Fission product yield from MOX (which include some fissionable Plutonium) is virtually indistinguishable from “regular” reactor fuel of ~5% U-235 enrichment.
The fission products that are measured in the environment “get out” based on their physical characteristics - gases and iodine highly mobile, and to a much lesser extent, particulates like Cs or Sr/Y or Pm. The Uranium Oxide or Plutonium oxide in fuel is in ceramic form, and is not mobile – it may turn to rubble as fuel cladding “melts” (proved at TMI-2) but is NOT mobile and is NOT going to be released from the plant systems.
Bottom line, don’t buy into ANY hysteria about MOX. NO sample taken in the environment will detect Uranium or Plutonium. You don’t have to believe “radiation is good” to understand how these materials behave physically.
I think the problem most folks are having stems from the fact that most of what has been made available to the general public on radiation issues and issuances is primarily centered around explosive (critical) events, in particular bombs/warhead explosions and fallout.
When one considers that in those events there is a tremedous particulate release because an explosion is an intended and engineered effect, disseminating the materials remaining from the bomb/warhead and daughter products as well as whatever can be neutron activated in the environment, and the access to the environment unlimited, there is cause in those situations for concern.
However, power stations have been designed for just the opposite effect: to keep fuel elements contained, chemically, physically, and to contain the daughter products and radiation so people who work there can continue to do so, just for starters.
In addition, as much or more expertise has been utilized in an effort to design the plants to avoid the unintentional release of nuclear material.
The difference is that between a wildfire and the pilot light on a stove. They are both fire, but one is out of control, the other is designed to be contained.
That the plants are relatively intact, even if stripped of some of the supporting infrastructure after two record natural disasters is impressive in itself.
Considering the logistical difficulties of coping with these problems in a landscape devastated by those selfsame natural disasters, I think the Japanese are doing a great job.
I am well aware of the ability of the media to foment panic, and the levels of hyperbole to which they can go, I work in the oil industry on drilling locations and spent days (as did others) explaining downhole environments, wellbore physics 101, and basic geology to scientifically illiterate people who had been fed an incredible array of apocalyptic predictions by folks who had no clue (or more diabolically, knew better) about oil reservoirs or oilwell drilling.
I see a similar media dynamic happening here, with less than knowledgeable media personages feeding panic to the masses about events thousands of miles from the bulk of their audience, in what appears to be an attempt to foment panic.
Terrified people are easily led into making decisions which may seem intelligent and rational in the height of confusion, but which are counterproductive and even harmful when viewed calmly.
We are still being inundated by survivor/refugees here in North Dakota, not of the 1000 foot wall of water that was going to wash the Gulf Coast States clear of humanity after the floor of the Gulf of Mexico imploded because all the supporting methane ran out*, nor the survivors of the methane explosion which blew up everything from the Bay of Campeche to Missouri and beyond*, but from the economic devastation foisted on thriving communities by the drilling moratorium.
(* actual apocalyptic scenarios, at their internet worst)
Now, those who take advantage of such events on the internet and elsewhere to gin up the sort of stories which would have been rejected by Batboy himself as a bit too fanciful, have been up to their old act of turning disaster into a real moneymaker by getting webhits and selling ads for everything from lead-lined band-aids to radiation suits, while calling for greater seismic protections and tsunami proofing facillities hundreds of miles from the nearest ocean or seismic area.
On this issue, it has been good to read that there are those whose area of expertise is in this field, and see them fight the unwarranted panic in areas far removed from the problems in Japan, while they explain and defuse the misreporting of the media and provide realistic expectations for the outcome there and its effects on the world.