oxygen
heat
light
moisture
are your enemies, fridges can be humid though... get yourself a rubber sealed mason jar, pop your seeds in there, fill the rest of the space with rice to displace unwanted oxygen (slice an apple, and watch it go brown, thats the free radicals attacking it, air is bad for preservation) and then stick it in the fridge...
A hole in the ground makes a good stealth fridge (still use jar though), just remember where the hole is

a hole under a stepping stone works.