Aerosol penetration of leak pathways : an examination of the available data and models.

Abstract

Data and models of aerosol particle deposition in leak pathways are described. Pathways considered include capillaries, orifices, slots and cracks in concrete. The Morewitz-Vaughan criterion for aerosol plugging of leak pathways is shown to be applicable only to a limited range of particle settling velocities and Stokes numbers. More useful are sampling efficiency criteria defined by Davies and by Liu and Agarwal.

Fission Product Release and Transport

“…[153] with permission from Elsevier.) Except for daughter FPs, that is, products with a parent radionuclide that has a higher or equivalent half-life such as 140 Ba/ 140 La, 132 Te/ 132 I, and 95 Zr/ 95 Nb for which the activity variation of the daughter product is also related to that of the parent. Except for daughter FPs, that is, products with a parent radionuclide that has a higher or equivalent half-life such as 140 Ba/ 140 La, 132 Te/ 132 I, and 95 Zr/ 95 Nb for which the activity variation of the daughter product is also related to that of the parent.…”

“…Nonvolatile FPs remain associated with the fuel ( 239 Np and 140 La in the short term, and 95 Zr/ 25 Nb and 144 Ce in the medium and long term). Owing to the decay heat that continues to be released, they can heat and melt the core if the latter is not cooled sufficiently.…”

“…Table 5.2 lists the main radioactive FPs and specifies their scope of action in the short, medium, and long term, as well as their degree of volatility. The significant contribution of volatile FPs in the short term comes from the iodine isotopes and lanthanide isotopes (in green), which cover a longer half-life owing to 140 La. This variation decreases very quickly in time: it represents about 5% of the total reactor power at the time of shutdown, and then only 1% after one hour and 0.1% after one month.…”

“…Figure 5.5 (drawn from the VERCORS 5 test [9], [10]) illustrates these four categories: l volatile FPs (represented by 137 Cs); l semivolatile FPs (represented by 140 The first category includes uranium and neptunium whose releases can reach 10% before the fuel melts.…”

“…From the VI-4 series onward, an additional online gamma [155], [156]). The first program in particular revealed the very high release of ruthenium in air, including at low temperatures of about 1000-1500 C. Certain tests on cladding-free fragments have also revealed the very high volatilization of the fuel at high temperature and under extremely oxidizing conditions, associated with a high release of very lowvolatile or nonvolatile FPs, via a "matrix stripping" process: 50% for 95 Nb and 140 La, and 30% for 95 Zr. This program provided highly representative results on the release of FPs, but only in relation to long-lived FPs (mainly 85 Kr, 106 Ru, 125 Sb, 134 Cs, 137 Cs, 144 Ce, and 154 Eu) as the samples were not re-irradiated prior to the tests.…”