§ Sir A. Hurdasked the Prime Minister if he has yet received the final report of the board of inquiry into the fatal accident at Aldermaston on 26th February; and if he will make a statement.
§ The Prime MinisterYes. I have now received the final report of the Board which I appointed to inquire into this accident.
It confirms the conclusion in the interim report, of which I informed the House on 17th March, that the explosion must be regarded as an accident and did not arise as a result of negligence.
As hon. Members will recall, I also said then that the explosion occurred during the course of conveyance of high explosives by truck; that it was confined to the vicinity of one building; and that there was no outbreak of fire.
Two men were killed instantly, one was injured, and eleven other workers were treated for shock.
The Board has reported that there can be no doubt that the explosion occurred in explosives which were being conveyed by truck in a box which was missing after the explosion.
From an examination of the site it was clear that the explosion occurred at or about ground level, and that the explosive could have detonated in one of two ways; either the box containing it was lifted off the truck and was subsequently allowed to fall to the ground, or the box fell to the ground as the truck stopped.
The Board was unable to obtain conclusive evidence; but tests on a fragment of the charge involved in the explosion 61W which was available in the Establishment showed that the material was not so sensitive that it would be expected to detonate if dropped, in its felt-lined box, from a height of about two feet to the ground.
On the other hand, if the box fell when the truck stopped, and the explosive escaped from it and slid along the ground, the immediate effect at the points of contact would be a rise of temperature which could approach or exceed the ignition temperature and cause an explosion.
The Board therefore regarded the second possibility as the more likely, and was confirmed in this view by a number of independent factors and inferences, particularly in trials carried out on a similar truck.
The maintenance records of the truck used, and the truck itself, were examined after the accident, and it is certain that the explosion was not caused by any electrical or mechanical failure. Nor was there anything in the casualty and sickness records of the men involved to suggest proneness to accidents.
The Board recommended certain changes in the practice of the Atomic Weapons Research Establishment for dealing with explosives. These relate chiefly to the duties of the scientific and supervisory staff, the procedure for handling and conveying explosives, and the design of the trucks used.
I have referred the Board's recommendations to the Atomic Energy Authority, which has accepted and is acting on most of them, and giving further consideration to the remainder.