6a) When two pieces of fissionable materials are brought close together: a) Their reactivity cancels out b) Their reactivity does not depend on how close they are. It depends only on their fission cross-sections c) They become less reactive d) They become more reactive
6b) Moderated Neutrons are sometimes called thermal neutrons. The word thermal is used to indicate that the neutrons are: a) High temperature neutrons b) Fast neutrons c) Are at the same temperature as their surroundings d) Very cold neutrons
6c) If a supercritical chain reaction starts in a metal assembly of fissionable materials, the first pulse of neutrons and gamma rays will last: a) A few minutes b) A few hundred seconds c) A few hundred milliseconds d) A few hundred microseconds
6d) For fissile materials, the overall variation of the fission cross-section with neutron energy in (eV): a) Is constant b) Slowly falls as the neutron energy gets lower c) Increases to thermal energies and then rapidly decreases at lower energies d) Increases as the neutron energy gets lower
6d) When two pieces of fissionable materials are brought close together: a) Their reactivity cancels out b) Their reactivity does not depend on how close they are. It depends only on their fission cross-sections c) They become less reactive d) They become more reactive
6e) Criticality accidents at Los Alamos Scientific Laboratory (Los Alamos, New Mexico / 30 Dec. 1958) and United Nuclear Corporation (Wood River Junction, Rhode Island/24 July 1964) both resulted in fatalities. The dose received by two victims were estimated to be: a) 10-50 Rems b) 100 to 500 Rems c) 500-1000 Rems d) Over 1000 Rems
