Nuclear stopping channeling

The lack of nuclear collisions for channeled ions is not the only phenomenon that affects the pulse height. It is known that the electron density is much reduced along the channel. As a result, the electronic stopping power is lower and, consequently, so is the charge density produced by the heavy ion. Thus, not only the nuelear but also the recombination defect is reduced for the channeled ions. 

A very low power condition might appear trivial in a normal machine if the power decreases too much, it is made to rise again by the dedicated controls but in a nuclear reactor and especially in a RBMK, this is not so. Besides the reluctance of any reactor to increase power after a reduction, due to some isotopes which slow the chain reaction down and which are produced precisely in these transients, in an RBMK at low power the steam production in the channels stops and they fill up with water. As described earlier, the nuclear power level tends to decrease even more (the typical instabUity of RBMKs). 

The (d, ot) reactions are preferred over the (d, p) reactions because the later have low stopping power for incident deuterons and exit proton channels and are thus not suitable for depth profiling. Differential cross-sections for nuclear reactions i N(d, ps) N, i N(d,po)i5N, i4N(d, cco) 2C and i N(d,ai)i2c induced by deuterons from 0.5 to 2 MeV have been reported by Pellegrino et al. (2004). 

The worst accident which one could envisage happening to a fast reactor arises from the combination of two effects. The first is the small thermal capacity of the reactor core and the high rates of heat removal which are necessary. This means that if the coolant flow is interrupted the fuel may melt, even if the nuclear reaction is stopped, because of the heat generated by the fission prodncts which are formed during operation. The second effect is that if the fuel melts, then the channels through which the coolant flows may well become blocked. 

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