradiation, when the samples are heated to temperatures in the range 100-250°C. As a result of the irradiation Na and C12 precipitates, dislocations and voids are produced, along with stored energy (the maximum value observed until now N 76 kJ/mol, which is about 18.5% of the enthalpy of formation of NaCI, 411.2kJ/mol). This implies that heavily irradiated NaCl is a highly energetic material. We have observed that the samples, which revealed large radiation-induced voids, explode rather easily. In these samples the instability connected with large voids (hot spots) probably initiates the explosive release of stored energy, which is in many cases accompanied by characteristic (explosive) sounds. In this paper we will discuss the nature of the explosions and show that a basically stable insulating compound, such as NaCI, may become unstable after heavy irradiation.

Characterization of the size and orientation of Na and Cl2nanocrystals in electron irradiated NaCl crystals by means of synchrotron radiation

“…It is important to note here that the sizes of the radiation-induced Na and Cl 2 precipitates, obtained by means of the high-resolution x-ray diffraction experiments, are much larger than those estimated from earlier investigations with other techniques [1][2][3][4][5][6][7][8][9][10][11]. In contrast with the 'x-ray sizes' in the range of several hundred angstroms, presented in tables 1 and 2, the results obtained with the other techniques suggest that the average size of the precipitates is a few dozen angstroms, which means that there is a discrepancy of at least one order of magnitude.…”

New scenario for the accumulation and release of radiation damage in rock salt and related materials

“…1). The latter violent effects have been studied extensively during carefully executed annealing experiments [10], but we have also found strong evidence that explosion-drive fracture occurs during irradiation at very high doses. Our earlier experimental results, which have been discussed at length in [10] demonstrate very clearly that the observed explosive phenomena are driven to a large extent by instantaneous back reactions between colloidal Na and Cl 2 precipitates and cannot be explained by catastrophic cracking, which has been observed in insulators during implantation.…”

A model for void-induced back reaction between radiolytic products in NaCl

“…Note that real voids are not spherical [2][3][4], so the actual stresses can be higher than estimated by Eq. (13).…”

“…Irradiation of NaCl samples generates H and F centres, which are collected together to form chlorine bubbles and sodium colloids [1]. Our experiments [2][3][4] on different NaCl samples, heavily irradiated with 0.5 MeV electrons up to fluences of 6 Â 10 18 cm À2 , have shown that with increasing irradiation dose, voids are formed followed by explosion-like fracture of the material. We explain this by a back reaction between radiolytic products.…”