Fukushima Daiichi Studies and Publications from JNES – List of Analysis Documents Released October 2011

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http://www.jnes.go.jp/jyohou/kouhyo/…published.html The analysis documents released by JNES

http://www.jnes.go.jp/content/000119660.pdf Analysis of criticality safety of metal casks: in order to find out how the humidity inside casks can bring criticality, an analysis was made based on constant assumptions. It was found that criticality is not reached even if there is humidity, etc.

http://www.jnes.go.jp/content/000119661.pdf Causes of 15 March unit 4 explosion/blaze: At unit 4 it is possible that fuel pool water declined, spent fuel was exposed, hydrogen was produced from a reaction between steam and fuel cladding tubes and exploded. Adding water in pools and cooling is also needed at other units.

http://www.jnes.go.jp/content/000119662.pdf Radioactivity of the spent fuel pool releases: Two sets of hypothesis were used to calculate conservative estimates of the spent fuel pool releases.

http://www.jnes.go.jp/content/000119663.pdf What happens if the present water injection at units 1,2,3 stops: Analysis of the time taken for fuel exposure, RPV damage, PCV damage under a set of hypothesis such as being 144 hours after reactor shutdown.

http://www.jnes.go.jp/content/000119664.pdf Reactivity effects of injecting seawater into spent fuel pools: Even if only seawater is injected, 600 ppm borated water is effective, as it can reduce reactivity by about one half.

http://www.jnes.go.jp/content/000119665.pdf Reactivity control by injecting boron or seawater in storage pools: a major criticality control effect is obtained when seawater or boron is injected in spent fuel pools.

http://www.jnes.go.jp/content/000119666.pdf INES level based on fuel damage proportion: Inferring from the fuel damage proportion, INES level 5 is estimated. An estimate of the proportion of Zr reaction needed for hydrogen explosion is found for each unit.

http://www.jnes.go.jp/content/000119667.pdf Whether criticality can occur with the mist produced at unit 4 SFP. If the racks are lost, criticality is possible.

http://www.jnes.go.jp/content/000119668.pdf Boric acid quantities needed for recriticality prevention: Using the most severe hypothesis, the quantity of boric acid needed to maintain subcriticality is 18.3 tons.

http://www.jnes.go.jp/content/000119669.pdf Risk assessment of cooling methods at units 1,2,3: Assessment of hydrogen explosion risk, steam explosion risk, salt damage risk encountered in plant cooling operations.

http://www.jnes.go.jp/content/000119671.pdf Temperature rise in spent fuel pools (water-zirconium reaction): temperature behavior of fuel in steam atmosphere when water level declines in the perspective of fuel meltdown.

http://www.jnes.go.jp/content/000119672.pdf Quantities of salt deposits in unit 2: assesment of salt deposits caused by seawater injections. As the salt concentration for saturation is not reached, there is no salt deposit.

http://www.jnes.go.jp/content/000119673.pdf Estimate of Fukushima Daiichi radiation releases. Based on remote monitoring values, the releases are reverse calculated using a simple model.

http://www.jnes.go.jp/content/000119683.pdf Unit 1 leakage area estimate (about the conditions on the morning of 12 March before the wet well vent and hydrogen explosion): As the reactor water level is declining, because the RPV pressure is not increasing, it is thought that all the generated steam is leaking and the leak’s area is estimated.

http://www.jnes.go.jp/content/000119682.pdf Quantities of salt deposits in unit 2 (revised version): Estimate of the salt deposit quantities resulting of seawater injection. With a 410 l/min water injection rate, it is thought that there is enough margin, and salt deposits are not created.

http://www.jnes.go.jp/content/000119681.pdf Estimate of radiation from drywell vent pipe and temporary pit at units 1,2,3: Estimates of dose rates from temporary pit, from drywell venting pipe, and in the flowing water.

http://www.jnes.go.jp/content/000119681.pdf CCI study: Judging from the situation at the plant until now, the melted fuel has fallen little by little. The heat flux of crust dryout exceeds decay heat, so that the solidification of melted objects occurs.

http://www.jnes.go.jp/content/000119679.pdf study of criticality of unit 4 fuel pool: assessment of criticality after the fuel assemblies are damaged, the fuel rod pellets fall to the bottom and are spread or form compact bodies. In a very conservative assessment, criticality is possible, but with a realistic credit (U235x07), even if the pellets fall down criticality does not occur.

http://www.jnes.go.jp/content/000119678.pdf Answer about the Evacuation prepared zone (EPZ) if the release quantity is changed from one to three reactor cores. Taking into account the external radiation dose of the whole body, the EPZ is extended by about 19 km. If the thyroid equivalent dose of children is taken into account, the EPZ is extented by about 16 km.

http://www.jnes.go.jp/content/000119677.pdf conversion of unit 3 PCV releases (permeability). The release (permeability) is calculated with a simple Bernouilli equation, without taking critical flow into account.

http://www.jnes.go.jp/content/000119676.pdf Answer about the Evacuation prepared zone (EPZ) if the release quantity is changed from one reactor core to two or two and a half reactor cores. With two and a half reactor cores, taking into account the external exposure of the whole body, the EPZ is extended by 15 km. Taking into account children equivalent thyroid doses, it is extended by 12 km. With 2 reactor cores the EPZ is extended respectively by 11 and 8 km.

http://www.jnes.go.jp/content/000119675.pdf Answer about the concentrations of core materials in the suppression pool (boron, cesium). concentrations of core materials in the suppression pool (boron, cesium) in a scenario of damage by excess of temperature.

http://www.jnes.go.jp/content/000119674.pdf possibility of PCV damage caused by hydrogen explosion. Even if explosion occurs, the design maximum pressure of reactor vessel is high and the resistance to pressure is sufficient. A break of the top part of the reactor vessel causing PCV damage is not thought to be possible.

http://www.jnes.go.jp/content/000119684.pdf radiation releases caused by unit 1 venting. If venting is performed in the future, the added release into the atmosphere is thought to be small.

http://www.jnes.go.jp/content/000119685.pdf assessment of hydrogen and oxygen concentrations at unit 1: Using conservative hypothesis, oxygen concentration is 2.1% and the combustion limit of 7% in steam atmosphere is not exceeded.

http://www.jnes.go.jp/content/000119686.pdf core-concrete reaction (MCCI) possibility and consequences: assessment of progression possibility of core-concrete reaction (MCCI) and concrete erosion consequences.

http://www.jnes.go.jp/content/000119687.pdf Answer to NRC recommend. (MELCOR analysis results in case of loss of all AC power): Past results of MELCOR analysis in case of loss of all AC power). Estimates of the time it takes for RPV and PCV damage in cas of loss of all AC power.

http://www.jnes.go.jp/content/000119688.pdf confirmation of the presence or absence of core recriticality: Study of the causes of neutron measurement data above the detection level revealed at Fukushima Daiichi monitoring points.

http://www.jnes.go.jp/content/000119689.pdf About the neutron leak at unit 4 storing pool: From 14 March to 15 March, neutron measurement data above detection level have been revealed at the Fukushima Daiichi monitoring points. Study of the causes of these measurements.

http://www.jnes.go.jp/content/000119690.pdf Comment about Tepco document “countermeasures against leaks during the storage of highy radioactive water in the concentrated waste tratment facility buildings”. Comment about Tepco’s assessment of cesium diffusion. That assessment is nearly valid.

http://www.jnes.go.jp/content/000119691.pdf Forecast of radiation doses in each area and at at each time, based on an analysis of the real measured values. In order to understand radiation exposure consequences before a monitoring system is secured, estimates are given for each area from 14 March to 18 March.

http://www.jnes.go.jp/content/000119692.pdf recriticality prevention at unit 1 during the shift to closed loop cooling: Based on the survey results obtained after the Three Mile Island accident, recriticality is analysed assuming the debris are in a conic shape and surrounded by borated water.

http://www.jnes.go.jp/content/000119693.pdf forecast of radioactive substances released from Fukushima Daiichi: calculated estimate of fission products from unit 1. Presentation of needed data for fission products in other units.

http://www.jnes.go.jp/content/000119694.pdf quantity of gaseous iodine releases at Fukushima Daiichi. Calculation using reference books of gaseous iodine releases from unit 1 polluted water to the gaseous part of the building.

http://www.jnes.go.jp/content/000119695.pdf About the validity of the operator’s assessment of the improvement of working environment at unit 2: confirmation of the validity of the operator’s assessment, using a calculation of the radioactive substances’ concentrations in the air in the plant premises.

http://www.jnes.go.jp/content/000119699.pdf Possibility of hydrogen explosions at units 2 and 3. Study of possibility of hydrogen explosion occurrence if reactor cooling is not carried out, and if reactor cooling is carried out.

http://www.jnes.go.jp/content/000119698.pdf Time it takes for meltdown at unit 4 fuel pool: Calculation of the time taken until meltdown, for the fuel with the highest decay heat, based on real heat insulation conditions.

http://www.jnes.go.jp/content/000119697.pdf Study of earthquake safety of unit 4 reactor building in the present conditions. Study intended at confirming the validity of the operator’s assessment of earthquake safety in the present conditions of the building, assuming the greatest aftershock of the present earthquake.

http://www.jnes.go.jp/content/000119696.pdf Study of earthquake safety of unit 3 reactor building in the present conditions. Study intended at confirming the validity of the operator’s assessment of earthquake safety in the present conditions of the building, assuming the greatest aftershock of the present earthquake.

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