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 Writings about things that have occurred in my life. Not in Chronological Order |
| Things that have happened in my life, good or bad. The entries will not be in Chronological order |
SL-1, The World's First Nuclear Reactor Accident I thought I'd explain a little bit about the dangers of Nuclear Power, so you understand why we were trained so diligently, and had to learn everything we could about the Reactor and Reactor Theory. The SL-1Reactor Accident occurred on January 3, 1961. You'll probably gasp at that date, but yep, that's when it occurred. Long before the 3 Mile Island accident here in the States, long before the Chernobyl accident in Ukraine, and of course long before the Fukushima Reactor accident in Japan. We learned about the SL-1 accident while in the Nuclear Power Pipeline, probably during prototype training in 1974 for me. Gosh, that was 'only 13 years' after the accident! If you're really interested to read about this, use the link below. https://en.wikipedia.org/wiki/SL-1 I attended Nuclear Reactor Prototype Training at the S1W facility in Idaho, about 10-12 Miles west of the SL1 Site. Let me tell you what I 'knew' about the accident, because it was horrendous. SL1 was an experimental Reactor, part of an Army project. The idea was for the Reactor to provide electrical power and heat for small, remote military facilities, such as radar sites near the Arctic Circle, and those in the DEW (Defense Early Warning) Line. Before I continue, you have to know that the Control Rod Speed is 2-3 inches per minute. That is so the Control Rods do not add Positive Reactivity too fast, which would result in a casualty like this. There were three male operators working on the SL1 Reactor the night of 1/3/61. The design power of SL1 was 3 MW (thermal), but some 4.7 MW tests had been performed in the months before the accident. Useful power output was 200 kW electrical and 400 kW for space heating. On January 3, 1961, at 9:01 pm MST, an operator fully withdrew the central control rod, a component designed to absorb neutrons in the reactor's core. This caused the reactor to go from shut down to prompt critical. Within four milliseconds, the core power level reached nearly 20 GW! (When the reactor is prompt critical, the time to double the power is of the order of 10 microseconds. The duration necessary for temperature to follow the power level depends on the design of the reactor core. Think about that. The Reactor power will double every 10 microseconds!) That is 6,666 times more than rated power! It went from Shutdown to 6,666 times more than rated power in less than 4 milliseconds. Unbelievable if you ask me. Let me explain what I can without compromising Confidential Material. First, a Control Rod. It's designed to essentially 'suck up' most all neutrons that core creates. Yes, that core will emit neutrons all the time, so by inserting the control rods fully, those neutrons are sucked up, the Reactor cannot go Critical. Why it emits those Neutrons is a natural phenomenon for a Reactor Core. Secondly, the Reactor Core. It is made of a certain isotope of Uranium. It will fission all the time by absorbing free neutrons which can cause fission to occur. Yes, can, not will, because neutrons can be absorbed without causing fission. You would have to know the six factor formula (Don't worry, I'm going in to that here) to understand all that, So, the core is meant to fission, a Control Rod does exactly what its name implies, it controls that Nuclear Fission. The actual cause of the accident is not known, the Operators did not write down their every action. It is theorized that the Central Control Rod became stuck. The operator then applied more upward force to free it. This resulted in it moving about 20 inches rapidly! This caused a massive amount of Positive Reactivity in the Core. Of course that resulted in this accident. There are other theories of course, they are discussed briefly in the link I provided. The intense heat from the nuclear reaction expanded the water inside the core, producing extreme water hammer and causing water, steam, reactor components, debris, and fuel to vent from the top of the reactor. As the water struck the top of the reactor vessel, it propelled the vessel to the ceiling of the reactor room. A supervisor who had been on top of the reactor lid was impaled by an expelled control rod shield plug and pinned to the ceiling. Other materials struck the two other operators, mortally injuring them as well. (In my training, we were told it was a Control Rod that impaled the man. Hopefully his death was instantaneous, but one of the men on the outer portion of the Reactor lived for a couple of hours. The accident released about 1,100 curies (41 TBq (Terabecquerel, yeah, it's easier to say TBq)) of fission products into the atmosphere, including the isotopes of xenon, krypton, strontium-91, and yttrium-91 (detected in the tiny town of Atomic City, Idaho). It also released about 80 curies (3.0 TBq) of iodine-131. This was not considered significant, due to the reactor's location in the remote high desert of Eastern Idaho. The accident caused SL-1's design to be abandoned and future reactors to be designed so that a single control rod removal could not produce very large excess reactivity. Today this is known as the "one stuck rod" criterion and requires complete shutdown capability even with the most reactive rod stuck in the fully withdrawn position. The big problem with Nuclear Power, what people normally protest against, is how long the core is radioactive above the limits set by the Atomic Energy Commission (AEC). Yes the core is far more radioactive than the AEC allows. You might wonder where the numbers came from. The Nuclear Regulatory Commission (NRC), determined that a short-term, whole-body radiation dose of around 400-500 rem (4-5 Sieverts) is considered the lethal dose for 50% of exposed individuals, causing severe radiation sickness and death within weeks, though doses over 1000 rem are invariably fatal, with death often occurring within days or weeks even with treatment, while lower doses (100-200 rem) cause milder sickness but are less likely to be fatal. So an expended core is very radioactive, and will be for a long, long time. Right now, US Navy Cores (and the sealed Reactor Compartments) are stored at the East Hanford, Benton County, Washington site. There are also plans to store spent fuel (and the sealed Reactor Compartments) in Western Idaho. Both locations are sparsely populated, and will be for a long time it seems. Think for a moment about the logistics and cost of this. The Submarines are deactivated, defueled, and eventually cut up at Puget Sound Naval Shipyard, the only shipyard that can perform this action. The Reactor Compartment is separated from the main hull and sealed. The Reactor Compartment is then placed on a barge for towing. It travels up through Puget Sound, out the Straits of Juan De Fuca and down the coast to the Columbia River. It is then towed up the river through locks and such to reach the town of Richland, Washington. Now it's loaded on to a truck and carted about 30 miles to the Storage Facility. WOW! SL1; an accident that is largely forgotten by the general public, Jim Dorrell |
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