Exploring safety designs.

Jay put up a comment with a number of interesting ideas and questions. I’ll give my take on a few.

I’m curious if automatic scram of all reactors after a quake is the standard response plan everywhere.

It is and would have always been, even without Fukushima. Remember these safety plans are theoretical models. It doesn’t matter if components are rated “earthquake proof” if we can’t demonstrate the entire interrelated system is proof. And, short of an earthquake, we can’t.

No executive would entertain a scenario that might end with him in front of an inquiry board, with a “dumb as a styrofoam gas tank” Senator leaning forward and asking, “Son, at what point did yew realize that runnin’ a nuke-u-ler plant in an earthquake was a mistake?”

I imagine Japan is much the same. If there’s any flexibility, I’d guess it’s in the name. At what level are you allowed to switch from “earthquake” to “seismic activity”? That’s the Public Relations Threshold (which I just made up but am pretty sure is right).

…if the reactors were intact after the quake they could have left one running to provide power for a controlled shutdown of the others.

That would require permission to keep running a nuke during an earthquake, which was never going to happen. And running “jumper cables” from one to another seems an engineering and financial nightmare. These plants produce a billion watts of power. It doesn’t just get tossed on the grid, there’s a lot of electrical infrastructure. I don’t know how much of that you’d have to duplicate for the jumper cables, but I’m guessing somewhere between $$$$$$$ and $$$$$$$$$$$$.

Rather than that, they’d opt for another backup layer. Or, see below.

My guess is a reactor with intact containment is a heck of lot more tsunami resistant than diesel gens (and their fuel).

You are absolutely right. But again, “running a nuke during an earthquake” was never gonna fly in the p.r. world.

I’m so, so rusty on commercial nukes. But I think (correct me if I’m wrong, readers) aren’t some systems designed to run emergency vented steam across the turbine? That’s really elegant emergency engineering. You’re playing your problem against itself. You’ve lost electricity, so the core’s overheating. Thus you’re getting unwanted steam. Well then, shunt it to the turbine and now you have power for the coolant systems.

Maybe we should consider having older plants vulnerable to loss of power emergencies install a smaller modular reactor with passive cooling to run the bigger reactors.

That seems a bit kludge-like. And there will be no extensive and expensive retrofits of BWRs and PWRs. Most of these plants are deep into their planned lifetimes; some have gotten extensions. And now comes this.

Once these nuclear geezers are phased out we’ll either go nuke-free or go with “passively safe” designs as you mentioned. And your idea of siting the new ones at old nuke sites? I like it! It seems extremely promising to me.

To me the most terrible design feature was placing their electrical “backup/backup” (and possibly the “b/b/b”) where it (they) was vulnerable to the same thing as the “backup”

And thanks for the thoughful comments, Jay.

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About wormme

I've accepted that all of you are socially superior to me. But no pretending that any of you are rational.
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13 Responses to Exploring safety designs.

  1. Kenn L. says:

    Aerial video of the site from surprisingly close range:

    If they can fly this close, things must be improving.

    • wormme says:

      Well, “line of sight” to the exposed fuel is what doses you at those distances. Avoid that and you can avoid the really big doses.

      I’ve always thought that a double-rotored (to eliminate torque) small drone helicopter with cameras could be very useful in certain situations. This would be one.

  2. RF says:

    More good news radiation levels dropping
    http://www3.nhk.or.jp/daily/english/18_05.html

    • wormme says:

      That is good news. Assuming they can keep the water on.

      But if the measurements were made with massive steam clouds between them and the source? At that distance, the extra water in the air could have accounted for some or all of that 7% reduction.

  3. Sparkey says:

    Think about it, do you want to try and keep the grid running through an earthquake that’s tripping loads off left and right as poles are falling and faults galore are popping up everywhere? Even for moderate earthquakes it’s prudent to put all power production in a safe state and bring the grid back in a controlled manner.

    So by definition, the Japanese electrical grid was entirely disrupted, and none of the reactors could have restarted without permission anyway. I bet those guys were calmly going about their business getting the equipment ready to get back on the grid when suddenly a 23 foot wall of water appeared.

    And after the tsunami ripped the facility they couldn’t have gone critical even if they wanted.

    Remember, Fukushima had backup to the backup for the backup of the backup power in addition to batteries. The plants survived a 9 point effing 0 earthquake. They were ready for anything, except a 7 meter wall of water…

    So for any proposed backup sourced of power to be more reliable, it would have to be proof against a tsunami of any size. It’s not that the backups failed, it’s that their tsunami protection failed.

    • wormme says:

      That’s true. As sometimes happens, if something’s not a radiological concern I set consideration of it aside.

      Yes, that’s what gets me, the tsunami taking out everything. It wasn’t a record-breaking wave. Not looking to scapegoat anyone, I’d just like to see the rationale.

  4. DHP says:

    The hardest scenarios to deal with are ‘common cause’ failures like this. Having multiple redundant backups doesn’t do you much good if a single event can take out the whole chain.

    I haven’t seen many first hand accounts of what it was like at the plant. These are the closest I have found. It does sound like the quake itself did a fair amount damage even before the tsunami hit.

    I don’t know much about magnitude calculations — with an epicenter 140km away, how does that number translate into a local magnitude at the plant?

    http://www.ncregister.com/daily-news/japans-nightmare/

    http://www.yomiuri.co.jp/dy/national/T110316005275.htm

    “I was working near boilers on the 10th floor when the earthquake struck,” Kikuchi explained. “All the steam pipes around me broke loose, and the conditions were incredible. I could barely stand.”

    Soon after that, he observed the tsunami racing towards him. “That was beyond belief. We first saw a dark line on the horizon,” Kikuchi said, moving his hand in a wide stroke from right to left. “Then it came closer, and a white wave formed. When it got here, a huge overhang crashed into the building, some 10 to 15 yards high. Some 200 cars in the parking lot were all swept together.”

    Kikuchi was impressed by the reaction of the plant’s employees: “They knew the emergency manual, and we were able to evacuate quickly. There was no panic. But people were, of course, scared and surprised.”

    Strong horizontal jolts dislodged ceiling pipes and massive amounts of water started flooding out–this was the frightening scene experienced by a worker who was in the building housing the No. 1 reactor of the Fukushima No. 1 nuclear power plant when the earthquake hit Friday.

    His tale told to The Yomiuri Shimbun sheds light on the heavy initial damage the quake caused inside the building.

    The man works for a company contracted by Tokyo Electric Power Co. to handle inspections and maintenance of the reactor in Fukushima Prefecture. He had occasionally worked at the plant since last summer.

    When the earthquake struck, he was doing electrical work with some coworkers inside the containment building of the reactor, which was operating at the time, in an area where there was ordinarily no fear of radioactive contamination and thus no need for protective clothing.

    “It was such a powerful jolt I could hardly stand. I was thrown from side to side,” he said. “I thought, ‘That was no ordinary jolt.'” He also heard loud crashes of a crane, lighting and other equipment being bounced around, he said.

    Soon the lights inside the building went out and emergency lighting came on. An announcement came next, telling workers to stay where they were. But seams on metal pipes installed in the ceiling had been broken by the strong jolts and water started flooding out.

    Someone yelled: “This could be dangerous water. Let’s get out of here!” and they rushed down the stairs to the first floor exit.

    • wormme says:

      Exactly! I’d like to know what the Final Safety Analysis Report (or Japanese equivalent) selected as the largest tsunami the site could expect to see.

      Have been totally wrapped up in concepts and numbers here. Humanity has just been considered as a whole. So thanks for those two links. I’ll put them in a post.

    • Sparkey says:

      I don’t know much about magnitude calculations — with an epicenter 140km away, how does that number translate into a local magnitude at the plant?

      IIRC, the magnitude rolls off exponentially; however, given the magnitude (and remember the Richter is a log scale) at 9.0, a separation of only 87 miles (140 km) is not much attenuation at all.

      That’s my remembory from a seismology course I took back when a Walkman was hot.

      • wormme says:

        I’d wondered about how the intensity fades. The models we use in my field are point source, line source, and plane source. Tough, huh? Other Health Physics modelling is done by the PHP big brains, the Professional Health Physicists.

  5. Jay says:

    Wormme, thanks for answering my questions.

    As I suspected, the policy to scram on quake is influenced by politics and public perception. If we could just put nuclear safety above politics…ha, I’m dreaming.

    One observation I am making is that the net and blogs give a huge advantage in getting accurate information on a disaster only for people willing to seek out the information and pose questions to actual experts. Most people are still misinformed due to getting their info from TV news and talking heads. Still, us who want to know the facts are able to get them, unlike prior nuclear events where we had to rely on the vagaries of the government and plant owners.

    I would like to know if all nuclear plants use grid power for control, or if any tap into their own turbines for power. It would be ironic if plants generating hundreds of megawatts can’t even keep their lights on without the outside grid. I understand the plants are pumping out extremely high voltage which needs to go through a step down station and transformers to get to a useful voltage/current. So why not put a step down station near the plant?

    What still bothers me about automatic scram on disaster is that the unstated assumption is that either the backup power or the grid will always be available to protect the reactors. As I wrote, any event damaging enough to take out the backup generators will likely take out the grid for a significant time. They had a lot of backup eggs, but they were all in the same vulnerable basket!

    There has also been talk lately of the danger of EMP (either from solar flares, Iran or NKorea). The standard thinking is the grid would be down for a long time to replace the transformers and control systems. If the backup power at reactors were not hardened for EMP, there would be a very long loss of power incident and everyone would be wishing that they followed my advice and buried a small passively cooled reactor to power the big ones. I live 60 miles from calvert cliffs, which is the closest plant to DC.

  6. Mercy Vetsel says:

    I’m so, so rusty on commercial nukes. But I think (correct me if I’m wrong, readers) aren’t some systems designed to run emergency vented steam across the turbine? That’s really elegant emergency engineering. You’re playing your problem against itself. You’ve lost electricity, so the core’s overheating. Thus you’re getting unwanted steam. Well then, shunt it to the turbine and now you have power for the coolant systems.

    Hey, isn’t this the type of backup they were trying to test at Chernobyl when things went somewhat off track? I know that Chernobyl was graphite, but I seem to remember that they were experimenting with some approach for generating power during an emergency and thus the irony of the disaster being caused by safety testing.

    -Mercy

    • wormme says:

      Just Wiki’ed it. Not quite the same. Their setup showed a potential one minute loss of power between the generator going off and the other systems kicking in. They deemed that too long, and tried to harness the “spin down” of the turbine for up to 45 more seconds of (dwindling) power.

      Assuming we have emergency steam shunting (again, I’m not sure) if it wasn’t in the initial design, we can be sure they didn’t do it with the reactor running.

      And yes, it was an epic of irony.

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