owner Toshiba to write down its investment in Westinghouse by "several billion" dollars. On February 14, 2017, Toshiba delayed filing financial results, and Toshiba chairman Shigenori Shiga, formerly chairman of Westinghouse, resigned. On March 24, 2017, Toshiba announced that Westinghouse Electric Company will file for Chapter 11 bankruptcy because of US$9 billion of losses from nuclear reactor construction projects, which may impact the future of the AP1000. Westinghouse emerged from bankruptcy in August 2018. Design specifications The AP1000 is a pressurized water reactor with two cooling loops, planned to produce a net power output of 1,117 MWe. It is an evolutionary improvement on the AP600, essentially a more powerful model with roughly the same footprint. A design objective was to be less expensive to build than other Generation III reactor designs, by both using existing technology, and needing less equipment than competing designs that have three or four cooling loops. The design decreases the number of components, including pipes, wires, and valves. Standardization and type-licensing should also help reduce the time and cost of construction. Because of its simplified design compared to a Westinghouse generation II PWR, the AP1000 has: 50% fewer safety-related valves 35% fewer pumps 80% less safety-related piping 85% less control cable 45% less seismic building volume The AP1000 design is considerably more compact in land usage than most existing PWRs, and uses under a fifth of the concrete and rebar reinforcing of older designs. Probabilistic risk assessment was used in the design of the plants. This enabled minimization of risks, and calculation of the overall safety of the plant. According to the NRC, the plants will be orders of magnitude safer than those in the last study, NUREG-1150. The AP1000 has a maximum core damage frequency of 5.09 × 10−7 per plant per year. Used fuel produced by the AP1000 can be stored indefinitely in water on the plant site. Aged used fuel may also be stored in above-ground dry cask storage, in the same manner as the currently operating fleet of US power reactors. Power reactors of this general type continue to produce heat from radioactive decay products even after the main reaction is shut down, so it is necessary to remove this heat to avoid meltdown of the reactor core. In the AP1000, Westinghouse's Passive Core Cooling System uses a tank of water situated above the reactor. When the passive cooling system is activated,