measuring the decay at earth’s core

This one is interesting – if only that it begins with an assumption, nuclear activity is at the heart of the sun and affects all the planets in various ways. At http://phys.org/print392615199.html … we learn that scientists are keen to find out how much fuel is left inside the earth – on the assumption it is the decay rate that provides the warmth to keep Plate Tectonics in motion (as well as several other earth phenomena). In other words, nuclear energy produced during natural radioactive decay. The paper is in Scientific Reports (Sept 9th 2016) and claims to predict (by modeling) how much fuel is left inside the earth. To do this they aim to count geo-neutrinos but this process requires a large detector (big money) situated a mile underground (in order to shield the research from cosmic rays).