Nuclear Energy Activist Toolkit #36
The Reactor Core Isolation Cooling system is relied upon at most boiling water reactors (BWRs) to provide makeup water to the reactor vessel housing the nuclear core to compensate for water being boiled away when the normal makeup system is unavailable. Abbreviated as RCIC and pronounced like “rick see,” this system likely used up its 15 minutes of fame during the Fukushima accident.
RCIC features a steam-driven turbine. Steam produced by the decay heat from the shut down nuclear core flows through the RCIC turbine. Steam exits the RCIC turbine and flows into the suppression pool where it gets cooled down and converted back into water. The steam supply and exhaust piping appear in red in the upper right portion of the graphic.
The turbine’s shaft is connected to a pump. This pump transfer water from either the condensate storage tank (a large metal tank located outside the reactor building) or the suppression pool (a large body of water in the basement of the containment building) into the reactor vessel. The pump’s suction and discharge piping appear in blue on the left side of the graphic.
The RCIC system’s valves and turbine controls are powered from batteries rather than from alternating current (ac) sources. Because steam comes from the decay heat of the nuclear core and power comes from batteries, the RCIC system is the only permanently installed system at most boiling water reactors that is capable of providing makeup water when both the normal power source (the electrical grid) and the backup power source (the emergency diesel generators) are unavailable.
Earlier this year, the NRC placed a video file in its online electronic library showing operators using the RCIC system at the control room simulator for the Duane Arnold nuclear plant in Iowa. [Caution: This electronic file is over 173 megabytes in size and can take a moment or two to download and open.] The operators demonstrated how they could manually control the speed of the RCIC turbine, and hence the rate of makeup flow provided by the RCIC pump.
Normally, the RCIC system is automatically controlled. The operators adjust the desired makeup flow rate (e.g., 400 gallons per minute) on a controller. This controller then opens or closes the turbine control valve (shown just above the turbine on the right of the graphic) as necessary to maintain the desired flow rate.
If the automatic controller is broken or when the batteries are exhausted to the point they no longer permit the automatic controller to function properly, the operators can manipulate the trip/throttle valve (circled in green on the graphic) to regulate the amount of steam flow to the RCIC turbine and the rate of makeup flow to the reactor vessel. The video shows how operators would take the steps necessary to manually operate the RCIC system.
As suggested by its being in NRC’s ADAMS rather than on Netflix, this video won’t appeal to mass audiences. But it might interest a niche audience.
Senior reactor operator Tom Gordon spends the first half of the video explaining the RCIC system and showing the applicable handswitches, indicating lights, and gauges on the control panel. Reactor operators then demonstrate the steps necessary to manually control the RCIC turbine speed during the second half of the video. [Hint: Moving the cursor near the lower edge of the video screen reveals a timeline that can be used to skip ahead or return back to portions of the video.]
The video also shows the annunciator panels (the flashing lights at the top of the control panels and the source of the periodic audible alarms).
The operators are using good three-way communications: (1) the initiator gives an instruction or asks a question, (2) the receiver parrots back the message, and (3) the initiator confirms the proper message was heard. The nuclear industry adopted this method to reduce miscommunications.
This snapshot from the video shows the control rod display at the upper left and the reactor vessel and primary containment mimic at the upper right. Displays such as these provide the operators with instant status of key parameters. For example, the green and red lights within the reactor vessel and primary containment mimic indicate the open (red) or closed (green) position of all valves on pipes that penetrate through the containment’s concrete walls.
This video was developed by Duane Arnold’s owner and placed in NRC’s ADAMS as part of enforcement action taken by the agency upon discovering that the RCIC system had not been properly maintained. The NRC also issued a White finding (the third most serious of the agency’s green, white, yellow and red sanction levels) for the violation.
Take a look see at RCIC.
The UCS Nuclear Energy Activist Toolkit (NEAT) is a series of post intended to help citizens understand nuclear technology and the Nuclear Regulatory Commission’s processes for overseeing nuclear plant safety.