Blast Data From Fukushima -- To Shred 18" Reinforced Concrete Walls, C4 Explosive Not Enough, Hydrogen -- No Way

Certainly in calculating damage from an explosive blast, we would need to consider not just peak pressure achieved, but also the "impulse" the rate of pressure change.    From C4 or TNT, peak pressures are achieved very quickly, say 1 to 3 milliseconds.

I used a study by the US Military on an 18" reinforced concrete wall, in which they ran explosive tests with documentation.

Their bombs were roughly 220 lbs of explosive material, placed 7 feet away from a wall.

Basically, even after 5 large bombs were set off, the damage seen was still less than the damage seen at Fukushima.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwjv_vX53d_MAhXEx4MKHbJ9A1AQFggmMAE&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA171947&usg=AFQjCNGcen5-USChXBXuEuGlf7jOQUvKSw&sig2=iW2KJxnsEMn9HHd_w6eZ1w&cad=rja

Fukushima 3 and 4 were NOT hydrogen explosions, they were a type of nuclear explosion. 

Hydrogen is good at making a very high temperature blast, but not a very high energy blast.

The flame from burning hydrogen has a very high heat content — its flame temperature is 3,700 degrees Fahrenheit. Hydrogen burns with an almost invisible flame, converting all energy into heat energy

 

from the reference above

Here is the RE, Relative Effectiveness of various explosive materials.

https://en.wikipedia.org/wiki/Relative_effectiveness_factor


Here is another course of blast research material, less technical, more for management types

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwjv_vX53d_MAhXEx4MKHbJ9A1AQFgg4MAM&url=http%3A%2F%2Fwww.fema.gov%2Fmedia-library-data%2F20130726-1455-20490-7465%2Ffema426_ch4.pdf&usg=AFQjCNE5LiQVJvzAyNhQyc8jzGmdoXkPDg&sig2=NCHEk752RWGSYNikj4NT3Q&cad=rja

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Now some data on the explosive power of hydrogen

 stock here, calculations by the NRC based on a reactor building full of hydrogen.

An equivalent amount of TNT is calculated, it is roughly equal to 61 bombs of the 220 lbs size the US Military used in trying to blow up a 18" reinforced concrete wall.

The damages from those 220lb bombs was minor in relation to the damages suffered at Fukushima.

 Source--
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&cad=rja&uact=8&ved=0ahUKEwjGusn479_MAhVn_4MKHYxDAh84ChAWCDAwAw&url=http%3A%2F%2Fwww.nrc.gov%2Fdocs%2FML0906%2FML090630278.pdf&usg=AFQjCNFecskX03KfmbrKV4wTWbV9ABdgBA&sig2=655sQvBx2tcQ6JMHODetow&bvm=bv.122129774,d.amc

Add caption

 
And additional support for the "Hell No Hydrogen Explosion"
http://agreenroad.blogspot.com/2016/05/how-and-why-hydrogen-explosions-could.html

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http://www.eng-tips.com/viewthread.cfm?qid=276651

MrShaff (Military)

(OP)

14 Jul 10 09:59

Hi

I am a physical security consultant, i have a client who is concerned about a hydrogen / air explosion in his factory. I would like to know the pressures that could be attained using the following scenario

room size - 40m3
explosive - equivalent to 5kg TNT (is that possible for calculations)

what would pressure and impulse be on the walls of the room?

  

Compositepro (Chemical) 14 Jul 10 11:39

I have not done the calculation for hydrogen but for most hydrocarbons the maximum adiabatic combustion pressure is very close to 150 psi, or 10 times the initial pressure. This assumes all of the chemical energy goes into heating and expanding the mixture. The pressure rise is mainly limited by the available oxygen in air. I'm not sure if the shock wave pressure would go much above that. It won't be less than that.

ajs1972 (Chemical) 14 Jul 10 14:35

According to the volume of the room and UEL and LEL of hydrogen, the volume released of hydrogen that will cause an explosion will be between 2.08 and 39 kilograms and with an overpressure wave of 8.0 psi the buiding will be completely destroyed.

Overpressure (psi)        Expected Damage
   0.50-1.0                    Windows usually shattered.
   1.0-8.0                      Range for slight to serious injuries from flying glass and other missiles.
   2.0                             Partial collapse of walls and roofs of houses.

   2.4-12.2                    Range for 1-90% eardrum rupture among exposed populations.
   5.0                             Wooden utility poles snapped.
   5.0-7.0                       Nearly complete destruction of houses.
   7.0                             Loaded train cars overturned.
   10.0                           Probable total building destruction.
   14.5-29.0                   Range for 1-99% fatalities among exposed populations due to direct blast effects.

ajs1972 (Chemical) 14 Jul 10 15:02

With the values of UEL and LEL you will achieve more than 5 kilograms of TNT. An explosion in LEL value, the room will be destroyed.

StoneCold (Chemical) 15 Jul 10 13:40

ajs1972   How did you figure out the pressure wave of 8.0 psi?

Regards
StoneCold

ajs1972 (Chemical) 15 Jul 10 21:59

Hello StoneCold:

We have a 40 m3 room= 1.3 kg/m3 (density of air)*40 m3=52 kg of air. The LEL of hydrogen is 40000 ppm (weight)=0.04*52=2.08 kg. of hydrogen in leaks will reach the LEL.

The combustion heat of hydrogen is 33 859 kcal/kg, so 2.08 kg will produce 70426.72 kcal.

The combustion heat of TNT is 1080 kcal, so 2.08 kg of hydrogen are equal to 65.21 kg of TNT and 1 kg of TNT produces 0.73 m3 of gas, then 2.08 kg of hydrogen will produce 47.6 m3 of gas.

In a room of 40 m3, the pressure will increase by double, so the wave pressure will be 15 psi.

But if you review the table of wave overpressures, is necessary only 8 psi to destroy the building.

Compositepro (Chemical) 16 Jul 10 14:16

AJS I've checked very little of your math, but one mistake you make is that the combustion products are not at room temperature, they will be at thousands of degrees.
The peak pressures in a high explosive detonations are on the order of a million psi (at zero distance). As I said earlier, the peak pressure in a fuel-air deflagration is about 150 psi.  

ajs1972 (Chemical) 17 Jul 10 00:34

Hello Compositero:

You are right, a deflagration will produce, in a closed system, a maximum of 10 times the initial pressure.

Like you say a peak or maximum pressure could be 150 psi in atmospheric initial conditions. I said, overpressure waves 150 psi or 15 psi, twice are dangerous.

According to EPA tables, from 8 psi and more, the damages will be catastrophic.

Regards.

Shoefly (Chemical) 16 Nov 10 17:39

ajs1972
Careful!  Your concepts are flawed.

The use of ppm in the context of gases means parts per million - a concentration by volume - not a concentration by weight.

40,000ppm = 4%.

4% of a 40m3 volume of gas air/hydrogen mixture = 1.6m3 of hydrogen.

1.6m3 x 0.08375kg/m3 (mass of H2 at NTP) = 0.134kg of H2

Also, there is a difference in the lower flammable level and lower explosive level (LEL) for hydrogen.  A hydrogen air mixture explosion is most powerful at a stoichiometric mixture ~30% H2.
 

hacksaw (Mechanical) 21 Nov 10 09:59

Hardly a proper forum for such a calculation especially without a complete set of drawings describing the building, leak sources and ventilation methods.

my own limited experience is that hydrogen generally goes off as a burning process (significant and distructive in its own right) and is difficult to get it to detonate except in very special circumstances.

you really need a specialist to answer you questions, good luck