| 摘要 |
<p>Reactor fuel element for Na-filled fast breeders has a tubular sheath of Fe-based alloy resistant to liq. Na and filled with mainly metallic nuclear fuel. The fuel is heterogeneously distributed, pure U being in the centre, whilst the fission prod. Pu is conc. directly under the wall of the sheath and mixed with U and Fe, so that the fission prod. zone is fluid at the reactor operating temp. The tubular sheath/fission prod. melt/breeder centre zones are sepd. by diffusion-retarding layers of intermetallic cpds. (e.g. Fe2Ta between the sheath and melt and U2Zn17 between the melt and U centre). If the fission prod. overheats Na voids (spontaneous vapour formation) are avoided in the coolant at 889 degrees C. by the vaporisation of small amts. of Zn dissolved in the fission prod. and esp. by the decompsn. of the U2Zn17 at 947 degrees C. at the anticipated internal temp. of the rod. Max. utilisation of all heating surfaces is achieved, and excellent heat transfer occurs between the fluid melt and the sheath. Gases from fission can easily be released into the gas plenum.</p> |
