Japan Earthquake: Nuclear Plants at Fukushima Daiichi

In summary: RCIC consists of a series of pumps, valves, and manifolds that allow coolant to be circulated around the reactor pressure vessel in the event of a loss of the main feedwater supply.In summary, the earthquake and tsunami may have caused a loss of coolant at the Fukushima Daiichi NPP, which could lead to a meltdown. The system for cooling the reactor core is designed to kick in in the event of a loss of feedwater, and fortunately this appears not to have happened yet.
  • #71
NHK TV showing video of smoke rising from Fukushima Daichi No 3
http://www.kcet.org/disasterinjapan/ [Broken]
 
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Engineering news on Phys.org
  • #72
Just how do you compare CPM and MicroSV? Answer: you don't without calibration standards. One is relative response to unknown source and the other is Dose. Sounds like technician talk!
 
  • #73
Guys. Supposed the fuel rods melted and become molten, do fission still occur in molten state or not anymore?
 
  • #74
rogerl said:
Guys. Supposed the fuel rods melted and become molten, do fission still occur in molten state or not anymore?

Immediately after the quake, the control rods were automatically inserted, and the fission chain reaction stopped. The heat production now is due to decay of the radioactive fission products, and is only about 10 % of the power when the reactor is on.
 
  • #75
PietKuip said:
Immediately after the quake, the control rods were automatically inserted, and the fission chain reaction stopped. The heat production now is due to decay of the radioactive fission products, and is only about 10 % of the power when the reactor is on.

I know. But supposed the controls rods were not inserted and the fuel rods melt and become molten and there is a tough cement underneath that prevent further falling underneath the plant. Would the uranium still fission when it's already in the molten state or would fission only occur when the uranium is solid?
 
  • #76
For fission it doesn't matter whether the fuel is solid or melted.
 
  • #77
rogerl said:
I know. But supposed the controls rods were not inserted and the fuel rods melt and become molten and there is a tough cement underneath that prevent further falling underneath the plant. Would the uranium still fission when it's already in the molten state or would fission only occur when the uranium is solid?
The fission reaction would have eventually stopped but more slowly since the core configuration would have been disrupted. During operation of a BWR, some control rods are in the core for control of reactivity, i.e., to keep the core critical at steady state. The control rods are gradually withdraw during the cycle as the enriched uranium is depeleted (consumed) in a carefully devised sequence such that the core is always just near critical, otherwise the power is slowing increasing or decreasing depending on the need for power increase or decrease. Toward end of cycle, when much of the fissile material has been used, the control rods are all out (all rods out, ARO). The reactor can continue for some days afterward, and then it is shutdown for refueling and maintenance.

If the fuel melted it would displace the water and reduce the moderation, which would make the core slightly subcritical at some point in time, and the fission reaction would decrease.

However, we know that the control rods did insert in the Fukushima reactors, and the fission reactions ceased. The problem is that fission products continue to decay after the fission reaction is stopped, and that heat must be removed from the core/fuel following shutdown. The heat removal did occur for sometime after shutdown, first using power from emergency diesel generators, and then on batteries. However, at some point the cooling capacity was reduced or lost and some part of the core overheated.

Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

From the continuity of matter property, what goes into a system, must come out elsewhere if mass in the system is constant. So, if some seawater goes in, it must come out somewhere as water or steam. It is the steam that is occasionally vented to keep the pressure down. However, this means that the system is no longer closed to the environment, and some fission products, mostly gases Xe and Kr, and perhaps some volatiles, e.g., I, will escape to the atmosphere.

The objective now is to cool the reactor core and minimize the release of radioactive substances to the environment.
 
  • #78
Astronuc said:
Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

I still haven't found out what exactly they flooded with sea water.
Do they just replace lost water in the RPV by sea water? Or are they trying to cool the RPV from the outside by flooding the containment? Or both?
The use of boron suggests the former but I keep hearing about the latter.

Does anybody know more?
 
  • #79
Astronuc said:
The fission reaction would have eventually stopped but more slowly since the core configuration would have been disrupted. During operation of a BWR, some control rods are in the core for control of reactivity, i.e., to keep the core critical at steady state. The control rods are gradually withdraw during the cycle as the enriched uranium is depeleted (consumed) in a carefully devised sequence such that the core is always just near critical, otherwise the power is slowing increasing or decreasing depending on the need for power increase or decrease. Toward end of cycle, when much of the fissile material has been used, the control rods are all out (all rods out, ARO). The reactor can continue for some days afterward, and then it is shutdown for refueling and maintenance.

If the fuel melted it would displace the water and reduce the moderation, which would make the core slightly subcritical at some point in time, and the fission reaction would decrease.

However, we know that the control rods did insert in the Fukushima reactors, and the fission reactions ceased. The problem is that fission products continue to decay after the fission reaction is stopped, and that heat must be removed from the core/fuel following shutdown. The heat removal did occur for sometime after shutdown, first using power from emergency diesel generators, and then on batteries. However, at some point the cooling capacity was reduced or lost and some part of the core overheated.

Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

From the continuity of matter property, what goes into a system, must come out elsewhere if mass in the system is constant. So, if some seawater goes in, it must come out somewhere as water or steam. It is the steam that is occasionally vented to keep the pressure down. However, this means that the system is no longer closed to the environment, and some fission products, mostly gases Xe and Kr, and perhaps some volatiles, e.g., I, will escape to the atmosphere.

The objective now is to cool the reactor core and minimize the release of radioactive substances to the environment.

So, when the news reports that there is a danger of radiation exposure...what exactly is being exposed? I think I know the very basics of the core, which is essentially uranium fuel rods that are bombarded by free neutrons right? Where does Xe, Kr, and I come from? Are these what uranium decays too? When people get radiation sickness/exposure, what is harming them? electromagnetic radiation or something else?

Clearly I have no clue what I'm talking about, but I would like too.
 
  • #80
Hypothetical People external to the plant and workers (real) near or within the plant would be the things being exposed to radiation. Eventhough the melted fuel losses its favorable geometry for substained criticality, some neutrons and high energy gammas will continue to prolong the fission process, but at a significantly lower pace and would be considered subcritical. The attached link discusses the fission fragment spectrum of radioisotopes.

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html
 
  • #81
nlsherrill said:
So, when the news reports that there is a danger of radiation exposure...what exactly is being exposed? I think I know the very basics of the core, which is essentially uranium fuel rods that are bombarded by free neutrons right? Where does Xe, Kr, and I come from? Are these what uranium decays too? When people get radiation sickness/exposure, what is harming them? electromagnetic radiation or something else?

Clearly I have no clue what I'm talking about, but I would like too.
Steam from the primary system would carry Xe and Kr (noble) gases, and perhaps some I and Br which are volatiles. It is expected that I and Br would form oxides, and react chemically to form iodates and bromates, if not iodides and bromides.

Xe, Kr, I, Br are fission products produced when U-236 (U235+n) fissions. There are other fission products such as Cs, Ba, La, . . . . and Rb, Sr, Y, . . . which are essentially in solid form, and the unused U, Pu, . . . which is in the fuel. Normally these are surrounded by a metal alloy of Zr, but that alloy has probably corroded/oxidized, and no longer performs its function, which is the keep the fuel (UO2 and fission products) separated from the coolant.

The fuel and fission products can oxidize into particles on the order of several microns, and this can be then dispersed in the coolant.

The noble gases can readily escape into the steam, and it is hoped that much of the fuel will remain intact.

There are also core components, e.g. control rods, and other structures that are made of stainless steel, typically SS304. The control rods contain boron carbide (B4C) and perhaps Hf, which are neutron absorbers used to control/limit the fission reaction or shutdown the reactor. If the temperatures in the core got to ~1300-1400 C, then the control rods could have melted. Above 1000 C, they could have gotten soft and deformed.

When people are exposed to radiation, it is usually beta and gamma radiation, or possibly alpha particles if isotopes of heavy elements, e.g., Rn, Ra, U or tranuranics were ingested or inhaled. Alpha particles are stopped by clothing or skin. Beta particles are more penetrating, and gamma photons are the most penetrating.

Ionizing radiation harms cells by radiolysis of the water (which forms peroxide and hydrogen), which can then chemically react with the complex molecules like DNA, RNA, proteins, vitamins, enzymes, coenzymes, . . . . which are necessary for cells to function.

A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced.
 
  • #82
Borek said:
For fission it doesn't matter whether the fuel is solid or melted.

Borek: I think the question is (at least mine is. . . ) this: if the core melts and becomes a molten mixture of fissile materials + melted control rods, even if the reactor's fuel has been "killed" with sea water and boron, is it still possible that the molten mixture might become "critical"?

And even if not, how long will the ongoing heat of decay (at 10% of the level of an operational reactor mentioned) persist in the absence of cooling water?

Finally, are either the primary steel containment vessel or the reinforced concrete secondary containment, or both up to the task of containment of a core meltdown and if so, for how long?
 
  • #83
LanceV said:
I still haven't found out what exactly they flooded with sea water.
Do they just replace lost water in the RPV by sea water? Or are they trying to cool the RPV from the outside by flooding the containment? Or both?
The use of boron suggests the former but I keep hearing about the latter.

Does anybody know more?
As far as I know, they were trying to inject seawater into the pressure vessel, ostensibly through the piping system used by the ECCS. Flooding containment is also a possibility, but that's mostly outside of the RPV which contains the core, and which is where the cooling water must go.

The steam is venting somehow, through pressure relief valves, and then the personnel have to vent the containment. So the seawater goes in, and some steam comes out, and there has to be a mass balance.

How they are cooling the seawater once it's heated is not clear.

If they pump seawater into the RPV/primary system, and it is flowing out into containment, that could mean an open valve or pipe break. HOWEVER, there is no information about the integrity of the RPV or piping within containment. We can only wait for further information from the site.
 
  • #84
well as a civil defence member (non physicist member) i don't think the risk is high at all, but in its history now is the closest to a risk there has been as far as i am aware. they will properly have to cold start it (i think no facts to back that up) which is very expensive and take months. i am surprised World Agency of Planetary Monitoring and Earthquake Risk Reduction,(WAPMERR) has said nothing at all. oh and the chance even if it was to go of a thermal explosion is so small it is practically 0
 
  • #85
Astronuc said:
Flooding containment is also a possibility, but that's mostly outside of the RPV which contains the core, and which is where the cooling water must go.

Yes, but the question is can they inject water into the core? Maybe the pressure is to high. Or there is a danger of explosion when water hits the hot fuel rods.

Astronuc said:
The steam is venting somehow, through pressure relief valves, and then the personnel have to vent the containment. So the seawater goes in, and some steam comes out, and there has to be a mass balance.

At first I was under the impression that the sea water is circulated through the reactor. Maybe by extracting it via the suppression pool and then back into the sea. If the core is not molten this would probably result in only a minor pollution.

But it is hard to find any definite information. It seems that there is nobody twittering from the control room. Maybe they are busy atm.
 
  • #86
if it was they would circle the rods not by direct contact but by going around it as such, and when it cools down then flood it or there would be a large cloud were they stand. slow cool then rapid cool can't remember the real name for it but i think you may understand
 
  • #87
I just noticed that in Ibaraki which is maybe 50 km south of Fukushima, ambient dose rates are rising (to about 180 nGy/h) for the first time since the earthquake. Apparently, the wind is turning.

See:
http://www.bousai.ne.jp/eng/ [Broken]

For Fukushima itself, values are still not available on that site.
 
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  • #88
misnderstudge said:
if it was they would circle the rods not by direct contact but by going around it as such, and when it cools down then flood it or there would be a large cloud were they stand. slow cool then rapid cool can't remember the real name for it but i think you may understand
Maybe one is thinking of reflood or quenching (rapid cooling).

The details for each unit are different and unknown.

Apparently Units 1 and 3 lost EDGs and/or electrical buses between EDGs and ECCS due to tsunami. The tsunami did take out some of the fuel systems for the EDGs, but also may have damaged the electrical equipment.

As far as I know, they are pumping water through the piping in order to cool the core, and/or they are flooding the primary containment.

We lack the details, so we don't know what systems are available.


Apparently the US 7th Fleet has detected radiation at sea and are moving out of the area.

Any sustained activity offsite is a bit worrisome because it means radioactivity is getting of site in significant (not quantified) amounts.

WorldNuclearNews said:
Onagawa 'emergency'

A technical emergency was declared at 12.50pm today at the Onagawa nuclear power plant after radiation levels in the plant site reached 21 microSieverts per hour. At this level plant, owner Tohoku Electric Power Company is legally obligated to inform government of the fact. Within just ten minutes, however, the level had dropped to 10 microSieverts per hour.

. . . .
The increase in radioactivity at Onagawa has been attributed to releases from Fukushima.

WorldNuclearNews said:
Potential contamination of the public is being studied by Japanese authorities as over 170,000 residents are evacuated from within 20 kilometres of Fukushima Daini and Daiichi nuclear power plants. Nine people's results have shown some degree of contamination.

Japan's Nuclear and Industrial Safety Agency (Nisa) – part of the Ministry of Economy, Trade and Industry (Meti) – said that out of about 100 residents evacuated from Futaba by buses, nine people were found to have been exposed. The pathway of their exposure is currently under investigation.

One person was measured to have an exposure of 18,000 counts per minute (cpm); another had a measurement of between 30,000 and 36,000 cpm; while a third evacuee had an exposure of 40,000 cpm. A fourth person initially gave a reading of over 100,000 cpm, but a second measurement taken after the person had removed their shoes was just under 40,000 cpm. Another five people were said to have "very small counts".Radiation levels have been monitored across the Fukushima Daiichi and Daini sites. As of 10.00pm today, Tepco said that radiation levels were lower and stable. The maximum level detected on the 12 March was at 3.29pm when levels reached 1015 microsieverts per hour.

On-site casualties

At Fukushima Daiini unit 3 one worker received a radiation dose of 106 mSv. This is a notable dose, but comparable to levels deemed acceptable in emergency situations by some national nuclear safety regulators.
. . . .
Source: http://www.world-nuclear-news.org/RS-Contamination_found_on_evacuated_residents-1303114.html

Some colleagues indicated that World Nuclear News is one of the best sites for information on the ongoing situation.
 
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  • #89
"A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced."

Considering human evolution occurred during higher levels of terrestrial radiation in the far past, More than a little radiation exposure is not that concerning, except for the weak. I and many of my fellows Nukes have life-time whole body doses exceeding 40 Rem, and are relatively healthy at our retirement ages.
 
  • #91
Old news, but insight to US Actions at West Coast Nuclear Pwr Plants (all PWRs):

http://pbadupws.nrc.gov/docs/ML1107/ML110700503.pdf"
 
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  • #92
Reno Deano said:
"A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced."

Considering human evolution occurred during higher levels of terrestrial radiation in the far past, More than a little radiation exposure is not that concerning, except for the weak. I and many of my fellows Nukes have life-time whole body doses exceeding 40 Rem, and are relatively healthy at our retirement ages.
I have also been exposed to radiation well beyond what the average person in the general population would receive, and I'm fine.

On the other hand, I've had one colleague develop thyroid problems, possibly related to exposure.

Still, the industry doesn't need to be unnecessarily exposing the general population (especially pregnant women, babies and children) to radiation - as is currently the case. :grumpy:
 
  • #93
Apparently the US 7th Fleet has detected radiation at sea and are moving out of the area.

Knowing the Navy they flew through the downwind radionuclide concentrations and brought it back aboard the ship. Some of the highest contamination found external of the reactor compartments on an aircraft carrier is the fresh air intake filters for the ship. When planes lands they shake off accumulated contamination (Cs-137 and other radionuclide's) from their high altitude flights, which is quickly sucked into the fresh air plenums outboard of the flight deck.
 
  • #94
''When planes lands they shake off accumulated contamination (Cs-137 and other radionuclide's) from their high altitude flights ..."

Is the contamination distribution denser at high altitudes (and up into the jet stream) or do the planes come back with greater contamination because of their path length through the contaminated air being longer?
 
  • #95
Latest reports of Japan officials bowing in unison to express their remorse and other discouraging comments about the status of all three reactors have me feeling like its game over.

No water>no coolant>2200F+ temperatures>?

Is it inevitable at this point?
 
  • #96
Is the contamination distribution denser at high altitudes (and up into the jet stream) or do the planes come back with greater contamination because of their path length through the contaminated air being longer?

Its the path length and time immersed. There is long lived 1950's & 1960's weapons testing contamination circulating around up there.
 
  • #97
Reno Deano said:
Its the path length and time immersed. There is long lived 1950's & 1960's weapons testing contamination circulating around up there.

I don't think the fission products of the 50s and 60s tests contribute any relevant amount of contamination to these flights. My impression is that the fallout from the atmospheric tests (and other inputs) rain out to the earth’s surface largely within a year or so of their input. Events such as large forest fires can return small but measurable amounts of this 60s fallout back into the atmosphere.

However, I would bet that the current contamination of US aircraft spoken of is >99% sourced to current reactor issues in Japan and not appreciably due to 50s/60s era sources.
 
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  • #98
Astronuc said:
Is one referring to Onagawa plant? What is meant by enhanced?

There is some concern about the spent fuel pool at FK-I, Unit 1 and whether or not it went dry. I would hope they have checked that.
I have been looking for info on the risks of a dry spent fuel pool. Unfortunately, there is little middle-of-the road info out there. Lots of the worst-case scenarios, though many of them have the fingerprints of Fairewinds Associates on them. Phrases like "Chernobyl on steroids" etc. The NRC materials I found were comforting about the level of safety required, but very light on the risks.

This software simulator site quiz says that the severity of an SFP failure would be on a par with a "worst case power accident".
http://www.microsimtech.com/sfpquiz/default.htm [Broken]

Can you help clarify, Astro?
 
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  • #99
I think the worst case scenario for a 'dry spent fuel pool' is overheating to the point where the zirc cladding oxidizes rapidly (in other words, it burns). If you are old enough, you may remember seeing a zirconium fire - the old flashbulbs (think reporters with big crown graphic 4x5 cameras) used zirconium wire. The good news is that, as long as the pool is intact, all you need to do to prevent the 'dry' part of the scenario is add water to make up for any boiloff.
 
  • #100
In a nuclear reactor, there are as many as a thousand fuel rods. But there only appears to be a dozen or so control rods which are put amongst the thousands of fuel rods. How does this stop nuclear reaction within each rod? Or in a nuclear reactor. Do neutrons from different fuel rods hit other fuel rods at a distance and the control boron rods are supposed to block or absorb them? But how can the few control rods absorb the neutrons from thousands of fuel rods?
 
  • #101
Layman's question...doesn't the rate of radiation greatly increase when a core melts into a blob at the bottom of the reactor because of the inverse square law? So wouldn't a lone melted rod give off much less radiation than a bunch of them?

And at what time is the maximum amount of radiation released? Pre-core meltdown when all coolant is gone? Post?

Thanks for the help!
 
  • #102
falcon32 said:
Layman's question...doesn't the rate of radiation greatly increase when a core melts into a blob at the bottom of the reactor because of the inverse square law? So wouldn't a lone melted rod give off much less radiation than a bunch of them?

And at what time is the maximum amount of radiation released? Pre-core meltdown when all coolant is gone? Post?

Thanks for the help!
No, the radiation source is independent of geometry, and only dependent on the fission products or nature of the radionuclides decaying. If one looks at the decay heat curve as a function of time, one sees that it is decreasing, and the radionuclides decay to long-lived radionuclides, or inert (non-radioactive) nuclides.

The maximum release would be dependent on a number of variables including the fission product inventory (source term) and the rate at which fuel rods are breached.
 
  • #103
rogerl said:
In a nuclear reactor, there are as many as a thousand fuel rods. But there only appears to be a dozen or so control rods which are put amongst the thousands of fuel rods. How does this stop nuclear reaction within each rod? Or in a nuclear reactor. Do neutrons from different fuel rods hit other fuel rods at a distance and the control boron rods are supposed to block or absorb them? But how can the few control rods absorb the neutrons from thousands of fuel rods?
In a BWR, there is one control rod for four fuel assemblies. Most modern BWRs use a 10x10 array of fuel rods, but some fuel rods are part-length rather than full-length (core height), and there are 'water rods' or 'water channels' within the assembly in order to introduce water for moderation in the interior rods of the assembly. So while a 10x10 fuel assembly has 100 lattice positions, some designs have 96 rods, some 91 rods, and other 92 rods, and some of those fuel rods might be 2/3 of the full-length or core height.

The are local differences in neutron flux and power generation, which is more or less proportional to local neutron flux (we call this power peaking, and we can describe local power in terms of an average power and local peaking factor). The fuel rods in the four assemblies are most affected by the control blades, while those on the opposite side of the fuel assembly are less affected - but that is only important when the reactor is critical, and then only when the reactor is at power.

We know the control rods were inserted, which means the fission reaction shutdown, i.e. the fission reaction or power geneation went to essentially zero. However as mentioned elsewhere, there is decay heat from the beta and gamma decay of fission products, which decay well after the fission reactions stop.

Control rods contain a neutron absorber B-10 and/or Hf, which is very efficient at absorbing neutrons. The B-10 is a much better absorber of neutrons than U-235 or Pu-239, so the cores are always designed such that when the control rods are inserted, minus the strongest control rod, the core goes subcritical. Core and fuel design is a very mature technology.
 
  • #104
Core covered with seawater, and still a continuing melt and release of vapors? Sounds like something is missing, such as a control rod or 2, or the core was never covered. BTW, salt water is a great neutron moderator. Remember BWR control rods need to be held "up" inplace by an intricate hydraulic system.

BWR system description: http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf"
 
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  • #105
Dumb question time (but its the right forum for it I guess)
Where have I gone wrong with this.
If the fuel rods in the core are about 1300K then pluggin into stefan boltman I get
At 1300K I a get c 1.62*10^5 J/s per square meter assuming emissivity of 1.
j = (1300K)^4* 1 * (5.67*10^-8)

So why has there not been a reasonable amount of cooling due to radiative rather than conductive heat transfer? Have I got the calculations wrong?
 
<h2>1. What caused the Japan earthquake and subsequent nuclear disaster at Fukushima Daiichi?</h2><p>The Japan earthquake, also known as the Great East Japan Earthquake, was caused by a massive underwater earthquake that occurred on March 11, 2011. The earthquake had a magnitude of 9.0 and was the strongest ever recorded in Japan. The earthquake triggered a massive tsunami, which caused extensive damage to the Fukushima Daiichi nuclear power plant and led to a nuclear disaster.</p><h2>2. What is the current status of the nuclear reactors at Fukushima Daiichi?</h2><p>As of now, all of the nuclear reactors at Fukushima Daiichi have been shut down and are no longer in operation. However, the site is still being monitored for radiation levels and there is an ongoing effort to clean up the radioactive materials that were released during the disaster.</p><h2>3. How much radiation was released during the Fukushima Daiichi nuclear disaster?</h2><p>According to the International Atomic Energy Agency, the Fukushima Daiichi nuclear disaster released an estimated 10-15% of the radiation that was released during the Chernobyl disaster in 1986. However, the exact amount of radiation released is still being studied and debated.</p><h2>4. What were the health effects of the Fukushima Daiichi nuclear disaster?</h2><p>The health effects of the Fukushima Daiichi nuclear disaster are still being studied and monitored. The most immediate health impact was the evacuation of approximately 160,000 people from the surrounding areas to avoid exposure to radiation. There have also been reported cases of thyroid cancer and other health issues among those who were exposed to the radiation.</p><h2>5. What measures have been taken to prevent future nuclear disasters in Japan?</h2><p>Following the Fukushima Daiichi nuclear disaster, the Japanese government has implemented stricter safety regulations for nuclear power plants and has conducted stress tests on all existing plants. They have also established a new regulatory agency, the Nuclear Regulation Authority, to oversee the safety of nuclear power plants. Additionally, renewable energy sources are being promoted as a more sustainable and safer alternative to nuclear power in Japan.</p>

1. What caused the Japan earthquake and subsequent nuclear disaster at Fukushima Daiichi?

The Japan earthquake, also known as the Great East Japan Earthquake, was caused by a massive underwater earthquake that occurred on March 11, 2011. The earthquake had a magnitude of 9.0 and was the strongest ever recorded in Japan. The earthquake triggered a massive tsunami, which caused extensive damage to the Fukushima Daiichi nuclear power plant and led to a nuclear disaster.

2. What is the current status of the nuclear reactors at Fukushima Daiichi?

As of now, all of the nuclear reactors at Fukushima Daiichi have been shut down and are no longer in operation. However, the site is still being monitored for radiation levels and there is an ongoing effort to clean up the radioactive materials that were released during the disaster.

3. How much radiation was released during the Fukushima Daiichi nuclear disaster?

According to the International Atomic Energy Agency, the Fukushima Daiichi nuclear disaster released an estimated 10-15% of the radiation that was released during the Chernobyl disaster in 1986. However, the exact amount of radiation released is still being studied and debated.

4. What were the health effects of the Fukushima Daiichi nuclear disaster?

The health effects of the Fukushima Daiichi nuclear disaster are still being studied and monitored. The most immediate health impact was the evacuation of approximately 160,000 people from the surrounding areas to avoid exposure to radiation. There have also been reported cases of thyroid cancer and other health issues among those who were exposed to the radiation.

5. What measures have been taken to prevent future nuclear disasters in Japan?

Following the Fukushima Daiichi nuclear disaster, the Japanese government has implemented stricter safety regulations for nuclear power plants and has conducted stress tests on all existing plants. They have also established a new regulatory agency, the Nuclear Regulation Authority, to oversee the safety of nuclear power plants. Additionally, renewable energy sources are being promoted as a more sustainable and safer alternative to nuclear power in Japan.

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