Kansai Electric Power Co. said Wednesday it would suspend operations at two nuclear reactors after missing a deadline set by the industry regulator to build counterterrorism facilities.

Under stricter rules implemented after the 2011 Fukushima disaster, utilities are now required to build emergency off-site control rooms to serve as backup bases that can keep nuclear reactors cooled and prevent meltdowns in the event of a terrorist attack.

The suspension of reactors Nos. 3 and 4 at Kansai Electric’s Takahama plant in Fukui Prefecture — for about five months from August and four months from October, respectively — will be the second time for reactors to be shut down in Japan because such off-site facilities were not ready. The No. 3 reactor at the plant will be shut down from August 2 to Dec. 22, and No. 4 will be offline from Oct. 7 to Feb. 10, 2021.

The Nuclear Regulation Authority had told Kansai Electric it would have to suspend operations if the facilities — required to be at least 100 meters away from the reactors and constructed within a five-year period — were not ready around a week before the deadlines of August 3 and October 8 for the two units, respectively.

Utilities are expected to face hundreds of millions of dollars in extra fuel costs in 2020 for purchases of additional liquefied natural gas and coal. Nearly half of the country’s working nuclear reactors are expected to go offline for required security upgrades.

Osaka-based Kansai Electric declined to comment on what alternative power sources it plans to use to replace output from the two nuclear reactors. The company, which has said construction will now be completed by November, added that the move will result in its monthly fuel cost increasing by some ¥9 billion ($82.5 million).

The company will provide the required levels of power supply through procurement from other utilities, said Yoshinori Kondo, deputy head of nuclear business operations, at a news conference.

The company also said it plans to restart unit No. 4 at the plant on Thursday. The unit has been shut since Sept. 18, 2019, for scheduled maintenance.

Last April, the NRA said it would not allow power companies to operate reactors if they failed to put in place sufficient anti-terrorism measures by its deadlines.

Its requirements include an emergency control room, standby power supplies and reactor coolant pumps, to maintain cooling procedures via remote control and prevent the release of radioactive materials.

Kyushu Electric Power Co. said in October it would halt reactors Nos. 1 and 2 at its Sendai nuclear power station in Kagoshima Prefecture for over eight months from March and May, respectively. The shutdown is set to be the first under the stricter rules that were laid down in 2013 after the 2011 Fukushima nuclear crisis.