Stability of organic compounds

Much progress has been made in determining the relative importance of fast neutrons, gamma rays or electrons, temperature and dose rate on the stability of organic compounds. Most of the data were obtained on terphenyls. The stability of hydroterphenyls (HB-40) was described by Canada and Spain. A brief description of the stability of petroleum fractions was also presented by France (PL-194/24). The decomposition kinetics have been traditionally expressed in the form dC = kR Cn dτ + kp Cm dt, where C concentration of the component being degraded, wt. fraction, kR is the radiolysis rate constant, g W-1 h-1; kg = pyrolysis rate constant, h -1; τ radiation dose, Wh g-1; t = time, h; n, m = constants representing the kinetic order of the reaction. This of course assumes that radiolysis and pyrolysis produce additive effects on the total degradation, and that there is a simple kinetic order. From this equation the conventional 'G' value (molecules converted per 100 eV energy absorbed) are found by G -11.65 dC/ dτ. From the papers mentioned here are PL-194/19 and PL-194/24, of which abstracts are given in Section III, one can conclude that: most of the information required to assess coolant consumption rates is now available; further work is required to define more clearly the kinetics and mechanisms of radiolysis and radiopyrolysis in the temperature range above 350 deg. C, for an operating reactor; there is also a need for further confirmation of methods for predicting the total dose absorbed in the coolant in an operating reactor, to allow reasonable assessment of the total coolant consumption rates