When you store clams in the refrigerator they can safely stay in the refrigerator and stay alive in the refrigerator for up to 3 days.
After 3 days the clams can begin dying and will no longer be safe to eat as you can only eat the clams when they're alive.
Once the clams die they begin going bad and are no longer safe to eat.
Place the clams in an unsealed container and use some paper towels to cover them with and they should stay alive for 3 days.
If you put the clams in a sealed container then they will die so leave them in an unsealed container.