"cold shutdown" that doesn't require coolant circulation?

Hiddencamper

I really appreciate the first link. I've worked in 5s and 6s but dont have the same kind of experience with 3s and 4s. my knowledge of them is limited to reading their procedures, design documents, and SARs

rmattila

I've never been quite able to understand the difference between the "differences in BWR:s" document and the information about the Oyster Creek & Dai-ichi #1 found on the net: the document talks about one 29000 gallon IC tank and 90 min capacity, whereas Fuku 1 and Oyster Creek apparently have two IC tanks and several hours of capacity.

Hiddencamper

I think I'll be able to find out oyster's actual IC capacity.

That differences document states a 20 minute IC capacity (which is in line with Dresden's IC). I do know that IC capacity of the shell itself in some plants (like dresden) is only about 20-30 minutes per IC (i found this chapter of their FSAR online), but it can be extended to several hours with water pumped in via a diesel driven or electric driven motor from a water tank sitting outside the plant which refills the IC.

part of the reason for the smaller time is the greater decay heat load. Dresden is a very high power plant for the core size, so it has much more decay heat to deal with.

I've read claims that Fuku #1 has a 6 hour IC capacity in the heat exchanger shell....I'm a little skeptical (because I know some BWRs have much smaller ICs)...and there could be a translation issue here, but I have no verified evidence that they don't have a 6 hour IC capacity. I doubt we will ever get Fukushima's specifics for its IC size (in the form of a design document), but Oyster's should be in chapter 5 or 6 of their FSAR (they have a different FSAR layout so I'm not positive which chapter), and that's semi-publicly available. I know someone at oyster so I'll see if I can get a rough number.

rmattila

I have very limited knowledge of the GE BWRs. I know that the only ASEA BWR with IC, Oskarshamn 1, has 6 hour shell side capacity and capability to gravity-fill from the SFP (see http://www.ensreg.eu/sites/default/f...s%20111230.pdf , page 160), but that the capacity in SBO is limited to 2 hours due to the battery capacity needed to keep the valves open.

EDIT: The Spanish 466 MWe Santa Maria de Garona NPP, which AFAIK is close to FK1/1, apparently only has 1 hour worth of water on the shell side: http://www.ensreg.eu/sites/default/f...ress-Tests.pdf , p. 157.

Astronuc

This might also be of interest in understanding BWRs.

https://netfiles.uiuc.edu/mragheb/ww...20Reactors.pdf

Oyster Creek and Nine Mile Point 1 are BWR/2 units without jetpumps, but with direct cycle.


FYI - Passive Safety Systems and Natural Circulation in Water Cooled Nuclear Power Plants
IAEA TECDOC 1624 - http://www-pub.iaea.org/books/IAEABo...r-Power-Plants

Hiddencamper

Thanks to a colleague at Oyster, I've seen copies of Oyster's safety analysis report and their operations training manuals. The IC at Oyster can operate for 45 minutes each without a makeup water supply. so 2 ICs in service is 90 minutes. It also takes about 100k gallons to actually do a full cool down on the oyster creek reactor. This "several hours capacity" is not correct. The IC is only sized for a little over 90 minutes w/out makeup.

nikkkom

Interesting. Your position boils down to "we can't build an air-cooled heat exchanger which can withstand 9M earthquake, therefore let's not have it at all".

Wrong.

You are criticizing something different from my proposal, because in my proposal reactor water does NOT go directly thru air cooler; but anyway:
I am 100.00% sure Fukushima refugees would take a small, TMI-like transient radiation leak instead of a massive Cs-134/137 plume and ensuing permanent evacuation any day, thank you very much!

nikkkom

In a SBO, your primary concern is not to bring reactor to cold shutdown. In a SBO, your goal is to not let it melt down. If IC would be able to stabilize RPV at 120C for days without any power, I am a happy camper.

Hiddencamper

Ok so are you talking about SBO or are you talking about design basis accidents?

In either case, why are you going to install something that isn't capable of functioning in ALL environmental and accident conditions. You cant even accredit it as safety. There is absolutely no purpose in nuclear to install a piece of equipment with a safety function if it cannot handle the design basis earthquake, floods, weather events (wind snow tornado), plus any effects from design basis accidents including jet impingment/pipe whip due to High energy line breaks, LOCA, LOOP, etc. So yes, if you cannot build a structure that can withstand all of that, then it is not worth it to built it at all in nuclear.

As for not having to run reactor coolant through it, I'm curious... how are you going to transfer heat from one loop to another? So you are going to use reactor natural circulation combined with gravity for a primary loop heat removal...but how are you going to get the secondary loop to do the same. It is a large challenge, but not an insurmountable one, but I have a feeling (based off of experience) that adding in another loop to a natural air cooled heat exchanger for LWRs is not going to be effective without AC electrical power or some other motive force.

Hiddencamper

There is still operational leakage even during SBO, so makeup is an issue as well (albiet a long term one). If you cannot bring the system to cold shutdown, it is very difficult to makeup to the vessel using external pumps, and is an issue we saw at Fukushima, when they couldn't get RPV and PCS pressures low enough to allow injection.

The IC on its own extracts too much heat from the reactor, a detailed analysis would need to be performed, but its possible it would cool the system down so rapidly that if would lose natural circulation for a period of time. You need motive force to somehow turn the IC "on" and "off". Additionally you still need motive force plus a makeup source to have the IC maintain the vessel in a hot standby condition, although that force does not necessarily need to be AC power.

nikkkom

SBO must be a design basis accident. Otherwise we will have more Fukushimas.

nikkkom

They couldn't bring RPVs to atmospheric pressure because some idiot decided that prolonged SBO "can't happen" and therefore accident planning and personnel training regime does not need to include instructions and drills for venting RPVs in SBO conditions.

This corporate/regulatory blunder has nothing to do with technical merits of ICs.

If anything, if IC maintains RPV internals at near 100 C and pressure just a tad above 1 atm, that makes injection easier, not harder.

Hiddencamper

SBO cant be a design basis accident. Under plant design you can never have that many failures happen to put you in prolonged SBO. It wasn't a decision, its the fact thats how your design is of your facility. SBO is like any other extensive damage or severe accident, the fact that you got there in the first place meant that circumstances occurred which could not be prevented by design, and as such, you cannot plan for it like you would plan for any normal accident scenario.

Also, there are accident scenarios and procedures for venting the RPV, even in SBO conditions. The issues involved were due to the Japanese position to not vent until double the maximum containment design pressure. There were a lot of things that occurred as a result of this decision, such as not enough SRV accumulator pressure to actuate the SRVs in ADS or relief mode, failure of penetrations and seals in the PCV (and a potential breach in unit 2 PCV), etc.

rmattila

The term "design basis" is internationally a bit vague, since in some countries it refers to the original US definition, whereas in some countries additional more extensive conditions ("design extension conditions") and even severe accidents are in fact within the design basis. For example, the Finnish event classification is described in that post: http://www.physicsforums.com/showpos...&postcount=566 and a SBO falls under the DEC B category, where systems are only required to withstand external conditions with frequency once per 1000 years, not once per 100 000 years as the DBC4 systems.

rmattila

They're doing something like that at the Kudankulam VVER being built by Russia in India: http://www.frontlineonnet.com/fl2824...2282403300.htm

nikkkom

Glad that you are sure there are.

From where I sit, empirical evidence (Fuku) says that those procedures are not known to people operating NPPs, and when SBO occurred, they had no idea what to do.

Hiddencamper

Fukushima is a bad comparison to the rest of the world. Both plants I work at train on their SBO procedures, and it is well known how to handle the situation. If you read INPO's lessons learned, available here:http://www.nei.org/resourcesandstats...-power-station

you will see that it is very clear the Japanese deviated from several lessons learned by the US industry. And if you read the teleconference reports from the NRC website which were FOIAd from Fukushima, in the first one, it states very clearly that they were asking US plants (Exelon) to run simulator scenarios to figure out what was going on, and were asking GE for severe accident guidelines which are available at every US plant.

Japan really dropped the ball going into this, and the design of Daiichi didn't help it at all.

As for my comment about SBO, SBO is outside of design basis because it takes multiple accidents and failures, which is well beyond what you can realistically design for. To get to that point means something unpredictable happened, and as such, you need mitigation procedures, not blackout procedures.