I was rather disappointed by the sensational title and superficial contents of the article on the Prism reactor (PE August 2012).
It is common knowledge that fast reactors are capable of 'burning up' transuranics but the problem lies in scaling them up safely. I would have hoped a serious engineering magazine like PE could have dealt with the measures proposed to overcome this problem in the case of Prism.
As an inherently safe design, Prism needs to be capable of shutting itself down and getting rid of its decay heat without the sodium getting near its boiling temperature (a little over 800ºC). This does not present a problem in a small reactor like EBR II but large fast reactor cores tend to have positive void coefficients, resulting in a runaway power excursion if the sodium boils. Measures such as the use of an annular core to avoid this, tend to degrade the neutron spectrum, making the reactor less effective as a transuranics burner.
Hopefully a future article will give us details of the means relied on in Prism to avoid this difficulty.
Sam Hosegood, Dorset