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Nuclear Popcorn


A newly declassified report from the Ministry of Defence has revealed 
for the first time that a nuclear accident could result in a significant
nuclear yield. JSP 538 Regulation of the Nuclear Weapons Programme says
that where there are a number of nuclear weapons in the same vicinity
then a very low yield from the detonation of one warhead could result in
a significant yield from another warhead.

Regulation of the Nuclear Weapon Programme, JSP 538, originally RESTRICTED, 
has recently been declassified. Annex F contains the Nuclear Weapon Principles
and Safety Criteria. Para 34 of this annex says:

"Popcorning can result from a sequence of accidental detonations of nuclear WHs 
[warheads] in close proximity in which it is possible for a very small nuclear
yield from one WH to enhance the yield of another WH in the detonation sequence.
The potential for popcorning can only exist when there is a precise timing
relationship between detonations. Although each WH may individually be SPS
[Single Point Safe], popcorning may have the potential to produce a significant
nuclear yield.

"The probability of yield from popcorning depends on the array geometry and the 
SPS characteristics of individual WHs ..."

In 1994 John Harvey and Stefam Michalowski co-authored a report in Science and 
Global Security on Nuclear Weapons Safety: The Case of Trident. This described how
Trident warheads or Reentry Vehicles (RVs) are located around the explosive third
stage of the missile. The report explored how this arrangement might lead to a
nuclear yield:

".. what happens if, as a result of gunshot for example, a detonation is initiated
on the periphery of the rocket motor directly adjacent to one of the RVs? A non-
symmetric shock could generate flying case fragments that would strike that RV
causing a one-point detonation of the warhead. As the detonation front proceeded
through the propellant, creating additional case fragment impacts on RVs, fragments
from the first warhead would be striking adjacent warheads. If the timing were just
right, one might argue that the HE of an adjacent RV could be detonated at more than
one point, perhaps creating sufficient compresssion to produce some nuclear yield"

Today one of the authors, John Harvey, is responsible for policy, planning, assessment
and analysis at the NNSA, the agency that runs the US nuclear weapons programme. Stefan
Michalowski is now senior scientist at the OECD in Paris. Commenting on the new
disclosure Mr Michalowski said: "The explosion of a boatload of missiles in a port would
be an unimaginable catastrophe. ... It's a very, very scary thought".

The disclosure of the dangers of nuclear popcorn, uncovered by Scottish CND, comes shortly 
after the release of a series of Board of Inquiry reports into serious accidents on British
submarines. These reveal a catalogue of failures and undermine any confidence in the
MoD's ability to assess the risks associated with operating nuclear powered and nuclear
armed submarines.

This was first reported by Rob Edwards in the New Scientist and on robedwards.com.

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