Large Break Loss of Coolant Accident

A SIMULATED large break loss of coolant accident at a Pressurized water reactor.

To give you an idea what is going on, at the start of the accident, the camera is facing towards the center reactor controls area of the control boards. This is where the operators can position control rods in the core. We typically run with all rods pulled fully out, and control reactor power with steam demand (main turbine load) and boron concentration in the reactor coolant.

When the accident starts, you can see that white arrow just right of center flash, which indicates that all the control rods fell into the core. The large black rectangular board behind and above the arrow is position indication for each individual control rod. I doubt you can see it, but there are red LEDs that would show the rods traveling in.

Starting at 0:49, as the camera begins to pan back to the right, what you are looking at is our emergency systems control boards. What is happening is that these safety injection systems and containment isolation systems are automatically responding to the accident. The safety injection systems are lining up to inject high pressure borated water into the reactor vessel, followed by low pressure safety injection. The reactor containment building is automatically isolating itself from the environment to contain any damage within the structure.

As the camera continues to pan right, you are basically just seeing all these various systems performing their automatic safety function.

At 0:59, you are looking at the "secondary" plant control board. This is where we control things like the steam generators, main turbine, condensate, cooling towers, feed water, etc. This is all non-radioactive systems that are used to support the main turbine which turns the main generator to produce power. What you are seeing occur in this video is the main turbine and feedwater systems tripping off and isolating.

At 1:02, you are looking at the electric plant control boards. Here, we control the main generator which ties to the electric grid and our emergency diesel generators. What is happening here is the main generator is tripping offline and the emergency diesel generators are starting up. They will not load onto the bus unless we lose offsite power. So, our loads are automatically transferred to offsite power when the main generator trips offline. This is what will power all of our emergency pumps. If offsite power fails, then our emergency generators will automatically power the bus and the pumps.

So that is a simplistic overview of what happens when the worst case loss of coolant accident occurs on a pressurized water reactor. If everything works correctly, the operator only needs to walk down his panels and monitor. We are there in case things go wrong, and we go through an 18-20 month training program to ensure that we can combat any failure that may come up.

Feel free to post any questions you have in the comments.

Category:

Education

Tags:

• nuclear
• reactor
• energy
• power
• coolant
• scram
• trip
• simulator
• accident
• PWR
• BWR

[fyadcorp]

take out that stupid music

[JustinHEMI05]

@fyadcorp No.

[JustinHEMI05]

@wolfcatsden Yep is sure was. Had they left well enough alone, the plant would have taken care of itself. They didn't understand or believe what their indications were telling them, and they acted contrary to what they should have done. Of course, operators are trained much differently today, thanks in large part to TMI.

[tavisho]

@JustinHEMI05 ok......im aplying to I&C supervisor or maybe i could go all the way and become and RO operator.......so.....maybe well be in contact. Bye 4 now

[JustinHEMI05]

@tavisho Peach Bottom Atomic Power Station. Dual unit GE BWR-4/MK-I containment. I am currently licensing on a westinghouse 3 loop PWR (the one in this video).

[tavisho]

@JustinHEMI05 ours is a ge bwr-5 ( well it is really 2 units and the only 2 reactors in méxico) and yours?

[JustinHEMI05]

@tavisho Excellent!!!

[tavisho]

@JustinHEMI05 i just finished my third regulatory course by the fsar and it is called "tecnología laguna Verde"

[JustinHEMI05]

@tavisho I have a senior reactor operator's license on a BWR, so I'm quite familiar with the failure mechanisms. That said, a PWR is different, of course, but depending on the manufacturer, they all have between 2-4 cooling loops which are similar to the recirc loops of a BWR. The DBA LOCA for my particular PWR is a double ended shear of cool leg piping.

[tavisho]

do the pwr have recirculation pumps if they dont..........where do they present the LOCA? cos in the bwr the loca is most likely to take place in the recirculation loops

[JustinHEMI05]

@Froginthemouth406 Oh no problem. :)