Naval Neutrinos

Naval neutrinos, emitted by nuclear subs as a routine byproduct of the reactions producing propulsion, will have to be taken into account when studying neutrino oscillations, suggests a team of Stanford physicists.

Oscillation experiments probe the fascinating process by which one type of neutrino turns into other types. The power generated by nuclear submarines (100-200 operating at any one time) is only a few percent of all nuclear-generated thermal power in the world, and the neutrino flux from a typical naval reactor is only about 200,000 per sq. cm per second at a distance of 40 km.

This does not represent much of a background for the current generation of reactor-based neutrino-oscillation experiments. But for future reactor-based experiments, trying to perform higher precision measurements or those using a lower flux from a longer baseline (neutrino flux drops with the square of the distance), naval-reactor neutrinos will have to be factored in.

Stanford physicist Giorgio Gratta (650-725-6509, gratta@stanford.edu) says that, on the other hand, neutrinos from naval reactors may be used for a new breed of oscillation experiments in which the baseline for oscillations could be changed by simply "sailing the reactor" to a new position with respect to the (fixed) large detector. It is suggested that a nuclear ice-breaker could be chartered for this purpose. And, no, a sub's neutrino flux is not strong enough to give away its position. (Detwiler et al., Physical Review Letters, 4 November 2002.)