The Government is preparing to announce the construction of a new multi-billion pound nuclear fuel plant at Sellafield just weeks after an identical facility had to be closed because it was unfit for purpose.  Officials have advised ministers to reject a "third way" of dealing with Britain's civil plutonium stockpile - the biggest in the world - and forge ahead with a second mixed oxide (Mox) fuel plant at Sellafield costing up to ?6bn.  Independent scientists have suggested that instead of building an expensive new Mox plant to deal with the plutonium stockpile, Sellafield could use its existing plant to make inexpensive, low-grade Mox fuel that could be buried underground rather than being burned in nuclear reactors.  However, it is understood that ministers have been advised that this option is unviable, which leaves them a choice of either encasing the plutonium in ceramic blocks for burial as high-level waste, or gambling on yet another Mox plant costing ?3bn to build with lifetime costs nearer ?6bn.  The impending decision follows the report of the nuclear chief inspector, Mike Weightman, into lessons from the Fukushima disaster in Japan which will say that there is no need to cancel the decision to launch a major nuclear rebuild programme in Britain - despite the problem of waste plutonium still being unresolved.