Hi Mongo:

___Believe me, nothing like Chernobyl ever came close to happening at TMI U2 in PA. Approximately 2/3 of the core did melt but it was contained in what all western based reactor designs have and call a Containment structure. This structure was designed for the exact reasons that happened at TMI. When a Core melts and the entire RCS (Reactor Coolant System) or a large percentage of it is turned to steam, the size of the structure is large enough to contain the mixture of H2O and radioactive gases below ~ 50 #’s so as to not break the Containment structure or vessel. This is what saved TMI … From my understanding; the maximum dose received from someone off-site was < 50 mRem. Being a nuclear plant worker, I have received more then 50 mRem in a day just doing a higher then normal dose job if that helps you quantify what amount of radioactivity was released from TMI as well as what 1 individual received. Most everyone else received doses far smaller then this and in fact, were probably much closer to background then the anti-nuke zealots would have you believe. I do have to be careful as there were significant releases as measured at the purge exhausts but it is what actually accumulated that matters … Every citizen in the US as an example receives between 100 and 300 mRem/year from natural occurring radiation just by living on the planet. All bets would be off however if the fuel itself does not stay in a specific geometry, fuel cladding had split open, the RCS piping ruptures, and then the containment itself were to be breached in some fashion. There would have to be quite a bit of damage to knock out all of these fission product barriers to even come close to a TMI like event let alone one the magnitude of Chernobyl.

___The Russian designs did not add this containment structure on any of their plants to save billions of rubles in the cost of construction … I don’t want to go too far out here but the Russian based designs have what is called a Positive moderator coefficient core structure of a completely different makeup then what western based designs use. As the fuel in that specific type of core heats up, more neutrons that can produce the next generation of fissions becomes likely. This cycle can get out of hand in seconds as what happened at Chernobyl with all the safety systems being removed as they were. In the US and every other Western based reactor design that I know of, the cores are negatively moderated throughout most of the fuels cycle. In other words, as a core heats up, there are less fissions producing a particular speed neutron which in turn creates even less fissions in each successive generation. This continues until a lower equilibrium (power for all intents and purposes) is reached. Another item (the most damaging in the case of Chernobyl) was that there was an outside grid engineer/manager/military individual running some very ill advised coast down from power tests at Chernobyl (he outranked the senior manager(s) running the plant). He had the Licensed Operators place every safety system available in a non-functioning configuration to perform this grid power availability after trip and coast down test. The safety functions would have prevented the non-sensical test so this outsider ordered the multiple safety functions removed from service. There were plenty of operators and managers that that did not want to do this but were basically forced to do what they were told as you can imagine how the old Soviet system worked …

___Here in the US, if someone were to remove a safety system(s) like that (even one), he would be removed first from the control panels, then the control room, and then the plant site by armed guards. There is also a highly trained hierarchy to prevent that kind of non-sense from happening anywhere in the west that I know of. Anyway, even with TMI’s multiple failures, the containment was the last line of defense and it held as it was designed to do. Today, the nuclear industry is held to a std. so much higher and far beyond those days so many years ago that it is an entirely different industry imho. About all I can add is that there are much higher trained operators and managers, much better controlled plants and the equipment that resides in them, and a much stronger group of industry watchdogs looking over everyone’s shoulder to make sure screw-ups like those in the past never happen again. I cannot give you an example of how well trained and safe the plants are because of this training and absolute adherence to specifications the plant has to be in at all times for 100% safe operation but it was a task as noble as when Kennedy decided we were going to the moon. TMI was definitely a wake up call and the Industry has not forgotten nor has it ever been in such straights in terms of safety since.

___On the other side of the coin, the Power industry as a whole has a problem facing it because of all the wheeling of power. This is where privatization and the all mighty dollar at all costs come into play. What is unsafe today imho is not the power production from the nukes, coal, gas, hydro, and even a few wind power plants that supply your power but the wild swings that power sales are generating on lines that were not designed for it … The recent Northeast blackout was just another symptom of this and I can only hope the future will provide more power reliability but not that much has changed since the last big one. I am not all that confident of a higher reliability in the near future either … At least the Load Dispatchers around the country have more guidance as to when they can isolate the overloaded sections into islands so an event cannot cascade into something much bigger. Like anything else where money is involved, there isn’t any one company paying to upgrade the grid. For all intents and purposes, deregulation placed the company that used to own the grid at an extreme disadvantage to keep it upgraded as IPP’s (Independent Power Producers) simply tap into it and start selling power at whatever the grid price is or through whatever contract sale they have setup previously. I do not know much about Grid ops so I may be speaking well beyond my actual knowledge in this last paragraph.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net