**4. Discussion on the possible management problems after March 11, 2011**

#### **4.1. Missed chances to reduce the contamination level**

The nuclear accidents in Chernobyl and in Fukushima have caused huge contamination of cities, villages and land and had necessitated the evacuation of ten-thousands of people a fraction of which in case of Chernobyl had received hazardous radiation.

In case of a such nuclear accident, there are two aspects which require immediate action:


The groundwater should never become a problem for the reactor by installing deep water-

The successive hydrogen explosions, which destroyed a part of the reactors and their roofs, should have been prevented by hydrogen detectors, which raise an alarm and which activate

be kept below the explosion level of 4% in air, this value depending on humidity and other factors. The alternative of Passive Autocatalytic (Hydrogen) Recombiners (PAR) [13] does not require electricity to operate and has been installed in some reactors worldwide. PAR had been applied in the Three-Mile-Island accident (March 28, 1979) to reduce the hydrogen content in a hydrogen bubble inside the reactor chamber to prevent a large explosion. Hydrogen

After the initial weeks following the accident, large amounts of cooling water had been pumped into the reactors, for example, 300 metric tons per day, which initially was further

water, it could not be stopped. Half of the water returning from reactor cooling was filtered and partially decontaminated and returned for cooling, and the other half of 200 m3

collected daily in large storage tanks in the plant surroundings for later treatment. A fraction

Decontamination of water was problematic. Equipment from France, USA and Japan had been applied using reverse osmosis, adsorption by zeolites or evaporation of salt water.

groundwater. Despite large efforts taken to reduce the influx of ground-

removal works even in the presence of CO which is frequently formed in fires [14].

. Hydrogen concentration should always

Experiences from the Fukushima Disaster http://dx.doi.org/10.5772/intechopen.77726 93

was

tight barriers around the reactor area, before the reactor starts to work.

**Figure 3.** Schematic view of suction of radioactive cloud and sprinkling with seawater.

valves for high-pressure injection of nitrogen or CO<sup>2</sup>

**4.2. The contaminated water problem**

of this tank collection is shown in **Figure 4**.

diluted with 400 m3

If a long-lasting fire occurs as in Chernobyl, where the graphite moderator burnt and sent radioactive clouds very high so that contamination spread over large distances or in case of Fukushima, where the cloud left the reactor building and was carried by wind, intensive suction should be considered. **Figure 3** schematically shows the reactor building with attached large-diameter steel pipes which collect the cloud by a powerful ventilator of at least 5000 m3 per hour depending on tube diameter. A sprinkler system condenses the radioactive vapors and particles, and this contaminated water should then flow into the sea reservoir or into a basin. In case of Fukushima, this contaminated water should in the first phase have been transported by long pipes to the Kuroshio current where it is diluted. In the second phase, the gaps of 100 and 140 m between the existing seawalls/breakwaters could have been closed and water could have been pumped out to the basins where it could be collected and stored for later treatment. The intense spraying followed by the suction activity would have reduced the extended radioactive spreading and thus the evacuation requirements. Such suction systems could also be useful in case of accidents and fires in chemical factories and in oil refineries.

Reactor surrounding should always be covered by a thick concrete layer with a slope of 2–3° in the direction of the sea or the basin, so that all water is controlled and collected and the soil cannot be contaminated.

**Figure 3.** Schematic view of suction of radioactive cloud and sprinkling with seawater.

The groundwater should never become a problem for the reactor by installing deep watertight barriers around the reactor area, before the reactor starts to work.

The successive hydrogen explosions, which destroyed a part of the reactors and their roofs, should have been prevented by hydrogen detectors, which raise an alarm and which activate valves for high-pressure injection of nitrogen or CO<sup>2</sup> . Hydrogen concentration should always be kept below the explosion level of 4% in air, this value depending on humidity and other factors. The alternative of Passive Autocatalytic (Hydrogen) Recombiners (PAR) [13] does not require electricity to operate and has been installed in some reactors worldwide. PAR had been applied in the Three-Mile-Island accident (March 28, 1979) to reduce the hydrogen content in a hydrogen bubble inside the reactor chamber to prevent a large explosion. Hydrogen removal works even in the presence of CO which is frequently formed in fires [14].

#### **4.2. The contaminated water problem**

**4. Discussion on the possible management problems after** 

fraction of which in case of Chernobyl had received hazardous radiation.

The nuclear accidents in Chernobyl and in Fukushima have caused huge contamination of cities, villages and land and had necessitated the evacuation of ten-thousands of people a

**1.** Can the fission rate and the development of uncontrolled heating of the fuel rods be stopped from the control room or by remote actions to lift the fuel rods or by introducing neutron-absorbing elements or compounds based on boron, silver, cadmium and indium combined with intensive cooling, decisions to be made immediately by an experienced

**2.** In case of fire or escaping flames and clouds, the collateral damage by widespreading of radioactivity has to be minimized by very intense water spraying using any water resources, be it from nearby lake or river or sea and using water pumps and high-power water guns powered from pre-installed and mobile diesel generators. When a natural water source cannot be reached, then the installation of a nearby pond of sufficient volume should be arranged near all reactors. Contamination of the sea is less harmful than contamination of cities, villages and landscapes. The optimum would be sea reservoirs built with the Tsunami-Flooding Barriers [11]. With visible installations for the water guns outside the reactor building, with watering exercises and with proper information, people can be assured that evacuation will not be required in the future, even in case of an accident.

If a long-lasting fire occurs as in Chernobyl, where the graphite moderator burnt and sent radioactive clouds very high so that contamination spread over large distances or in case of Fukushima, where the cloud left the reactor building and was carried by wind, intensive suction should be considered. **Figure 3** schematically shows the reactor building with attached large-diameter steel pipes which collect the cloud by a powerful ventilator of at least 5000 m3 per hour depending on tube diameter. A sprinkler system condenses the radioactive vapors and particles, and this contaminated water should then flow into the sea reservoir or into a basin. In case of Fukushima, this contaminated water should in the first phase have been transported by long pipes to the Kuroshio current where it is diluted. In the second phase, the gaps of 100 and 140 m between the existing seawalls/breakwaters could have been closed and water could have been pumped out to the basins where it could be collected and stored for later treatment. The intense spraying followed by the suction activity would have reduced the extended radioactive spreading and thus the evacuation requirements. Such suction systems could also be useful in case of accidents and fires in chemical factories and in oil refineries.

Reactor surrounding should always be covered by a thick concrete layer with a slope of 2–3° in the direction of the sea or the basin, so that all water is controlled and collected and the soil

In case of a such nuclear accident, there are two aspects which require immediate action:

**4.1. Missed chances to reduce the contamination level**

**March 11, 2011**

92 Environmental Risks

reactor engineer.

cannot be contaminated.

After the initial weeks following the accident, large amounts of cooling water had been pumped into the reactors, for example, 300 metric tons per day, which initially was further diluted with 400 m3 groundwater. Despite large efforts taken to reduce the influx of groundwater, it could not be stopped. Half of the water returning from reactor cooling was filtered and partially decontaminated and returned for cooling, and the other half of 200 m3 was collected daily in large storage tanks in the plant surroundings for later treatment. A fraction of this tank collection is shown in **Figure 4**.

Decontamination of water was problematic. Equipment from France, USA and Japan had been applied using reverse osmosis, adsorption by zeolites or evaporation of salt water.

**Figure 4.** Fraction of tanks with >300,000 m3 contaminated water at Fukushima power plant.

Problems have been errors in handling of valves, repeated leakages of connections and pipes and stopped pumps which could not be re-activated. Reference [15] gives some details of the dramatic water contamination problems. From outside it looks like small-scale attempts to solve large-scale problems.

With the existence of the three seawalls in front of the coast of Fukushima plants, there is the possibility to connect the ends of these seawalls by new walls of 100 and 140 m length to form three basins as shown in **Figure 5**.

To construct these barriers by conventional technology with rubble mound foundations and top caissons [8] or to build concrete walls would be a lengthy process and not provide highest safety. Recently, two methods have been developed which allow efficient construction of submerged barriers at reduced costs [11, 16]. In a first step, deep "beds" are dredged into the bottom of the sea with the depth depending on the sea ground (rocks, gravel, sand, mud). In the double-pontoon technology, two separated pontoons start from a ramp road at the coast and allow to move trucks. The first truck inserts a stainless steel (316L, 316LN, 1.4429) fence outside the pontoons into the sea, for instance, stable fence of Geobrugg, Romanshorn, Switzerland. The next truck inserts alternating rocks and concrete in the gap between the pontoons into the sea. Distance holders allow to erect a stable vertical wall of 6 –20 m width. These central pontoons hang on steel beams between assisting pontoons in order to carry the heavy weights. The second technology uses long tall cylinders of more than 100 m length fabricated in the harbor and floated to the site where they are inserted into the sea bed and filled with rocks, sand, and so on. These walls named Tsunami-Flooding-Barriers (TFB) are vertical toward the sea and thus reflect the impulse waves of tsunami. They extend about 10 m above sea level and carry a service road on top which is protected against storm waves by replaceable surge stoppers (parapets) [11].

Navier–Stokes Computational Fluid Dynamics CFD model [19] allowed a more accurate simulation of the fluid–structure interaction. The high efficiency of the TFB to reflect the tsunami impulse waves and the storm-wave reflection of the surge stopper (parapet) is confirmed.

Experiences from the Fukushima Disaster http://dx.doi.org/10.5772/intechopen.77726 95

The TFB concept could find wide application as it protects coastal cities and industries, but also beaches against tsunami and against flooding from tropical storms like hurricanes and typhoons. Also, flora and fauna could be saved in case of an oil-spill. In the past 20 years, these natural

Furthermore, the loading onto the vertical walls has been estimated [17].

**Figure 5.** De-contamination of water and release to the sea, schematic top view.

Hydrodynamic modeling [17] of the action of TFB barriers by coupling the far-field depthaveraged Boussinesq-type model pCOULWAVE of Lynett et al. [18] with a near-field

**Figure 5.** De-contamination of water and release to the sea, schematic top view.

Problems have been errors in handling of valves, repeated leakages of connections and pipes and stopped pumps which could not be re-activated. Reference [15] gives some details of the dramatic water contamination problems. From outside it looks like small-scale attempts to

**Figure 4.** Fraction of tanks with >300,000 m3 contaminated water at Fukushima power plant.

With the existence of the three seawalls in front of the coast of Fukushima plants, there is the possibility to connect the ends of these seawalls by new walls of 100 and 140 m length to form

To construct these barriers by conventional technology with rubble mound foundations and top caissons [8] or to build concrete walls would be a lengthy process and not provide highest safety. Recently, two methods have been developed which allow efficient construction of submerged barriers at reduced costs [11, 16]. In a first step, deep "beds" are dredged into the bottom of the sea with the depth depending on the sea ground (rocks, gravel, sand, mud). In the double-pontoon technology, two separated pontoons start from a ramp road at the coast and allow to move trucks. The first truck inserts a stainless steel (316L, 316LN, 1.4429) fence outside the pontoons into the sea, for instance, stable fence of Geobrugg, Romanshorn, Switzerland. The next truck inserts alternating rocks and concrete in the gap between the pontoons into the sea. Distance holders allow to erect a stable vertical wall of 6 –20 m width. These central pontoons hang on steel beams between assisting pontoons in order to carry the heavy weights. The second technology uses long tall cylinders of more than 100 m length fabricated in the harbor and floated to the site where they are inserted into the sea bed and filled with rocks, sand, and so on. These walls named Tsunami-Flooding-Barriers (TFB) are vertical toward the sea and thus reflect the impulse waves of tsunami. They extend about 10 m above sea level and carry a service road on top which is protected against storm waves

Hydrodynamic modeling [17] of the action of TFB barriers by coupling the far-field depthaveraged Boussinesq-type model pCOULWAVE of Lynett et al. [18] with a near-field

solve large-scale problems.

94 Environmental Risks

three basins as shown in **Figure 5**.

by replaceable surge stoppers (parapets) [11].

Navier–Stokes Computational Fluid Dynamics CFD model [19] allowed a more accurate simulation of the fluid–structure interaction. The high efficiency of the TFB to reflect the tsunami impulse waves and the storm-wave reflection of the surge stopper (parapet) is confirmed. Furthermore, the loading onto the vertical walls has been estimated [17].

The TFB concept could find wide application as it protects coastal cities and industries, but also beaches against tsunami and against flooding from tropical storms like hurricanes and typhoons. Also, flora and fauna could be saved in case of an oil-spill. In the past 20 years, these natural catastrophes have caused a quarter of a million fatalities and damages exceeding 500 billion US dollars mainly in Japan, Indonesia, Malaysia, Philippines, Sri Lanka, India and at the east coast of USA. In Japan, the TFB would have prevented in 2011 the 19,000 tsunami fatalities and 300 billion US dollars damages with destroyed houses and, of course, it would have prevented the Fukushima catastrophe. For the countries with risk of storm and tsunami flooding, such a large project would stimulate the building, transport and steel industries and would occupy thousands of workers and thus would have a significant impact on the economic development.

new land. The rubble caused by the reactor explosions, the drums with sludge from the decontamination process, all the plastic bags with collected contaminated soil and all contaminated material presently stored in Interim Storage Facilities will be transported to this dump. Finally, the debris from scrapping the destroyed reactors 1–4 could be deposited in these basins. The concrete debris could partially be milled and used for new concrete buildings.

The schematic cross-section view (**Figure 6**) of this "Fukushima dump" shows the original reactor before dismantling as well as the dump in the basin which is protected against flooding with the Tsunami-Flooding-Barrier. In view of keeping radiation and the elevated temperature, the molten fuel rods, after sufficient cooling in 30–80 years, should be enclosed in tubes of a metal which is relatively stable against oxidation at ambient oxygen pressure and temperature and limited humidity. Theoretically, the best materials for encapsulation would be the noble metals silver, gold and platinum but their high value would make them too attractive and thus cause a risk for the storage site for radioactive waste. **Figure 7** shows the temperature dependence of the thermodynamic stability of oxides of metals which could be applied as container for radioactive material. This Ellingham-type diagram [20], extended

Practical values for temperature can be obtained by a straight line passing from one of the three points (O, H, C) on the left margin to the oxygen partial pressure or the gas ratios on the scales on the right side of the diagram and hitting the stability line of the specific metal. Ironnickel-chromium alloys (stainless steel) and lead could be considered, and copper is foreseen

Depending on the shape of molten fuel rods within their surrounding they could be cut to pieces and enclosed in capsules or in thin tubes of one of the suitable metals and then sealed. In any case, the fuel-rod-material should be safely stored in a site from which it can be recov-

**Figure 6.** Storage of the rubble of the dismantled reactor building and of the collected contaminated soil in basin I which before had been emptied and covered with a thick concrete layer. After sufficient cooling the fused fuel is encapsulated and inserted into the cavity. Finally, with concrete cover on top new land is generated. The Tsunami-Flooding-Barrier

protects against future tsunami and against flooding from typhoon. (Schematic cross section).

ered by future generations to use the significant energy remaining in the fuel rods.

O gas ratios by Richardson and Jeffes [21], is discussed in [22].

Experiences from the Fukushima Disaster http://dx.doi.org/10.5772/intechopen.77726 97

for CO–CO<sup>2</sup>

and for H2

–H<sup>2</sup>

for enclosing radioactive material in Sweden.

Now Japan started a large project to build tall concrete walls, with height up to 14 m and width up to 46 m, along the coast of Honshu. The estimated costs are higher than building the TFB walls submerged in the sea at large distances from the coast, thereby not disturbing the view of the ocean for coastal citizens and for tourists. Fishermen would keep access to the sea. The population has formed a large resistance against the Japanese great wall of which only partial protection can be expected in case of a large tsunami which on March 11, 2011, had a reported maximum height of 38 m. The 500 km great wall along Honshu coast would consume 23 million m2 land area plus land surface for the required construction and service roads.

The water from the three basins (shown in **Figure 5**) is pumped out before their bottom is covered with a thick concrete layer. Contaminated water from reactor cooling, from the collecting point of the sloped concrete ground and from the storage tanks flows into basin I. After passing through the first decontamination stage, it enters basin II and then through the next decontamination step to basin III. After checking the low residual radioactivity from cesium-134, cesium-137 and Sr-90, the remaining radioactivity will be from tritium. This has a short half-life time of 12.3 years and anyhow occurs naturally in seawater, formed by cosmic rays, in extremely low concentrations of hydrogen(10−18). Therefore, there is no risk if this tritium-containing water of basin III is transported through long pipes into the Kuroshio current near the Japan trench which has a depth of 10 km. The short half-life time and the dilution effect will prevent the detection of tritium supply from Fukushima.

In view of the large quantity of contaminated water in the 1000 m3 tanks, a pre-decontamination step could be to introduce by stirring an isotope-adsorbing agent (e.g. zeolite) into the tank and letting it settle by gravity for sufficient time so that the deposit mud on the tank bottom can be sucked by slowly sweeping long tubes and then compacted by a drying process. An alternative could be salting-out and precipitate cesium-137 compounds. This would reduce the contamination level of the collected water and facilitate the final treatment.

#### **4.3. Storage of radioactive waste**

The storage of radioactive waste consisting of used fuel rods, of cut pieces of the reactor chambers, of rubble from the reactor foundation and building and from contaminated soil collected from the reactor surrounding is a technological challenge but mainly a political problem. Therefore, a site near the reactor ruins could find minimum resistance from the public. Large amounts of concentrated radioactive waste were collected and transported to the temporary storage facility.

After solving the water problem, the three sea basins with the thick concrete bottom are pumped empty and used as a dump for radioactive waste with the final goal of reclaiming new land. The rubble caused by the reactor explosions, the drums with sludge from the decontamination process, all the plastic bags with collected contaminated soil and all contaminated material presently stored in Interim Storage Facilities will be transported to this dump. Finally, the debris from scrapping the destroyed reactors 1–4 could be deposited in these basins. The concrete debris could partially be milled and used for new concrete buildings.

catastrophes have caused a quarter of a million fatalities and damages exceeding 500 billion US dollars mainly in Japan, Indonesia, Malaysia, Philippines, Sri Lanka, India and at the east coast of USA. In Japan, the TFB would have prevented in 2011 the 19,000 tsunami fatalities and 300 billion US dollars damages with destroyed houses and, of course, it would have prevented the Fukushima catastrophe. For the countries with risk of storm and tsunami flooding, such a large project would stimulate the building, transport and steel industries and would occupy thousands of workers and thus would have a significant impact on the economic development. Now Japan started a large project to build tall concrete walls, with height up to 14 m and width up to 46 m, along the coast of Honshu. The estimated costs are higher than building the TFB walls submerged in the sea at large distances from the coast, thereby not disturbing the view of the ocean for coastal citizens and for tourists. Fishermen would keep access to the sea. The population has formed a large resistance against the Japanese great wall of which only partial protection can be expected in case of a large tsunami which on March 11, 2011, had a reported maximum height of 38 m. The 500 km great wall along Honshu coast would consume

land area plus land surface for the required construction and service roads.

tanks, a pre-decontamination

The water from the three basins (shown in **Figure 5**) is pumped out before their bottom is covered with a thick concrete layer. Contaminated water from reactor cooling, from the collecting point of the sloped concrete ground and from the storage tanks flows into basin I. After passing through the first decontamination stage, it enters basin II and then through the next decontamination step to basin III. After checking the low residual radioactivity from cesium-134, cesium-137 and Sr-90, the remaining radioactivity will be from tritium. This has a short half-life time of 12.3 years and anyhow occurs naturally in seawater, formed by cosmic rays, in extremely low concentrations of hydrogen(10−18). Therefore, there is no risk if this tritium-containing water of basin III is transported through long pipes into the Kuroshio current near the Japan trench which has a depth of 10 km. The short half-life time and the dilution

step could be to introduce by stirring an isotope-adsorbing agent (e.g. zeolite) into the tank and letting it settle by gravity for sufficient time so that the deposit mud on the tank bottom can be sucked by slowly sweeping long tubes and then compacted by a drying process. An alternative could be salting-out and precipitate cesium-137 compounds. This would reduce

The storage of radioactive waste consisting of used fuel rods, of cut pieces of the reactor chambers, of rubble from the reactor foundation and building and from contaminated soil collected from the reactor surrounding is a technological challenge but mainly a political problem. Therefore, a site near the reactor ruins could find minimum resistance from the public. Large amounts of concentrated radioactive waste were collected and transported to the temporary

After solving the water problem, the three sea basins with the thick concrete bottom are pumped empty and used as a dump for radioactive waste with the final goal of reclaiming

effect will prevent the detection of tritium supply from Fukushima.

the contamination level of the collected water and facilitate the final treatment.

In view of the large quantity of contaminated water in the 1000 m3

**4.3. Storage of radioactive waste**

storage facility.

23 million m2

96 Environmental Risks

The schematic cross-section view (**Figure 6**) of this "Fukushima dump" shows the original reactor before dismantling as well as the dump in the basin which is protected against flooding with the Tsunami-Flooding-Barrier. In view of keeping radiation and the elevated temperature, the molten fuel rods, after sufficient cooling in 30–80 years, should be enclosed in tubes of a metal which is relatively stable against oxidation at ambient oxygen pressure and temperature and limited humidity. Theoretically, the best materials for encapsulation would be the noble metals silver, gold and platinum but their high value would make them too attractive and thus cause a risk for the storage site for radioactive waste. **Figure 7** shows the temperature dependence of the thermodynamic stability of oxides of metals which could be applied as container for radioactive material. This Ellingham-type diagram [20], extended for CO–CO<sup>2</sup> and for H2 –H<sup>2</sup> O gas ratios by Richardson and Jeffes [21], is discussed in [22]. Practical values for temperature can be obtained by a straight line passing from one of the three points (O, H, C) on the left margin to the oxygen partial pressure or the gas ratios on the scales on the right side of the diagram and hitting the stability line of the specific metal. Ironnickel-chromium alloys (stainless steel) and lead could be considered, and copper is foreseen for enclosing radioactive material in Sweden.

Depending on the shape of molten fuel rods within their surrounding they could be cut to pieces and enclosed in capsules or in thin tubes of one of the suitable metals and then sealed. In any case, the fuel-rod-material should be safely stored in a site from which it can be recovered by future generations to use the significant energy remaining in the fuel rods.

**Figure 6.** Storage of the rubble of the dismantled reactor building and of the collected contaminated soil in basin I which before had been emptied and covered with a thick concrete layer. After sufficient cooling the fused fuel is encapsulated and inserted into the cavity. Finally, with concrete cover on top new land is generated. The Tsunami-Flooding-Barrier protects against future tsunami and against flooding from typhoon. (Schematic cross section).

The original sea walls with seaside slopes will be complemented with Tsunami-Flooding-Barriers [11, 16] with the vertical wall on the seaside so that future tsunami and typhoons cannot harm the deposit development. Protection against heavy rain by a cover and against storm waves by a large floating fence in front of the TFB barriers [23] will prevent disturbance of the dump activities. With proper planning the sequence and the locality of the radioactive waste, the final radioactivity on top of the dump will not be higher than the natural value in

Experiences from the Fukushima Disaster http://dx.doi.org/10.5772/intechopen.77726 99

With this procedure the total costs for dismantling the reactors, for decontamination, for interim storage and for final storage of about 100 billion US dollars can be significantly

The Fukushima accident (and also the former Three-Mile-Island and Chernobyl catastrophes) has demonstrated that no engineer and manager with wide experiences and deciding power have been on site. In the case of Fukushima, urgent actions for very intense water spraying the fire and the cloud, for suction of the cloud, for manually opening the valve of the passive cooling system and for covering the ground with a thick concrete layer with slope of 2–3° depended on decisions of the owner's headquarters in Tokyo. This was concentrated on the internal problems of the reactors, on political and publicity pressure and anyhow was under enormous stress and was not aware of the consequences for the local population and of the following national and international consequences. The experiences from the Three-Mile-

Competent reactor engineers should be educated who learn, besides nuclear technology, about all possible chemical reactions, corrosion and electro-corrosion, properties of the involved materials, failure of materials and components, aero-and hydrodynamics, meteorol-

Another question is about the possibility for emergency interruption of nuclear fission by cadmium-indium alloys inside thin silver tubes and boron carbide/boron nitride/boron oxide composite tubes, whether such tubes can be inserted into Type-II generators until the safe generation III/III+ and IV reactors with a four-fold redundancy of emergency equipment will

It has become clear that the Fukushima accident could have been prevented if in the planning stage the worst-case scenario would have been considered by the plant owner and by the responsible ministry. Even after the accident caused by the unexpected tsunami, the collateral damages could have been mitigated if a competent foresighted management had timely initiated the described procedures. An international emergency team of top engineers with multidisciplinary and industry experience could assist worldwide in case of heavy nuclear,

Island accident and the recommendations have been summarized in Ref. [24].

Japan.

reduced.

ogy, and so on.-.

be developed.

chemical, fire and other catastrophes.

**5. Conclusions and outlook**

**Figure 7.** Standard free energy of formation of metal oxides as a function of temperature.

These tubes and capsules are then introduced through an opening shown in **Figure 6** into a barium-concrete chamber prepared below the bottom of the dump. Leakage to the ocean will be excluded when the material with highest radioactivity is stored in basin I and basins II and III also have been emptied, provided with a thick concrete layer, and used as dry dump for less-contaminated waste.

The original sea walls with seaside slopes will be complemented with Tsunami-Flooding-Barriers [11, 16] with the vertical wall on the seaside so that future tsunami and typhoons cannot harm the deposit development. Protection against heavy rain by a cover and against storm waves by a large floating fence in front of the TFB barriers [23] will prevent disturbance of the dump activities. With proper planning the sequence and the locality of the radioactive waste, the final radioactivity on top of the dump will not be higher than the natural value in Japan.

With this procedure the total costs for dismantling the reactors, for decontamination, for interim storage and for final storage of about 100 billion US dollars can be significantly reduced.
