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« Beyond Nuclear calls out flaws in nuclear emergency plans during hurricanes | Main | Where is Irma headed? Are Florida reactors under threat? »
Thursday
Sep072017

Hurricane Irma bearing down on FL reactors, Hurricane Harvey water recedes from TX nuke 

Turkey Point Units 3 & 4, Homestead, FLThe Texas Gulf Coast cleanup from Hurricane Harvey has just begun and flood waters have receded from the South Texas Project (STP) nuclear power station near Bay City. While the Texas nuclear power plant dodged the bullet, now an extremely dangerous Hurricane Irma is barreling towards Florida. Four Florida Power & Light (FPL) reactors at two nuclear power stations (Turkey Point 3 & 4 and St. Lucie 1 & 2) on the Atlantic Coast are in the projected path of this Category 4 superstorm. Turkey Point 3 & 4, are located in Homestead, FL just south of Miami on the Biscayne Bay. St. Lucie 1 & 2 are on Hutchinson Island between the Atlantic Ocean to the east and Indian River to the west. FPL continues to track Irma's path and in anticipation of receiving hurricane force winds (presently 180 mph) announced that it will shut down the reactors in advance of Irma’s arrival to put the four atomic reactors in cold shutdown, their safest and most reliable condition. Turkey Pint is anticipated to have hurricane force winds by early Sunday morning. 

By contrast with the approach of Hurricane Harvey in Texas, STP nuclear power station made the decision to remain at full power throughout the storm. In fact, STP never experienced sustained hurricane wind levels above the 73 mph threshold that would have required shutdown. The reactors never lost offsite power from the grid that would have automatically shut down the units. However, significant flooding of the STP evacuatoin planning zone did occur including flooding of the reactor site. Bay City, TX, located 12-miles from the STP reactor site is one of the nuclear emergency host recepetion centers.  Matagorda County and Bay City officials had ordered two "mandatory evacuations" on August 24 and 25 disrupting the nuclear emergeny plan in anticipation of Colorado River flooding. The mandatory evacuation was lowered to "voluntary evacuation at your own risk" on August 29.  Bay City and Matagorda County personnel are vital participants in the STP radiological evacuation plan providing emergency workers, police, fire, medical support and evacuation bus drivers. Evacuations routes throughout the county became flooded and impassible. 

Both of the Florida reactor sites are designed for a “probable maximum hurricane” based on a hypothetical super cyclone recurring on a 100-year interval.  Turkey Point 3 & 4 nuclear power station’s plant grade is 18-feet above mean low water and co-located with the oil-fired Turkey Point Unit 1 and natural gas-fired Unit 2.  The reactor units are designed to withstand sustained winds of up to 145 mph and from a probable maximum storm surge of 18.3-feet and with external flood protection to 20-feet. Components vital to safety are protected up to 22-feet with the very important intake cooling water (ICW) pumps protected up to 22.5-feet above the mean low water level. Were these cooling water pumps to be flooded it would force the shutdown of the reactors’ cooling water intake system.

The St. Lucie nuclear power station is situated 19-feet above the mean low water level and designed toSt. Lucie Units 1 & 2, Hutchinson Island, FL withstand a maximum storm surge of 17.2-feet with sustained winds of up to 194 mph.

Nuclear power stations are robust facilities with redundant safety systems. This is because nuclear power is an inherently dangerous technology with potentially unforgiving consequences should a severe accident occur.

The story of a previous hurricane ordeal at Turkey Point reveals that a nuclear power plant is only as strong as its weakest link and how important a role luck may or may not play in protecting public safety and the environment.

On August 24, 1992, Hurricane Andrew made landfall in South Florida at the site of the Turkey Point nuclear power station. Andrew blew in as a Category 4 storm with sustained winds of 145 mph and gusts in excess of 160 mph. The decision had been made to shut down the reactors in advance. The hurricane knocked out all electrical power from the grid to reactor safety systems and the site’s emergency diesel generators successfully started up. The nuclear power station would be without offsite power for five days relying upon onsite emergency power to constantly cool the extremely hot reactor fuel protecting it from damage.

Each of the station's diesel generators consumed 100 gallons of fuel per hour, eventually requiring fuel oil shipments to be diverted from emergency facilities also without offsite power including hospitals. Andrew caused extensive destruction to on-site buildings and structures, damaging two 400-foot tall emission stacks for the two fossil fuel generating units. The cracked stack from the Unit 1 oil-fired electricity station threatened to fall on the nuclear power plants’ emergency diesel generator building which was vital in keeping the reactors from melting down during the five days without offsite power.

In addition, wind-driven missiles punctured one of the station’s 12,000 barrel fuel oil tanks just 30-feet from the tank bottom, spilling 110,000 gallons of combustible fuel oil that was then blown onto the nuclear site. As the fuel oil level in the tank fell due to the puncture, transfer pumps from large bulk oil storage tanks received a low-level alarm and automatically started transferring more combustible oil to the damaged tank that continued to flow out onto the reactor site. 

During the passing of the eye of the storm, station personnel managed to get to the power block and stop the oil flow.  However, Hurricane Andrew’s high winds had also blown over a high tower tank onto the nuclear power station’s fire suppression system rendering it inoperable. Given there was no operable fire protection system at Turkey Point, as only luck would have it, there was no ignition of the on-site oil spill. During the storm, the site telephone systems and radio towers were knocked and all offsite communication was lost for four hours and would not be reliable for 24 hours and all roads to the station were blocked by debris for days. 

The decision to shut down nuclear power stations in advance of extreme weather should not be made just on nuclear power plant conditions that a storm may or may not bring.  Operators, regulators and emergency authorities need to factor in the broader impacts to the radiological emergency planning zone that include the closure of evacuation routes and reception/medical facilities and the attrition of radiological emergency responders.