Nuclear Plant Near Epicenter Shuts Down

Your highly knowledgeable posts are very much appreciated.

Regards,

The power-grid by definition is a more reliable source of power than any single generator on a particular plant site. Your statement flies in the face of over 40 years of commercial nuclear power licensing and design. Any you are preaching to a degreed nuclear engineer from RPI who has worked in and around commercial nuclear power for more than 25 years -- since 1991 on risk assessment projects

Well, if you read the reports, it was the grid that failed first. Then one of the backup diesel generators. I spend a lot of time watching these kinds of safey analyses. Your "by definition" a priori assumptions are a postiori proven wrong. It isn't a small issue, actually. The reactor plant is designed to be many 9's more reliable than anything else. It is not hard to understand that it turns out to be so.

PS. A lot of folks suggest that had at least one of the Fukushima reactors continued operating, providing power for cooling they would not be where they are today. That does depend upon whether there was actual real safety significant damage to the system before the loss of cooling problems developed. It will be interesting to see where it comes out in the end.

The reactor plant is designed to be many 9's more reliable than anything else. It is not hard to understand that it turns out to be so.

The reactor plant is only part of the story at a commercial nuclear power plant. There are numerous single failure points in the combination of systems that convert the steam from the NSSS into MWe on the grid. Furthermore, the "9s" more reliable nature of the NSSS and its ECCS are designed to mitigate accidents and contain radiation. The reliability of individual important pieces of equipment range from one-in-one-hundred for equipment that is operated "manually" to one-in-ten-thousand for equipment that operates passively, e.g., a check-valve. Your "9s" statement is out of context to the issue of a reliable source of AC power.

As for Fukushima, the reason that one plant was not reconfigured to provide AC power to the rest of the units is because

(1) the load the other plants would provide is too small for the turbine/generator set -- commercial reactors are not sending steam to the turbine until they are at roughly 15% full power because of control issues with the feedwater regulating valves. Unit #6 is rated at 1100MWe -- 15% is 165Mwe. House load at a single shutdown NPP is at most 30Mwe mostly depending on the number of circ water pumps running; none at Fukushima.
(2) the transformers needed to convert 22kV from Unit #6 into 4160V on the safety buses of the four damaged plants are located outside of the turbine building -- swamped with sea water. Only a journalist would consider what you suggest to be actually practical.
(3) the grid failed first is inaccurate. The offsite power to the on-site safety buses switch gear at North Anna tripped open. The connection to the power grid was lost. At any utility run power plant, the relays are set to protect the expensive and lengthy time for either GE or Siemens to replace high-voltage equipment. The power grid was supplying AC power to the region during and after the earthquake on Tuesday, 23Aug11. Even at Fukushima, the problem was bring power grid AC to the plant switchyard rather than a wholesale power grid blackout. Loss-of-offsite power is one of the most anticipated events at a nuclear power plant; thus, the heavy emphasis on back-up alternative AC sources typically filled by marine diesel generators on-site.

There were 2 new drugs released by the FDA about eight years ago to treat radiation sickness, one for kids and one for adults. I am sure these are well stockpiled by now. I certainly hope those working in Japan’s disaster area have access to these if needed.

Radiation sickness can come about from many different radiation sources. The most common “radiation pill” known is potasium iodine, but it isn’t a cure all for radiation poisoning.

If a nuclear incident occurs, officials will have to find out which radioactive substances are present before recommending that people take KI. If radioactive iodine is not present, then taking KI will not protect people. If radioactive iodine is present, then taking KI will help protect a person’s thyroid gland from the radioactive iodine.

Taking KI will not protect people from other radioactive substances that may be present along with the radioactive iodine.

Here is the FDA’s fact sheet on KI: http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM080542.pdf

Some people can die taking KI, so you have to be careful with it. It isn’t some kind of magical shield against all forms of radioactive isotopes. Basically what happens when you take it is your thyroid absorbs the KI and then if radioactive iodine in ingested, the thyroid is “full” and wont absorb the radioactive stuff and the radioactive stuff passes through your body quicker.

Like I said before, I work in the nuclear industry and I haven’t heard of any new drugs, but that doesn’t necessarily mean that there aren’t some new stuff out there.

I wasn’t referring to KI but to pharmaceuticals released - and the first of their kind as far as I know. At the time I was working in a pharmacy weeknights and at the local hospital weekends.

How big are those generators? I have heard the press talk about them, both in this case and earlier in the year when one was surrounded by the flooded Mississippi river.

Sorry I took so long getting back to this subject.

I don't know exactly how big the Diesel-generators are at North Anna, but the plant where I worked is just a tad smaller than North Anna, and ours were a bit over 8000 horsepower. They were expected to carry 6.5 MW over an extended period of time. When we did startup testing, we ran them at 7.2 MW.

Each fuel tank is required to have a minimum of 100,000 gallons in them (one tank for each diesel). We usually maintained at least 110,000 to 120,000 gallons

The Diesels start automatically on a loss of offsite power or on a Safety Injection signal. They go from a standstill to full speed in less than 10 seconds. The lube oil and jacket water is maintained hot so there will be no problem in starting the engines.

The engines are started by compressed air, sequentially fed into the cylinders to get the engine rolling. Each engine has two starting air receiver tanks that each have enough air to start the engine 5 times, without re-pressurizing the tanks.

Want to know anything else?

The Seismic Monitoring System doesn’t have a connection to the Reactor Protection System. This means there’s no automatic shutdown directly due to the earthquake. However, if they lost offsite power, this means the grid was at least unstable. This would have tripped the turbine, which in turn would trip the reactor (2 out of 4 turbine governor valves shutting.)

Thanks for the info.