Some neutrons will impact fuel nuclei and induce further fissions, releasing yet more neutrons. If these delayed neutrons are captured without producing fissions, they produce heat as well. Note that these equations are for fissions caused by slow-moving (thermal) neutrons. A steady rate of spontaneous fissions causes a proportionally steady level of neutron activity. U usually fissions on neutron absorption, but sometimes retains the neutron, becoming uranium-234. Quaternary fission, at 1 per 10 million fissions, is also known (see below). When absorbs a neutron, it either fissions or becomes . The reactor, a BWR-6 type, uses slightly enriched uranium which fissions generate energy as heat. The new droplets undergo desolvation and subsequently further Coulomb fissions. Such devices use radioactive decay or particle accelerators to trigger fissions. This criticality accident is estimated to have produced 4.4 x 10 fissions, or about . Tests soon indicated 180 fissions per gram per hour, which was unacceptably high. When the colony fissions, there are two ways new queens are decided. A typical power excursion is about 1 x 10 fissions.