Void coefficient reactor is reduced. In boiling-water reactors with large negative void coefficients, a sudden pressure rise (caused, for example, by unplanned closure of a steamline valve) will result in a sudden decrease in void content: the increased pressure will cause some of the steam bubbles to condense ("collapse"); and the thermal output will possibly increase until it is terminated by safety systems, by increased void formation due to the higher power, or, possibly, by system or component failures that relieve pressure, causing void content to increase and power to decrease. Boiling water reactors are all designed (and required) to handle this
2007 Guatemala City sinkhole on the city's aging sewerage system, and have speculated that more piping failures are likely to develop unless action is taken. Several rainstorms also contributed to the sinkhole's collapse, as stormwater percolated into the ground, further dissolving the rocks beneath Guatemala City. Citizens of Guatemala City near the sinkhole also reported hearing rumblings a few weeks before its collapse. The INSIVUMEH (Guatemala's seismology institute) had placed a seismic meter there before the disaster; a robotic camera system was supposed to enter the cavity, but the disaster occurred first. On February 23, 2007, the sinkhole collapsed, forming a very large, deep