2011 Japanese Earthquake and Tsunami - News and Analysis

[chaanakya]

Channakya,

I think you are talking about an Ammonia turbine. They are most efficient when they have access to a really cold heat sink. They are popular in the Arctic circle areas and near ski resorts in the Lower 48, esp. when they can tap into low grade geothermal springs, in the 80C-100C range. They extremely reliable and low maintenance though should be handled with caution as liquid ammonia can be toxic and dangerous.

Cold heat sink, -20C or so is essential for efficiency. I don't think it gets that cold in Fukushima and certainly does not in most of India.

Ammonia is one fluid, but obviously not suitable for Indian or even Fukushima Situation as you pointed out.. But you are not far off the mark. Rankine Cycle may ring a bell. You would be knowing better about these turbines. Check NAL.

Also we are not talking of multi MW type power output.

I would say it is working and has worked in few places. Though not all details are public, technology is fairly well known. Might not be very cost efficient. if NPPs have not gone for it , there must be some other issue.

Anyway , that is OT here and was in response to Lalmohan.

[Amber G.]

so, if i understand correctly, the heat in the spent rod pool is exponentially decaying and apart from some short term heat exchange, is not of much use? however, the heat from the main cooling circuits, post turbine work, i assume can still be used via heat exchanger for district heating type applications?

Few points:

1. The battery backup at Fukushima NPP, (from what I have been told by people who ought to know) was primary for managing valves in the cooling system, significant amount of energy (till the diesel generators kicked in) was from the steam (from decay heat etc). Power requirement for cooling is not a trivial matter (see Ramana's post.. or size of those diesel generators.).

2. The above is because the pumps in the cooling systems run on AC current, which generators produce directly but it still an engineering challenge to get it from batteries (in that high power rate - remember these are decades old designs)

3. The things failed (details still to be investigated) and the pumping system/cooling system did not work (even when power was restored).

4. In Chernobyl the main cause of all that going wrong was, ironically, a silly test to test how that kind of cooling system will work (roughly speaking)

5. The decay heat is neither exponential or steady-state, it is quite complicated.. not only depends on type of fuel, reactor type but mainly how long the reactor was running before shutdown.

A approximate formula people use is something like k((T-T')^-(0.2) -T^(-.2)) where T' is the time the reactor was running before shutdown. (k = something like 0.07 for Fukushima) (Formula is approximate)

MITNSE site had a nice graph for Fukushima decay heat (Their values and formula is little different than mine given above)

I have given values per ton in some of my previous posts after 1 yr and 10 Yr.

With regard to I-131 and other radioactive stuff spewed in air:

1. The values are out in open source or one can ask and get the number (No one is hiding it, I don't think any one can hide it)
2. Even values obtained in Ohio (see my previous post) one can estimate and will get order of magnitude correct. One need not insinuate that people like me, scientists, and Tepco officials all are lying.
3. Values are indeed very high (specially Xe which turns into I-129), I-131 etc which spewed out
Not so bad news about above is:
- Unlike Chernobyl (land locked) lot of it went over ocean.
- Radiation is very closely monitored. Evacuation, and no eating of I-131 laced food etc...People are listening to scientists vs MCQ's
- The number of deaths due to radiation etc are still nil ( Remember, we have a major earth-quake / tsunami which has killed thousands)
- Scare mongers are being exposed and are not having too much effect on Japan's people. ( Not counting dork media, MCQ's here, and protests in India like this )

Hth.

[Amber G.]

Also we are not talking of multi MW type power output.

Okay, how much power are we taking here? Care to give a number? (You may like to see Ramana's post long time ago)

[Sanku]

http://www.ynetnews.com/articles/0,7340 ... 57,00.html

Japan's decision to wait until now to raise the ranking of its nuclear disaster to the most severe level on the global scale does not mean that Tokyo authorities have been downplaying the disaster, the International Atomic Energy Agency said Tuesday. (AP)

IAEA trying hard to clean up the egg on their face. But I cant understand why they are so touchy? Who takes them seriously anyway? Does anyone?

[Amber G.]

Lalmohan, GP:

[Amber G.]

Today the Japanese Nuclear and Industrial Safety Agency revised its INES rating of the Fukushima Daiichi event. The previous assessment treated the events at each of the ailing reactors as separate: the core damage to units 1-3 resulted in an assignment of a 5 (accident with wider consequences) for each reactor; the problems at unit 4′s spent fuel pool were assigned a 3 (serious incident). NISA is now treating the situation as a single event, assigned a rating of 7 (major accident). This rating is still being assessed as information about the disposition of radioactive materials originating at the reactor site comes in.

Because the rating is now the same as that assigned to the Chernobyl accident, the blog has received a number of questions about how the events at Fukushima differ from it. We present a sequence of events at Chernobyl, along with links to some denser technical matter for interested readers, and an IAEA report on the human costs of the disaster. For comparison, it’s been estimated that the radiation released by the Fukushima reactors is 1/10th that released to the environment at Chernobyl.

Chernobyl

On April 26th 1986, the most serious nuclear accident in history took place at Unit 4 of the Chernobyl power plant located 130 km north of Kiev, Ukraine. The site had four RBMK-1000 reactors. These reactors are graphite moderated boiling water reactors and did not have a containment structure. Reactor containment is the large and thick concrete and metal structure surrounding the nuclear reactor. Its purpose is to protect the reactor from external damage, and to contain radioactivity in case of a significant reactor failure. By regulation, all western BWR and PWR reactors have to have a containment. Additionally, the RBMK design also had a very large and positive coolant void reactivity coefficient, meaning that as the coolant (i.e. water) temperature increases, the reactor power increases. This positive coefficient is not present in BWRs or PWRs.

A brief summary of the events is presented here, a detailed description can be found at http://www.world-nuclear.org/info/chernobyl/inf07.html. The following document (http://www.iaea.org/Publications/Bookle ... rnobyl.pdf) also includes information about the health and environmental effects of Chernobyl accident.

On April 25th, unit 4 was to shut down for routine maintenance, prior to which a safety test was to be performed. The test was to evaluate how long the turbine would spin and supply power to the main water pumps in the event of a loss of electrical power. This test had been tried in the past and new adjustments were made to allow the pumps to be powered longer.

After a few delays due to demand for electricity from the grid, the test was performed by an inexperienced crew. The test was to be performed at ~30% of full power. A series of operator actions, including the disabling of automatic shutdown mechanisms, positioned the reactor in a very unstable condition, in which the reactor was at very low power. As operators withdrew control rods in an attempt to increase the power to the level necessary for the test, the reactor heated up. The reactor’s positive void reactivity coefficient resulted in a rapid increase in power. Control rods were inserted in order to staunch this increase in power. The unusual design of these control rods, which had graphite “followers” (recall that graphite is a moderator) worsened the situation by increasing power at an even more rapid rate. The result was a power excursion of between 100 and 500 times full power as the rods were inserted into the reactor.

This large power surge caused the fuel to disintegrate. As the fragmented fuel interacted with the steam/water mixture, a steam explosion occurred. This blew off the reactor’s massive vessel top (1000 tons) which penetrated the reactor building concrete, and dispersed burning graphite and fuel. This initial explosion and the subsequent fire sent a plume of radioactive gas and particulates into the environment. Further explosions were caused by production of hydrogen in clad/steam chemical reaction.

The radiological consequences of the Chernobyl incident were severe. The radioactive plume that emanated from the reactor contained not only volatile radioactive nuclides (such as Iodine-131, Cesium-137) which have been observed around Fukushima, but also many non-volatile ones, which were in the disintegrated fuel pieces. This plume got carried far away by wind and deposited radioactive particulates over many places in the northern hemisphere. 31 of the plant operators and firefighters got lethal radiation doses. The risk of cancer to surviving staff members and to residents of the 30 km evacuation zone is predicted to have approximately doubled as a result of exposure. An important thing to note about the Chernobyl accident is that the evacuation was not started until a nuclear reactor in Sweden (1000 km away) detected elevated radiation levels.

About 97% of the radioactive nuclides found in spent or partially spent fuel remain inside the fuel rods, as long as they do not melt. Of those, a fraction are noble gases (such as Xe-135), and many are solid materials. When the fuel melts, the noble gases escape the fuel and leak to the environment; however, due to being noble gases they do not react chemically, and disperse in the atmosphere. Iodine-131 (deposits in thyroid), Cesium-137 (30-year half-life) and Strontium-90 (replaces calcium in bones) are the three most significant non-gaseous fission products. Due to the explosion of the reactor vessel in the Chernobyl accident, these products were released as well, thus significantly contributing to the dose to the public.

Chernobyl unit 4 is now enclosed in a large concrete shelter which was erected quickly (by October 1986) to allow continuing operation of the other reactors at the plant. The last reactor, unit 3, was shut down in 2000. A New Safe Confinement structure is due to be completed in 2014. It is being built adjacent to the facility and then will be moved into place on rails.

Source:http://mitnse.com/2011/04/12/new-provisional ... yl-primer/

[Sanku]

http://www.nytimes.com/2011/04/13/busin ... tml?src=mv

Wall Street Slides as Nuclear Crisis in Japan Worsens

Its starting.

[Amber G.]

IAEA trying hard to clean up the egg on their face. But I cant understand why they are so touchy? Who takes them seriously anyway? Does anyone?

If any one is getting touchy, I don't think it is IAEA, and I am sure that it is not IAEA which needs to clean an egg .. but for the Serious question, (Who takes then seriously) serious answer:
These don't: (They say IAEA is evil, not to be trusted, etc..)



Source of above: http://www.telegraphindia.com/1110412/j ... 843538.jsp

But people like me.. And I believe virtually all in brf (except perhaps 1.5 people who don't - correct me if I am wrong) do take IAEA seriously.

[Lalmohan]

wall street is sliding due to poor results from industrial groups and big banks in the US out today and continuing worries in mid east, and yes japan is a factor, but not the only one

[Sanku]

For posters who may be reading this the example has posted two picture and alleged that they have certain views of IAEA, however without providing any information to support it what so ever. The quoted article does not even mention IAEA or report any link between IAEA and Jaitapur opposition.

So two pieces have been fabricated by insinuation
1) Belief or disbelief of some individuals about IAEA.
2) Link between Jaitapur and IAEA.

I strongly condemn this unscientific and completely amoral habit of associating with people PoVs dreamt up on their behalf.

I am reporting my own post to moderators as open protest about continuing posts which repeatedly attempt character assassination of people (whether on BRF or outside) by falsified allegation on people fighting for their very life.

From the above link.

Raut said he has at least three cases foisted on him — one barring him from entering his own village — for being part of protests against the project. But the middle-aged man is not deterred, the latest inspiration coming from Anna Hazare, a fellow Maharashtrian. “This village had produced 14 freedom fighters and now Anna Hazare has shown us the way. We will protest till the project is removed from our village.”

It is horrendous to mock and attack people such as above. We may or may not agree with them, but this behavior is not condonable.

[Theo_Fidel]

1. The battery backup at Fukushima NPP, (from what I have been told by people who ought to know) was primary for managing valves in the cooling system, significant amount of energy (till the diesel generators kicked in) was from the steam (from decay heat etc). Power requirement for cooling is not a trivial matter (see Ramana's post.. or size of those diesel generators.).

2. The above is because the pumps in the cooling systems run on AC current, which generators produce directly but it still an engineering challenge to get it from batteries (in that high power rate - remember these are decades old designs)

It remains to be seen if this is exactly true. My understanding is that Batteries were lost as well in the Tsunami which forced the plant into a monitoring only stage and being unable to operate valves and pumps. If it is true that the batteries did not operate the cooling system then that is a terrible design flaw. It left the entire plant vulnerable to a single point failure, the generators.

The Palo Verde Nuclear plant was upgraded in 1995 to operate for 3 days on industrial strength old technology flooded lead calcium batteries. This is a 4000 MW plant. It is relatively trivial to get 7 days worth of bachup battery power into a power plant. Big warehouse yes, hydrogen venting system yes, but relatively minor costs, say $20 Million or so.

[ramana]

Western media had this snigger while talking about Chernobyl(Incident level 5) impling that their technology was superior. Now after Fuikushima which is a much bigger (incident level 7) per IAEA this smirk will be wiped off hopefully.

[Amber G.]

Western media had this snigger while talking about Chernobyl(Incident level 5) impling that their technology was superior. Now after Fuikushima which is a much bigger (incident level 7) per IAEA this smirk will be wiped off hopefully.

^^ Am I misunderstanding some thing, or is it a typo, Chernobyl was level 7 and not 5.

[ramana]

WoW! I thought it was a 5 my mistake. So now its equal equal.

[Mort Walker]

1. The battery backup at Fukushima NPP, (from what I have been told by people who ought to know) was primary for managing valves in the cooling system, significant amount of energy (till the diesel generators kicked in) was from the steam (from decay heat etc). Power requirement for cooling is not a trivial matter (see Ramana's post.. or size of those diesel generators.).

2. The above is because the pumps in the cooling systems run on AC current, which generators produce directly but it still an engineering challenge to get it from batteries (in that high power rate - remember these are decades old designs)

It remains to be seen if this is exactly true. My understanding is that Batteries were lost as well in the Tsunami which forced the plant into a monitoring only stage and being unable to operate valves and pumps. If it is true that the batteries did not operate the cooling system then that is a terrible design flaw. It left the entire plant vulnerable to a single point failure, the generators.

The Palo Verde Nuclear plant was upgraded in 1995 to operate for 3 days on industrial strength old technology flooded lead calcium batteries. This is a 4000 MW plant. It is relatively trivial to get 7 days worth of bachup battery power into a power plant. Big warehouse yes, hydrogen venting system yes, but relatively minor costs, say $20 Million or so.

Can you show me a battery back up system for a 3-phase 1000-4000 KVA UPS system that would last 7 days? I would certainly be interested. The cooling system pumps and valves, and their motor systems, are all 3-phase for industrial systems. The cost and environmental hazard for this many batteries is tremendous and that is why you use an engine generator system, which unfortunately got wrecked in the tsunami.

[Mort Walker]

It appears there are now trace amounts of strontium being found. Lets see if the reports are confirmed.
Slight Amounts of Strontium Found

[Amber G.]

I would be curious to see if the "report button" works for others who report..

t is horrendous to mock and attack people such as above. We may or may not agree with them, but this behavior is not condonable.

Agree 400%. but for those who use colorful terms like ""almost virgin" to describe meltdowns, and routinely use quotes like:

Madarassa math is your specialty; ignorance coupled with blatant foul mouthed hate to India and Indians which you proudly wear on your sleeve.

Are getting upset with my opinions..
Never-mind the link where the pictures came form was given so as not to mislead..
Here it is again:http://www.telegraphindia.com/1110412/j ... 843538.jsp
And a quote:

The speech was peppered with references to Japan’s nuclear crisis, hardly surprising in an area where Fukushima, the stricken nuclear reactor, is a buzzword. “We saw what happened in Japan.

[/quote]

Besides, if one really think that these guys are pro-IAEA, why not just say so.. and just say they differ with my opinion.
No one was mocking anyone.. pictures with the source link are neither haram.. nor OT in this connection.,

[Bade]

All the data you need for monitored US regions are here too.
http://www.epa.gov/japan2011/

[Amber G.]

WoW! I thought it was a 5 my mistake. So now its equal equal.

Before Fukushima, there was only one level 7, and one level 6.. TMI and all others were L5.

[Theo_Fidel]

Mort there are 120 hour batteries but in this case you would have to use separate strings, set to kick in sequentially. Typical battery string would only last 8 hours. I've seen a data center with 12 separate strings.

I don't think there is such an off the shelf system. The systems I'm taking about are engineered and customized which is how I run across them. Many of the components are supplied by Swift power per my spec. catalog. They also have a in-house team who are very good at what they do. Apparently highly recommended per people here. I see their 10,000 amp 48v modular 3-phase rectifiers. A couple of those should cover our need, no.

http://www.swiftpower.com/integrated/pr ... oducts.htm



You are right that it would be expensive. But compared to the other backup systems it is a trivial amount. A single small 1000KVA generator and associated systems can cost $1 million+ depending on supplier.

[Amber G.]

^^^ Theo, you may like to reread Ramana's post in way back in March ... (who worked with few types of NPP )
viz:

A nuke power plant has a Diesel Generator bldg. The Diesels are size of ship engines and hooked to generators. Usually two sets as back-up. They provide power to pump water coolant to shut the plant down. ..... Most likely based on TV pictures the DG bldg got flooded or swept away. Battery back up is no sufficient...While the coolant is pumped to reduce heat the control rods are scrammed down. These are also water powered with inlet and withdraw lines. ....The fail safe is inlet water pushes the control rods to shut the reactor down. However the reactor vessel is still hot and needs to cool down. That is where the coolant .....
Oh BTW, the D-G at a nuke plant generate MWs of power and don't think any emergency power sets.[will do] ..

For perspective, even after a shutdown, (see the graph I posted a few posts above) core is still giving heat of the order of 50-100 MW.. and 10-20 MW even after a few days. You need powerful pumps to sink that much heat.

You may like to check out, eg: http://www.nucleartourist.com/systems/diesel1.htm

[saip]

WoW! I thought it was a 5 my mistake. So now its equal equal.

Before Fukushima, there was only one level 7, and one level 6.. TMI and all others were L5.

But Chernobyl was an act of man -- a very negligent man --and Fukashima is an act of God -- perhaps a very vengeful God!

[Mort Walker]

Theo,

Remember batteries are used through the UPS system that powers 3-phase motor equipment. 3-phase AC power is sent through the UPS and when it detects main power loss, it switches to batteries in milli-seconds. A data center needs DC power, or at least DC-AC-DC, so the problem is different. AC motors, especially for pumps & valves, have an in-rush of current when first started, then settle down. They are also subject to phase changes or a loss of a phase and then don't work right. As AmberG said, you need powerful pumps to sink that much heat, and without it at Fukushima the batteries back up through the UPS system provided 8 hours. Consider that these pumps probably require 208V 3-phase motors that need a lot of continuous current.

The link you provided at the bottom shows which UPS systems they have. I can assure you, Mitsubishi, Toshiba, Eaton-Power Ware and some Indian companies make excellent high capacity, > 1000 KVA, 3-phase UPS systems. The batteries on these 3-phase UPS system need maintenance and replacement on a regular basis.

[harbans]

Going through a few posts above, logically it's unlikely that backup Battery systems would have power to circulate the coolant and completely substitute all process functions in a nuclear plant. More likely they would be in use for control panel lighting, Emergency lighting in reactor buildings, emergency communication facilities, emergency coolant injection pumps, emergency critical valve operations. Possibly thats why right we are hearing from the beginning they were injecting water than circulating coolant. I very much doubt back up battery substitutes for anything other than critical communication, panel lighting 24 V or 12 V founctions and certainly for some injection pumps, but nothing more. Will be glad though to know if there's more these systems do.

[Lalmohan]

reports indicated that the batteries kept the plant operational for 4 hrs or so, near the start of this thread somewhere

[Amber G.]

It appears there are now trace amounts of strontium being found. Lets see if the reports are confirmed.
Slight Amounts of Strontium Found

Sr-90, of course is worse, long half life (30 Years) and it goes in bones and stays..Unlike Cs which has a biological half life of a month or so.

[Amber G.]

reports indicated that the batteries kept the plant operational for 4 hrs or so, near the start of this thread somewhere

That is true (as in what I heard too ) At that time experts were guessing they can go may be 12 hours or so but they must get diesel power fairly soon.

[harbans]

reports indicated that the batteries kept the plant operational for 4 hrs or so, near the start of this thread somewhere

Lal Ji, it would have kept only very critical aspects operational. Nothing more. Ship Diesels can produce 20-30 MW of power for example, and if NPPs use that sort of power for operations one does'nt expect backup Batteries packs to sustain all process operations. Keeping the plant "operational" might imply just critical/ special/ emergency functions only till main power is restored. And thats where they faced the problem, when Back Generators could not be plugged in due to some incompatibility.

[Theo_Fidel]

The batteries don't have to & don't power the entire building. Even emergency lighting is on its own battery pack. AFAIK the batteries definitely operate the essential pumps that's why I said we have to see if they were able to do so when the report comes out.

Take a look at page 10 of the Areva presentation. The only pump needed is the one to supply water for the heat exchanger/wet well cooling. Everything else is more or less self driven by valves. It is the dying of the condenser/wet well pump when the batteries died that caused the problems. Essentially one pump. The last line of defense. IIRC the amount of water needed for the condenser was about 200 tonnes per day. A bucket brigade could handle that. The wet well does not need even that.

The odd thing is if this were a sodium coolant reactor it is not pressurized and is easily passively cooled. We would not be having this conversation.

http://www.fairewinds.com/sites/default ... ushima.pdf

[Mort Walker]

I read 8 hours, and I'll have to find the link. In any case, even 4 hours is pretty good for operating the cooling systems. If the EG systems were better placed or protected, a lot of this would not have happened.

[Lalmohan]

anyways, those figures are from the governmint'
an' ye don't believe what the governmint says, now do ya?

[Amber G.]

I read 8 hours, and I'll have to find the link. In any case, even 4 hours is pretty good for operating the cooling systems. If the EG systems were better placed or protected, a lot of this would not have happened.

Remember 8 hours too (but as Mort says, for discussion it does not make much difference .. it is of the this order.. before you have to get DG fired up)

[Amber G.]

anyways, those figures are from the governmint'
an' ye don't believe what the governmint says, now do ya?

Yeah . ..( but they are checked, and tested periodically)

[Theo_Fidel]

So the entire thing rested on the generators coming on. What were they thinking. Single point of failure and six sigma don't mix. From experience generators are highly unreliable. I had one for a 911 facility that would keep dying on still days because it would choke on its own exhaust!

[Mort Walker]

^^^No, you build a 190 MW generator that is nuclear powered one and put it on a Nimitz class ship.

[Mort Walker]

So the entire thing rested on the generators coming on. What were they thinking. Single point of failure and six sigma don't mix. From experience generators are highly unreliable. I had one for a 911 facility that would keep dying on still days because it would choke on its own exhaust!

The whole of India is literally powered by diesel generators as commercial power is unreliable for critical applications. You choke on exhaust or energetic particles, so pick your poison, and so far very few people have died from NPPs in comparison to natural gas (don't forget Deep Water Horizon), coal (no need to mention how many have died in that) and oil exploration. Even Chernobyl is now a wild life preserve.

[Amber G.]

.. so pick your poison, and so far very few people have died from NPPs in comparison to natural gas (don't forget Deep Water Horizon), coal (no need to mention how many have died in that) and oil exploration. Even Chernobyl is now a wild life preserve.

Mort - Taking data from UCS (Union of Concerned Scientists - Considered by many as some what anti-nuclear group):
>>>
For reactor meltdown to be as harmful as coal-burning, we would need a meltdown every six months
(Other estimates, gives about one every two weeks)

Data from a paper but don't take my word for it, do your own calculations...(or check any reliable sources for the data) and post your own numbers..

(UCS estimates one meltdown per 2,000 plant-years and it estimates around 5,000 deaths per melt down and 45,000 extra cancer deaths in a population of ten million over 50 years etc...(I will not put all the numbers here one can get these numbers easily..)
( certainly NOT a low figure from what we have seen in last few meltdown )... And Coal data EPA etc ..)

Happy calculating...

[arnab]

^^^No, you build a 190 MW generator that is nuclear powered one and put it on a Nimitz class ship.

Sir you raise an issue that I have been wondering about. Perhaps the gurus can answer. How are our nuke sub reactors (Arihant and Nerpas) designed to react to LOCAs? I do understand that they are not going to be impacted by tsunamis - but presumably they have some sort of battery back ups or passive cooling systems? Does anyone know?

Was reminded of the Soviet K19 incident in the 1960s

K-19 submarine reactor accident, 1961 Date: 4 July 1961

Location: North Atlantic Ocean, aboard USSR ballistic missile submarine K-19

Type of event: submarine reactor accident

Description:

A reactor accident occurred on the USSR ballistic missile submarine K-19 while it was on exercises in the North Atlantic. The K-19 (hull number 901) was the lead ship of the Project 958 (Hotel I) class, launched 8 April 1959 and commissioned 12 November 1960; it carried three R-13 SLBMs. On 4 July 1961 a leak developed at an inaccessible part of the primary cooling circuit, causing a sudden pressure drop and triggering emergency systems. The crew improvised a system to supply coolant, involving prolonged exposure to radioactive steam and other gases in the reactor compartment. Eight crew members sustained doses of 5,000 to 6,000 rem; the rest of the crew sustained significant doses as well (at least 100 rem). A diesel submarine evacuated the crew, and the K-19 was towed back to the Kola Peninsula. For the eight crewmembers with fatal doses, time from exposure to death in days was 6, 6, 6, 8, 9, 11, 16, and 19. The remaining crew were hospitalized with radiation sickness until September. Replacement of the reactor compartment was completed from 1962 to 1964, and the two damaged reactors were dumped in Abrosimova Bay in the Kara Sea.

Consequences: 8 fatalities, at least 31 injuries.

[Amber G.]

Just took a dekho at wiki's "banana dose equivalent" page.. It got hijacked by a few and became completely useless ..."Geoff Meggitt (former UK Atomic Energy Authority)" footprints everywhere.. (Theoji post reminded me as if it was lifted straight from there) ... lot of activity, according to history, since it was mentioned in brf ..

(It was fairly well written when Ramana put a link, and I checked)

See this there now:

This article or section is in need of attention from an expert on the subject.
The following WikiProjects or Portals may be able to help recruit one:

• WikiProject Health· Health Portal • WikiProject Physics· Physics Portal • WikiProject Energy· Energy Portal
If another appropriate WikiProject or portal exists, please adjust this template accordingly

For the record, and benefit for all let me put it again here: (From an old copy)

A banana equivalent dose is a concept occasionally used by "resident physicists" to place in scale the dangers of radiation by comparing exposures to the radiation generated by a common banana.

Many foods are naturally radioactive, and bananas are particularly so, due to the radioactive potassium-40 they contain. The banana equivalent dose is the radiation exposure received by eating a single banana. Radiation leaks from nuclear plants are often measured in extraordinarily small units By comparing the exposure from these events to a banana equivalent dose, a more intuitive assessment of the actual risk can sometimes be obtained.

The average radiologic profile of bananas is 3520 picocuries per kg, or roughly 520 picocuries per 150g banana. The equivalent dose for eating 1 banana is 0.1 muSV.

Bananas are radioactive enough to regularly cause false alarms on radiation sensors used to detect possible illegal smuggling of nuclear material at US ports

Yeah...people forgetting that its just a unit.. as much as horse has to do with horsepower..some actually putting all that nonsense about that K-40 cycle in the body etc... I'll see how long does it take before wiki gets fixed.

[Amber G.]

How are our nuke sub reactors (Arihant and Nerpas) designed to react to LOCAs? I do understand that they are not going to be impacted by tsunamis - but presumably they have some sort of battery back ups or passive cooling systems? Does anyone know?

Short answer - I don't know. Some guesses which may be of interest.

1. Power requirement are much smaller. (Much smaller size, and LOCA requirements are much smaller)

2. Physically small and produce relatively high power for each unit of space - design is more for reliability and less for efficiency

3 The fuel used is typically of higher enrichment .. (I am not sure how much it is true for all but for some US IIRC one had 90+% enriched U235. .. Core is MUCH smaller)

4. The fuel is not UO2 but U-zirconium alloy (? - Again it may be true for only some US submarines) In any case they are designed for a long core life (incorporating burnable neutron poisons, internal neutron shield etc...)

5. Whole vessel can probably remain floating (or buried in water) without LOCA as long as it is sealed.

you build a 190 MW generator that is nuclear powered one and put it on a Nimitz class ship

Mort - I think Russia has plans to build floating nuclear power plants for land..