Further to your post concerning NWA here is two other books which may be of interest to anyone following the subject
GUIDE TO NUCLEAR WEAPONS - PAUL ROGERS ISBN 0-85496-1850-X printed 1988 gives a good idea of why so many NWA have happened when you see how many NUC devices there were
THE HIDDEN COST OF DETERRENCE, NUCLEAR WEAPONS ACCIDENTS - SHAUN GREGORY ISBN 0-08-037335-6 printed 1990 some intersting details on each known accident within this book
Both books are not new but give a good insight into the numbers of weapons and the type of accidents there has been
Hope this helps anyone interested in the subject