Recent presentations of the Admin on the severe accidents in TMI, Chernobyl and Fukushima.
Recent presentations of the Admin on German Nuclear Rules and Regulations.
The TEPCO accident report reveals the failure of the emergency measure "mobile injection by fire trucks". The admin has provided an English translation of the chapter on the role of the fire trucks from the TEPCO accident report. Click here.
New: Google presents street view type of pictures of tsunami damaged buidling. Very instructive for people interested in tsunami damage:
Strange understanding of the Defence-in-Depth principle in the new German "BMU Safety Criteria for Nuclear Power Plants - Revision D (2009)". Some comments by the admin, click here to read.
June, 10, 2013, Comments by the Admin on the Fukushima Clean-up Progress and the floods in Germany
Fukushima Clean-up Progress in Mai 2013
It is rather boring to read the information on the Fukushima progress since there is almost no progress. TEPCO has finished the steel frame for the unit 4 housing, it has build an improved cover over the unit 3 spend fuel pool and it is investigating the leaking of one (or more ?) underground tanks. It has published more than 200 follow-up reports on this (less important) leakage and also has published fotos and movies of low information value. Basically, there are no milestones that have been achieved and no serious incidents or accidents.
The amount of water stored in tanks is increasing as before and sooner or later TEPCO will apply for a license to dump the treated water into the sea. From a technical point of view this could be done without violating the radiation protection limits but it will not be accepted by the public. So the stragey of TEPCO is to continue with the storage in tanks until the public will accept the dumping.
TEPCO is dicussing various methods to keep the ground water from flowing into the basements, BUT in order to prevent the radioactive water in the basement which is leaking down from the containment, the groundwater level must be kept above the water level in the basement. There is no simple solution for this problem, all TEPCO may hope for is that it might decrease the inflow of groundwater but closing the major leaks in the basement walls at the price of a substatnial radiation load on the workers performing this job.
Flood in Germany
Germany is experiencing one of the biggest floods ever recorded. The public and the press are blaming the government for not having build dykes high enough for this flood. This is a very interesting phenomenon. The German public is heavily relying on desaster prevention and believing that engineered safety systems can be implemented that will cope with any situation possible.
This is similar to the situation in nuclear safety where the responsible persons fool the public by explaining that all risks can be avoided by enginered safety systems. This is not true for floods and not true for nuclear accidents. Up to a certain limit safety systems can limit the consequence of a flood or a malfunctining in a nuclear power plant. But there is this limit and this has to be accepted by the responsible persons and the public. If you build a dyke for floods of 8 m height, the next flood will have a height of 8,20 m and everything will be lost. Clearly any emergency preparedness has two component prevention and mitigation: For floods Germany needs more than dykes and people who put sand sacks on dykes to increase the height. Mitigation is also needed and this requires a certain flood preparedness: Buildings and installations which can be easily evacuated and cleaned after the flood, roads of approach along the dykes, and machinery to add big sand sacks to the dykes and not these folk festivals on the dykes with people putting 10 kg sacks to the dykes and politicians visiting these people shaking hands and hoping these scenes will make it to the evening news on tv.
The same is true for nuclear power plants: In addition to all the well designed safety systems, all equipment needed for mobile injection and movile power supply has to be available on-site and workers must be trained to execute the emergenca procedures. It is a severe mistake to think that because of the very low level of probability these mitigation measures are not necessary and therefore are not taken serious by the responsible persons.
Mai, 17, 2013, Cheapest Clean-up Solution for Unit 1
TEPCO has published a comparative analysis on the first step of unit 1 clean-up. We remember: Unit 1 has experienced a severe meltdown and was releasing a substantial amount of radioactivity in the months after the accident. In order to reduce the radioactive relase from unit 1 to an acceptable level TEPCO has constructed a huge tent structure over unit 1 called "building cover". TEPCO tried to filter the atmosphere under the tent which clearly is not leak tight. By this measure TEPCO achieved a reduction to 1/4 of the radioactive release before the installation of the tent.
This was and is insufficient. So TEPCO installed a venting system for the containment which proved more effective and achieved a reduction to 1/30 resulting in an overall reduction to 1%.
TEPCO has now analyzed three methods to remove the rubble from the fifth floor of unit 1.
- Clean-up under the tent cover
- Installation of a huge enclosing containment
- Removing the tent cover and clean up in the open air.
The last method is the cheapest and calculation show that it is feasible in view of the limits prescribed by radiation protection. So, TEPCO is persuing this solution. Quick and dirty!
Mai, 10, 2013, The great Fukushima Press Panic of Today: Mobile Toilet Burning?
Smoke from Near the North Side of Unit 6 at Fukushima Daiichi Nuclear Power Station
At around 9:25 AM today (May 10), a cooperative company worker found smoke coming out from near the mobile temporary toilet installed in the north side (outside) of Unit 6 at Fukushima Daiichi Nuclear Power Station.
The incident was reported to the fire department at 9:35 AM. (Since we judged that the incident was not a fire, site investigation was not done by the fire department.)
Upon site investigation, black smoke was found to be coming out from the exhaust stack of the engine generator installed in the mobile temporary toilet as the power supply for ventilation. The smoke was confirmed to have stopped coming out after suspending the generator.
As a result of site investigation, the smoke was identified to be the gas exhausted from the engine generator turning black due to oil loss via the piston ring of the engine generator. Thus, we have judged that this incident was not a fire.
Mai, 10, 2013, New Information of the Fukushima Clean-Up
TEPCO has published a new safety report on the technical details of the Fukushima Clean-Up Programme. This report can be found on the internet : http://www.tepco.co.jp/cc/press/betu13_j/images/130507j0102.pdf
Unfortunately it is available in Japanes only but Google Translate whelps to understand the msot important technical issues.
The report contains some new information on how TEPCO will implement the clean-up of the spent fuel pools (SPF). As has already been explained here before, TEPCO is erecting a large steel structure with plastic cover in form of a tent at the side of unit 4 which reaches over the SPF. This system will allow to control the atmosphere and filter out radioactive release in case something goes wrong while the spent fuel elements are placed into casquets and shipped to an on-site high radwaste storage. This costly structure is required since unit 4 rector building has experienced a substantial structural damage in the explosion and TEPCO does not want to put additional weight on the weakened structure.
For unit 2 and 3 TEPCO is planning to erect some kind of tent with steel ribs over the SPF allowing to control the atmosphere and filter out postulated radioactive release. Unit 1 already has a tent housing and the clean-up of the SPF will be carried out under this housing.
As shown in the figure, the planned system consists of a light-weight structure sitting on top od the fifth floor and inside this structure the hermetic area for air control can be found.
The figure shows the steel frame of the housing system.
TEPCO is planning to lower the ground water level by installing pump pits upstream of the reactor building in order to allow to lower the water level of the contaminated water in the basements. At the same tim TEPCO is trying to reduce the groud water ingress by closing the leaks in the basement walls. The report shows that most leaks are simple cracks in the concrette walls which can be closed by polyester coating or penetrations of piping and cables where the sealings are leaking which can be fixed by new sealings.
TEPCO is doing an adequate job in monitoring potential leaks by a system of monitoring pits at all critical locations as show inthe figure.
TEPCO is intending to store all radwaste on-site and is demonstating in the safety report that the storage is adequaste to meet the site conditions, e.g. earthquakes and tsunamis. This on-site storage is a sad story not be sustainable and the figure shows that sooner or later TEPCO will run out of space for additional tanks and storages.
April, 24, 2013, Unit 3 Spent Fuel Protective Cover
TEPCO has partially cleaned up the 5th floor of unit 3 and is installing a protecive cover over the spent fuel pool and the skimmer tanks. Thus, two years after the accident, TEPCO has managed to build a cover over the spent fuel pool and the fuel elements in the pool are longer remain standing unprotected in the open. TEPCO does not reveal if the new cover is leak tight and if there is some kind of air filtering installed or if the cover only keeps the rain, the storms, the birds and the mice away.
April, 19, 2013, The great drama of the leaking underground reservoirs - continued
TEPCO has published press release no. 74 today. Basically salt water has been found in only monitoring hole, which is an indicator of a leak. the data for this sample are:
Leakage detection hole (northeast) of the underground reservoir No.1
Chloride concentration: 1200ppm (Previously announced)
Iodine 131: Below the detection limit (Detection limit: 2.0×10-1Bq/cm3)
Cesium 134: Below the detection limit (Detection limit: 2.6×10-1Bq/cm3)
Cesium 137: Below the detection limit (Detection limit: 1.4×10-1Bq/cm3)
Antimony 125: 2.8×101Bq/cm3
Ruthenium 106: 2.3×100Bq/cm3
All beta: 3.5×104Bq/cm3
The samples from the other hole are negative with only a few ppm of chloride and very low level af radioactivity.
April, 15, 2013, The great drama of the leaking underground reservoirs - continued
TEPCO is still struggling with the water leak from the underground reservoirs. As of today TEPCO has published 59 press releases. The recent information contains some details on the underground reservoir structure
Basically these reservoirs are build like swimming pools made of concrete and not highly qualified, which is not necessary as the water has been decontaminated and is low level waste if it is has to be considered as radioactive waste at all. TEPCO has also published information on the location of the underground reservoirs.
April, 11, 2013, The great drama of the leaking underground reservoirs
TEPCO's poor accident management of the undergroud reservoir leakage has resulted in a real drama as the makeshift equipment for pumping the water from one tank to another tank stumbles from one failure to the next. The drama contains all kind of failure scenarios: the reservoir into which the water was planned to be pumped is also leaking, the pumps fail, the power supply fails, the newly installed piping systems leaks. As of today, TEPCO has published 35 press releases! The drama started on April 5th und is probably going on like this for the next days.
The picture is showing underground reservoirs with a monitoring man hole.
April, 10, 2013, Comment on the leakage
The press is reporting hysterically on the underground water leakage. There is no reason for this panic: Here are the facts: The water is leaking from the underground reservoirs no. 1 and no. 2. This has been detected by evaluating water sampüles taken from the control pits at the reservoir borders. The reservoirs contain sea water which has been decontaminated, that means the main contributor to radioactive contamination, cesium 134 and 137, has been extracted, cesium is below detection limit, only some contamination with beta sources has been detected. Iodine has dissapeared and no longer plays any role to the short half-life of a few days.
It should be kept in mind that the Fukushima site is highly contaminated due to the accident and it is not clear where the beta sources come from. TEPCO has not published any data of water samples taken from pits at some distance of the reservoirs.
April, 8, 2013, Underground reservoir is leaking
On April 3rd, TEPCO discovered elevated radiation levels in a water sample drawn at underground reservoir no. 2 The press reacted hysterically. The truth is: The radiation levels outside the underground reservoir no. 2 are extremely low. TEPCO is pumping the water from underground reservoir no. 2 into the other underground reservoirs. The table shows an overview over the available underground reservoirs.
March, 28, 2013, Application for more tanks to store radioactive water
We remember: Due to the high ground water level, ground water is flowing through cracks and leaks into the basements of the units 1- 4 and mixes with contaminated cooling water from the reactor vessels. Even after reprocessing this water has to be stored. Each day the amount of water is increased by about 400 m3. As of today TEPCO has stored about 240 000 m3 contaminated water in tank farms, many tanks with low radiation level water but also - as a consequence of treatment - some with very high levels. As TEPCO has no possibility to reduce the ground water ingress before the new system is in operation, TEPCO has applied for the license to build more tanks on site with a total of 700 000 m3 storage capacity.
The figure shows the new storage areas. The areas with no texture inside are the new areas. Basically, in the end TEPCO is going to store one cubic kilometer of contaminated water on site, which will pose a substantial problem to future generations as the tanks have only a limited life expectance.
March, 13, 2013, Unit 4 steel frame reaches 5th floor
For several months the housing structure for unit 4 is under construction. We remember: In the spent fuel pool of unit 4 about 1500 highly radioactive fuel elements are without any cover and separation from the environment. The safe removal is urgent. Safe removal requires som kind of housing to allow for control of the atmosphere inside the housing in case something goes wrong during removal. The radioactivity of the spent fuel elements is so high that they have to be underwater all the time for radiation shielding. Without water any person close to one of these elements recieves a lethal radiation dose immediately.
TEPCO is installing a giantic steel frame as a first step to build the housing. TEPCO is making good progress and the frame has reached the fith floor of unit 4. The picture gives an impession of the size of the steel frame structure.
March, 11, 2013, Unit 2 Blowdown Panel replaced by a new door.
One has to remember: in unit 2 it was not an explosion that has occurred during the accident but a pressure surge which has blown out one segment of the leak-tight reactor structure, that was designed as a rupture disk in case of overpressure.
Basically both the containment and the hermetic part of the reactor building (the one that includes the spent fuel pool have) have a controlled atmosphere and therefore have to be leak tight. The main difference is that only the containment has to be designed for substantial overpressure to withstand the pressure build up after a postulated pipe break. The hermetic part of the rector building cannot be overpressurized as no components are installed that in case of failure may cause overpressurization.
This shows how sophisticated the design of the early nuclear engineers was. Later nuclear engineers did not find it necessary to provide overpressure protection for containments or reactor buildings. Still today in spite of all the bad experience many cotainments have not been equipped with a controlled containment venting system.
Now, maybe to commemorate the second aniversary ?, TEPCO has placed as make-shift door into the opening and radioactivity can no longer escape from unit 2. The question remains: why not one and a half year earlier?
February, 28, 2013, Progress in Ground Water Control
One of the biggest Problem in disaster control is the large amount of ground water penetrating into the basements of the unit 1 - 4. This water is mixing with the radioactive cooling water and produces a large amount of contaminated water which after processing has to be stored in large tank farms on site. In order to prevent leackage from the basements to the environment, the water level in the basements has to be kept below the ground water level.
TEPCO has made a large progress in installing a ground water control system using pump wells to lower the ground water at the basements expecting that a lower ground water level will lead to a reduced water ingress into the basements.
The figure shows the pump wells.
The idea behind this is to lower the ground water level and at the same time lower the water level in the basements such that the ground water is still flowing into the basements and no contaminated water from the basements escapes into the ground water.
This is somewhat tricky due to the soil conditions below the units and the fact that ground water is pumped at some distance upstream the units. Until now, TEPCO is happy with the preliminary results. the level of contamination of the ground water pumped from the wells is so low that it can be dumped into the sea - no storage required.
In order to monitor the evolution of the ground water closely and to early detect potential flow of contamiated water from the basements, TEPCO is installing monitoring pits directly at the basements of the units.
February, 20, 2013, Emergency training exercise demonstrates: power and coolant supply can be restored within minutes
TEPCO has carried out a successful emergency training demonstrating that with a trained crew and adequate equipment, power and coolant supply can be restored within minutes. The pictures show the highlights from the training exercise:
Connecting the mobile power truck
Connecting the fire truck with a flexible fire hose to the injection line.
When these measures are carried out before the melt down there is no radioactive radiation in the places where the emergency personal is working, since no radioactivity has been released from the containment. Workers can move freely and perform all kind of work, It is only after the melt down and the release of a substantial amount of radioactivity that there is a restriction on the places where workers may go and the kind of work they can carry out.
If trained personal and adequate equipment had been available, the melt down at Fukushima could have been avoided easily. The German authorities and operators have refused and are still refusing to learn these lessons and to implement a similar emergency preparedness. It is unbelievable how stupid and short sighted the German reactions to the Fukushima accident are. Instead of putting a lid on the well they have put up warning signs!
The admin has said this many times before and he is re-iterating it again:
There is a limit to preventing severe acidents by pre-installed safety systems, even installing more safety systems will not make the nuclear power plant any safer by any standard. There is a limit to the success of preventing safety systems and beyond this limit mitigation by human accident management measures is required and these measures require trained personal and adequate equipment on-site.
February, 13, 2013, Recent aerial views from the accident site
In the Japanese press some aerial views taken from a helicopter have been published.
This picture shows an overall view of the four units
This picture shows the progess at unit 4, where the construction of a cover is underway.
These pictures show the large number of tanks that have been build for storing the decontaminated (low level contaminted) water and the blue high level sludge tanks.
The blue color means highly radioactive. Blue in Japan, yellow in Europe!
February, 4, 2013, TEPCO has published more than 1000 pictures taken in the first days of the accident
These pictures are a must for everyone interested in analyzing the accident. The pictures can be found at the internet-site
for download. Download with HTTWeb Side Copier works. Take about one day.
The admin has found one very interesting picture.
This picture shows the poor state of the unit 3 control room. This might have been a good control room in the 70ths but today it is definitely not state-of-the-art! This control room may be adequate to operate a reactor in normal states but the operaters are completely lost in case of a severe accident. In such a control room successful accident management cannot be achieved!
February, 1st, 2013, Workers radiation doses statistics
TEPCO has published data on the radiation doses Fukushima workers have received from march 2011 to december 2012:
How to interpret these data? USA regulations allow 50 mSv/year for professionals, EU and German regulations have a 20 mSv/year limit, but the regualtions say that a professional may receive not more than 100 mSv/year or a maximum of 50 mSv/year.
Applying these rules, workers with more than 50 mSv on their personal dosimeters should not be allowed to continue working on the Fukushima site. Contract workers are not the problem. Typically they are not specialized trained personal and can easily be replaced. The problem are the TEPCO workers and the data indicate that of the 3,628 TEPCO having worked on-site about 660 should not work on-site in the coming years. This means a substantial loss of trained man-power for TEPCO and also shows that on the long term TEPCO will have a problem to provide enough trained man-power for the clean-up.
As the admin has always pointed out these values are calculated values derived in a simplified approach and do not mean that some worker have suffered damage to their health. The approach to calculate the radiation doses and limits is a conservative approach and a pratical approach which is easy to do and also makes sure that the calulational limit garanties that no health damge was done to the worker. The data do not mean that hundreds of worker have serious health problems due to exceeding the limits.
TEPCO workers who have done work on-site
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