Areactor has been operating for a long time at a power of 2660 mwt. the operator decides to shutdown the reactor. a step reactivity of ~ 10 \beta is introduced by insertion of the control rods. the time (in seconds) for the power to reach 0.1% of the steady state value is most nearly (solve; no choices giving): :

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.