Can I make an explosions not kill instantly?

Explosions have a property called DestroyJoinRadiusPercent. Setting this to 0 will make it so that explosions don't destroy joints (thus not killing your characters.)

If you want to make it so that Explosions don't kill characters instantly BUT also deal damage, it's going to be a little tricky. You can accomplish this by using the Hit event of Explosions.

local EXPLOSION_DAMAGE = 10

local Explosion = [ Some explosion you created via script]
Explosion.Hit:Connect(function(part)
	if game.Players:GetPlayerFromCharacter(part.Parent) then
		local Humanoid = part.Parent:FindFirstChild("Humanoid")
		if Humanoid then
			Humanoid:TakeDamage(EXPLOSION_DAMAGE)
		end
	end
end)