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Grenfell Tower and Browns Ferry

Dear Reader,

We have a problem in life, it is the problem of what is foreseeable. If I was to accidentally summon a giant acid spitting wasp this afternoon by stirring the drums of emulsion paint with a stick held in my right hand, while holding the roller in my left hand while wearing a red boilersuit and sunglasses. Then if this horrible wasp was to lay waste the whole of Vara in Sweden then while this combination of clothing and actions might have made the wasp appear it would be a simple but rather sad accident. An accident caused by complete chance that nobody could have predicted. The good folk of Vara would be unable to sue me for laying waste the whole town as I did not deliberately summon the wasp or do something reckless which made the wasp appear.

On the other hand if it was well known in Sweden that acid spitting giant wasps are attracted to the smell of emulsion paint, the color red and the reflection of light from sunglasses. Then this summoning of the wasp would from a legal point of view be at best the result of a reckless act or worse still the result of deliberate attempt to lay waste the neighborhood.

The question of “would it be reasonable to expect polyurethane foam to burn with great vigor if stuffed into a long tall vertical gap between a concrete building and a metal sheet ?” is one which some prior knowledge exists about. Lets for a moment ignore the other skyscrapers which had serious fires in their cladding, and cast our minds back to the 1970s. Back in the 1970s when I was a very small boy there was a nuclear power plant named Browns Ferry, what happened was a pair of workers were trying to check how good the sealing was with a candle flame. They managed to set fire to the foamed plastic, this fire then spread from the cable room into into the reactor buidling. The fire damaged electrical cables. A short NRC report can be seen on the event here. A nuclear sector trade magazine article on the fire can be read here.

The sealing material used was very combustible, it was a polyurethane foam which was ignited by the candle flame, at the time of testing it lacked the flame retardant coating. Now for those of you who have never set foot in a nuclear site, there is an air pressure issue which we need to know about. It is normal for the air pressure in a contaminated area to be lower than the outside world. I was once standing a few meters from someone who was doing a building modification, the person drilled a hole through a wall. On one side of the wall was a non radioactive area and on the other side of the special wall was a radioactive area. As soon as the hole was made I could hear the air whistling through the hole. The new cables were pushed through the hole and the hole was then sealed up with a sealing substance.

The idea is that if a leak occurs then it is better for clean air to leak into a radioactive area rather than radioactive air to leak into clean area. At Browns Ferry this sucked the flame from the cable room into the ducts taking the cables into the two reactors. I reason that also at Grenfell that a draught would have existed. If a flame exists inside a vertical tube which is open at both the top and the bottom then the warmth of the flame will heat up the air in the tube.

The air will expand and the density of the air is then lower, this will make the air rise up the tube sucking in more air at the bottom. This updraft of air will supply more oxygen to the flame. As a result the flame will become larger and generate more heat. This will make the air hotter, thus increasing the speed at which the air flows up the tube. This can create a strong updraft of air which will increase the rate of burning compared with the same fuel burning in the same burner in the open air.

This will give a similar result to the air flow caused by the pressure difference between the two areas at the nuclear site.

Considering the Browns Ferry fire and the well known effect of a tube on a candle flame (or flame from an oil lamp), I have to ask the question of “was it reasonable to place polyurethane foam in the gap between the wall and the aluminium sheeting“. I think knowing about the Browns Ferry fire and being aware of the chimney effect it is not reasonable to create this sandwich of wall, polyurethane foam and aluminium sheeting.

I think that the creation of a rapidly growing fire was something which is foreseeable. Some of my readers will be glad to know that giant wasps are not possible. Wasps which are the size of humans are thankfully not possible. I am very glad that in one of Clare Smallman’s books she pointed out that the breathing of insects can not be scaled up sufficiently to enable giant killer wasps to live, fly around and menace us. Thus by reading a biology text book as a young boy, Clare managed to preempt any nightmares about overgrown angry insects, thank you Clare !

Well I hold the view that Clare is a “rockstar biology teacher” who is in the same league as “Barry E. Tyler” who is a “rockstar physics teacher”, but we will have to leave these two educational superstars for another day. Sadly both of them have retired so I can not have my dream team of science teachers for my son Jacob.

While hindsight is a great thing which makes everything so perfectly clear, it does seem like a bad idea. I am interested to know if any fire experts who have a deeper insight into fire would be able to argue a safety case that the combination of the polyurethane foam blocks, the concrete wall and the aluminium sheeting was safe. My reasoning is that for a fire expert to argue that the system was safe then they need to explain their reasoning in public without hiding behind jargon. They will need to be able to communicate their ideas and reasoning to “technically-minded non-specialists” if they can argue a case to me that the system was safe I will write about it here. If any fire experts are reading who hold the view that the combination of concrete wall, polyurethane and aluminium sheeting was safe then I would like to invite you to write to me, I am willing to discuss the matter.

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