Eh? What is in your slurry that makes it unstable? AN in its various basic forms is very, very stable for long periods, hence its popularity. It is used as filler for gelpacks and slurries because it is very cheap, but AN is not the only ingredient in those.
They frequently spike slurries with other less stable explosives precisely because AN is a pain to set off, particularly in small charges. Raw AN is often classified as a tertiary explosive because it takes a fat high-explosive booster to get something resembling a proper detonation.
http://www.chron.com/content/chronicle/metropolitan/txcity/main.html
'Texas City just blew up'
A powerful chemical explosion 50 years ago propelled a small port town into an unwelcome national and world spotlight
Paul S. Howell / Chronicle
By STEVE OLAFSON
Houston Chronicle
TEXAS CITY - On the morning of April 16, 1947, shortly after 8 a.m., the hatch on the No. 4 hold of the French ship the S.S. Grandcamp was opened so that stevedores could resume loading a shipment of fertilizer bound for Europe.
snip
Just an historical note on fertilizer blowing up.
"The blast took nearly 600 lives and millions of dollars in property, and it scarred the town. A half-century later, people in Texas City celebrate their recovery, but still mourn their loss."