Modelling of the Dounreay Recovered Spent Nuclear Fuel Database
- PDF / 596,500 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 31 Downloads / 208 Views
CC6.4.1
Modelling of the Dounreay Recovered Spent Nuclear Fuel Database I.D. Baikie1, Frank Dennis, Massimo Scirea and Ron Crawford UKAEA, Dounreay, Thurso, KW14 7TZ, UK 1 KP Technology Ltd, Milton House, Thurso Road, Wick Caithness, KW1 5LE, UK ABSTRACT We report the initial results of modelling studies performed on the Dounreay Database of Spent Nuclear fuel particles recovered from the marine environment and coastal foreshore adjacent to the Dounreay Fast Reactor Complex located in the North East coast of Scotland. We demonstrate how interrogation of the fuel-particle frequency versus 137Cs isotopic distribution allows us to generate particle behaviour models and residence lifetimes of various particle subgroups. Similarly we find the recovered fuel particle's spatial distribution and shape characteristics are determined by environmental selection rules governed by properties of adjacent sediment and sediment transport mechanisms. Analysis of the Spent Fuel particle database allows us to speculate on the original Site discharge pathways and fuel composition at the time of discharge. Further such studies correlate well with other sample morphology and compositional data and allow us to speculate upon the ultimate fate of different spent fuel types. INTRODUCTION Over 1000 particles containing Spent Nuclear fuel have been recovered from the Dounreay Foreshore, Sandside Beach and the marine environment adjacent to the nuclear licensed site [1], an aerial view of which is shown in figure 1. The particles are mainly metallic in composition and have levels of radioactivity between 102 - 108 Bq. Materials analysis of a number of these particles [2-4] indicate that most of them are derived from two types of irradiated fuel: Materials Test Reactor (MTR) and Dounreay Fast Reactor (DFR). Gamma ray spectroscopy of the Caesium (Cs) isotopic content of some 20 particles suggests that the cooling time is (38 ± 3) years, indicating that they have been irradiated about 1966 [1]. The current knowledge of the particle pathways to the environment indicates that the most likely route was through a low active drain which discharged effluent to the sea via a diffusion chamber which lies 23 m beneath the seabed, some 600 m offshore. MTR fuel consists of small inclusions of enriched Uranium (U) within an Aluminium (Al) matrix and is similar to that used in other reactors. It is likely that radioactive swarf created during fuel milling activities associated with reprocessing is the initial source of these particles. DFR fuel consists of enriched U slugs in Niobium (Nb) cladding, the initial source in this case is considered to have occurred via dissolution procedures during reprocessing. The anticipated fission products are predicted around mass numbers of 95 and 140 amu [5] and include Yttrium (Y), Nb, Molybdenum (Mo), Xenon (Xe), Cs, Barium (Ba), Lanthanum (La), Neodymium (Nd), etc. EDXA and EPMA measurements of these particles confirm the presence of U, Al, Nd, Xe, Cs [3, 4] along with various elements such as Potassium (K), Calcium (C
Data Loading...
