I have a little more time, so I will give you some more information. First, have you verified that the internal cracks are present prior to baking? In my experience with powered metal, most internal cracks are caused by shrinkage during the sintering process. It is indeed a tricky process, and one which does not lend itself well to most non-destructive methods. If your part is not large(less that an inch or so in its thickest cross section)a low power real time x ray system is your best bet. There are many companies which produce low-power systems(less than 75 kv) for inspection of food products. These systems scan product on a conveyor belt, which would minimize handling on your part. Also, most low power systems as found in airports will do the job nicely for you, and they have image enhancement software which can make detection more accurate. There are many considerations however when looking at this method. Part geometry, indication size, cost of the system,(you may be able to rent one)
training, safety, and so on.
I agree that the best thing to do is improve your process, however without a quantative method to measure the severity of the problem, process impprovement is difficult with this manufacturing process.
Any more questions, please let me know!