Radiation level at Pennant Operation 'Z' Christmas Island

Currently waiting for a response from Ministry of Defence, they should respond promptly and normally no later than (details).

Dear Ministry of Defence,

The radiation level for Pennant bomb at Operation 'Z' , Christmas Island is recorded as ONE roentgen (10 mSv) . Could you please advise me as to the 'HALF VALUE THICKNESS' from the point of detonation, to the instrument recording the 1 roentgen?

Yours faithfully,
Dennis Hayden
on behalf of the Combined History Archive of Nuclear Veterans

Dave Whyte left an annotation ()

I doubt if you will receive an answer to your question as this would show an excessive amount of radiation at the test site. The detonation was 1500 feet above the ground and the half value thickness for air is 114 feet, that would make the half value 13 to ground level. Add on another 7 to reach the instrument and you are looking at a Half Value Thickness of 20.
Let us see the answer given by the Ministry of Defence/AWE, I expect you will be told they do not know!

Dave Whyte