For high doses in a short time the risk is non-linear. But in Fukishima's case the dose is low and over a long period of time, and this is suspected to be linea

For high doses in a short time the risk is non-linear. But in Fukishima's case the dose is low and over a long period of time, and this is suspected to be linear. The competing theories are that lower doses of radiation have sub-linear risk, so if the linear model is wrong then people affected by the disaster are likely to be better off.