Talk:SL-1

2003
Just starting out - more on SL-1 and other topics to come. Brian Rock 03:03, 4 Dec 2003 (UTC)

Just found an entry for SL-1_Reactor_Accident, as I've learned to better navigate. I'll be merging this article into that one. Brian Rock 04:26, 6 Dec 2003 (UTC)

The SL-1_Reactor_Accident article doesn't follow the Wikipedia naming convention, so it's better to merge that description into this one and make it redirect here. Nothing links to it, perhaps because of the name. This one gets several links, probably because it has the most obvious naming. Jamesday 12:05, 8 Dec 2003 (UTC)

2004
What are the names of the three victims? --Mizchalmers 22:32, 8 Sep 2004 (UTC)
 * This link http://www.radiationworks.com/sl1reactor.htm names the victims --Zdv 04:18, 13 Sep 2004 (UTC)

Zdv, Why have you removed my open link to prompt criticality in SL-1? I understand removing a redirect to nothing, but highlighting an obviously non-trivial term is deliberate and done to prompt the writing of a new article with that name. Your actions are not good editorial practice. --Azazello 02:39, 28 Nov 2004 (UTC)

Suicide-homicide
I think it is now proven fact that the explosion happened due to sabotage (homicide-suicide), because one operator learned that his wife is cheating with the other operator and decided to take the amoroso with him to the afterlife. The third, unconnected operator was just "collateral damage", so to speak.

Human passion is stronger than the atom. —Preceding unsigned comment added by 195.70.32.136 (talk • contribs) 10:36, 7 December 2005 (UTC)


 * One of the theories, but hardly a proven fact. Read Idaho Falls for what I think is the definative public account. The operator who pulled the center rod out too far, John Byrnes, was recently separated from his wife (crashing at friend's places for the last several nights) and had money problems. Byrnes was mostly at fault in the marital strife: he was a philanderer and drunk.


 * Richard Legg's wife was a local Mormon girl, several months pregnant, and by all accounts hardly likely to be engaged in any kind of relationship with Byrnes. Most likely, they never met. Both the widows Legg and Byrnes have denied there were any extramarital affairs among them.


 * The murder suicide rumor had swirled around the industry for years following the accident. It became a semi-official claim when a nuclear safety researcher repeated the rumor in a memo stressing the importance of making reactors operator-proof. Previous reactor safety guidelines always assumed the operators were in their right minds when at work, and instead concentrated on commies with grenade launchers.


 * The most plausible reasoning I've read was Byrnes resented Legg because Legg was recently given a supervisory role. They had fought some months earlier at a bachelor's party (both men were drunk, and Byrnes had just fucked a whore--Legg probably taunted him about it). Byrnes had a temper, and had been known to throw shit around inside the reactor control room when frustrated. He was recently passed on the same supervisor job Legg now held. The men were several hours behind in their night's task list. Legg (a pranskter and under scrutiny for poor performance as a supervisor) probably said something to chide Byrnes (perhaps officiously restating the rule that the control rod mustn't be raised too far, or telling him to "excersize it" to prevent sticking), and Byrnes just had a "to hell with this" moment and raised the rod too far to piss everybody else off. Kaboom.


 * There's no evidence anybody, least of all the poorly trained operators, knew that withdrawing the rod too far would lead to an explosion. They guessed it could possibly melt down the core, but that wouldn't constitute a murder-suicide.
 * Tafinucane 21:30, 27 December 2005 (UTC)

Causes ideas
From the article:
 * The three most common theories proposed for this discrepancy are sabotage or suicide attempt by one of the operators, inadvertent withdrawal of the main control rod, which was known to be "sticky," or an intentional attempt to "exercise" the sticky rod, to make it travel more smoothly within its sheath.

Suicide is right out, since the designers didn't even know you could cause an explosion by withdrawing the control rod too far. The main control rod was the only control rod that didn't have a history of sticking. Not to say that it didn't stick that night, just that it hadn't before. AEC investigators made extensive trials to reproduce the accident by having men pull on mock-control rods and releasing the rods suddenly. They also tried goosing the men (giving the test lifters an unexpected pinch in the rear, as Legg was suspected of having done), but never were the 100-lb bars lifted more than a few inches. Similarly, the "exersizing" the operators had been doing previously only consisted of sliding the rod up and down a few inches.

The article's statement remains true, however, that those are the three most common theories. The article needs to also mention that the reactor design was also to blame. The control rods could get stuck, as mentioned. Withdrawing a single center control rod could send the core to critical (which is a reactor flaw unique to the SL-1 design). Boron "poison" meant to quell the excessive radiation when the uranium fuel was new was supposed to be alloyed into the fuel itself. This proved to great a metalurogical challenge for the time, so they just tacked on boron-alluminum allow strips to the fuel. The strips flaked off over time, so the degree of control the operators had over the nuclear reaction was narrowed and partially unknown. Tafinucane 21:05, 28 December 2005 (UTC)


 * There was an article on this in one of the science magazines in the 1960's. I don't recall which one, could've been Popular Science or Science and Mechanics. It had a few photos, including one of the flaked and swelled boron "poison strips" that frequently caused the control rods to stick. The theory it presented was that the strips caused the main rod to stick and the operator had to pull hard on the rod to reconnect it to its motor drive. The rod popped free and *boom*. IIRC it said that a different crew had been there earlier to service the control rod drives and had left it to the next shift to reconnect them. —Preceding unsigned comment added by Bizzybody (talk • contribs) 04:45, 27 November 2008 (UTC)

Problem with date
I'm not sure if the SL-1 accident took place on January 3 (1961). I have a Ryszard Szepke's book in which it is written that the event was on January 10. Please, verify this information. —The preceding unsigned comment was added by Krzy B (talk • contribs) 20:14, 12 April 2007 (UTC).

Steven Casey in Set Phasers On Stun reports that the accident took place on January 3, 1961.
 * Casey, Steven (1998). "Genie in the Bottle". In Set Phasers On Stun (2nd ed.), p. 117. Santa Barbara, Aegean Publishing Company.

—Iain marcuson (talk) 01:35, 29 October 2008 (UTC)

Röntgen -- rubbish text?
My edit was intended to fix the link for Roentgen to point to the unit of measurement rather than the disambiguation page. Although it appears as R%C3%B6ntgen in the edit summary, the text appears properly in the rendered page in my browser and the link in my revision points where I intended. Is there a problem in other browsers or is the "rubbish text" just in the edit summary? Langhorner 13:15, 28 August 2007 (UTC)


 * Hi there,I am very sorry, and you are correct, your version does appear correct in the rendered page-to me the edit appeared as rubbish characters-as you described. Next time I'll be a little more careful before I jump on perceived vandalism. your edit does appear to fix the link! i'll revert my own (incorrect) edit.--Read-write-services 22:51, 28 August 2007 (UTC)

Weight of "the" control rod
My recollection from many years ago is that the operator's actions regarding over-withdrawal were established by after-accident analysis to be intentional, though his reasoning for doing so remained unknown. Reasoning: the weight of the control rod was fairly substantial (75 lbs or so?) and precluded an unintentional move of 16 inches or so, including the scenario of the sudden freeing of a stuck rod. Reconstruction via manual tests, including stuck-rod scenarios, confirmed this (again, as best I can recall). However, I'm so-far not able to find a reference for the weight of the rod. At this point, I can only leave this note for future editors' consideration. --71.42.142.238 18:57, 5 October 2007 (UTC)

Parting note: I can't help but comment that the whole thing leaves one wondering as to why they weren't simply employing a mechanical or hydraulic jack of some kind to move the control rod, stuck or otherwise. It just doesn't pass the common sense test to not use one, especially if the rod was sticking...and known to be somewhat heavy...and highly reactive. Whatever...but it seems that a car jack would have done the trick. --71.42.142.238 19:22, 5 October 2007 (UTC)

The rod weighed 84 pounds, and the tests done by many men determined it was feasible and had been contemplated by the reactor operators in case the Russians attacked (I kid you not). See the Stacy book, it's free online. I like to saw logs! (talk) 13:01, 6 March 2011 (UTC)

"Jordan redector"
As far as I can tell, Jordan is a company that does manufacture dosimeters and the like. But a "redector" is likely a misspelling of "detector", and in any case, I don't see the point of pointing it out as a Jordan model. I'm going to revert this phrase to the verbiage as of two years ago, at here: http://en.wikipedia.org/w/index.php?title=SL-1&oldid=11833643 John Sheu 23:53, 21 October 2007 (UTC)

Additional citations needed
I've added a {MoreSources} tag to the top of this article as many more citations are needed to support what is being said. Please see WP:When to cite for guidance and some of the WP:GA articles for examples of how this is best done. Johnfos (talk) 02:24, 19 December 2007 (UTC)


 * There are plenty of sources referenced and cited. Do you have concerns about specific sections not being sourced? Please be as precise as possible, I don't quite get what your current objection is. Thanks. Georgewilliamherbert (talk) 02:33, 19 December 2007 (UTC)


 * The specific problem is that as I read through the article, there is no indication about where the information being provided has come from. Sure, there are many unnumbered "References" listed at the end but there are very few links (citations) between specific references and particular parts of the text. So, in most cases, there is no way for the reader to check a particular piece of information against the specific source used. And so the content cannot be verified. This is just not satisfactory. Johnfos (talk) 11:04, 19 December 2007 (UTC)


 * I am sorry that we're asking you to actually read the sources. The references are voluminous, and citing each paragraph as to where a description of it appears and in what sources is possible, but clumsy and pointless. There are a number of detailed accounts of the accident in the sources. All the specifics are accurate. Having to read the references does not mean it's unreferenced.
 * If you would like to make it easier for people to specifically find a link for particular information, take one of the overall DOE reports (the Interim Report is a good place to start) and make links to pages.
 * But you shouldn't tag an article as needing references when it's got them. I'm going to delete the tag. Georgewilliamherbert (talk) 20:07, 19 December 2007 (UTC)


 * Georgewilliamherbert, what I believe is being asked is that the facts as they are presented in the article be wiki-referenced. There's a particular way to place a tag next to a piece of text that allows Wikipedia to create a list of reference tags automatically. This is prefered for many reasons, the biggest of which is the ability to reuse named reference tags or correct all uses of a reference tag by simply correcting the first instance. Take a look at Citation templates page for the different ways WP has for citing references. There is no need to cite a specific paragraph/line/word in most cases, a simple citation of the book or article is usually enough. For example I changed the two initial references to wikirefs which now renumber the other wikirefs near the bottom (in the movie section).
 * Having said that Johnfos, could have just done the ref edits and showed Georgewilliamherbert what he meant. I think requesting a 3O was simply lazy on your part. Padillah (talk) 21:00, 19 December 2007 (UTC)

I read about this on the WP:3O page and decided that what's needed for now is a more appropriate tag, namely the {citations} tag; see if you all agree (I have placed it on the article, so read what it says). Hopefully some helpful editors will take the hint and move toward improving the citations. But don't be bashful about adding {citation needed} tags wherever you feel a reference is needed. Dicklyon (talk) 00:23, 24 December 2007 (UTC)

Leave Chernobyl alone
Why does this page and Three Mile Island's page always mention how these two reactor designs were much better then RBMK? The three had accidents, for chrissake. You don't go on comparing designs when you are talking about malfunctions. The negative void coefficient didn't help to prevent the core at TMI from partially melting, and didn't prevent the explosion in SL-1. What does mentioning Chernobyl here helps to explain? It seems like someone wants to say: "Even though this one exploded, it was still much better then the commie nucular plants." -- NIC1138 (talk) 16:22, 22 April 2008 (UTC)


 * Of course you go around comparing designs when you're talking about malfunctions. All of modern safety design is based around safety in depth; even though things are going wrong, it's all about not going too wrong. Yes, Air France Flight 358 burned to the ground after landing, as did Saudia Flight 163; so why did one have a 100% survival rate and the other a 0% survival rate? Furthermore, comparing reactor designs gives readers insight into what the features of this reactor mean, and what the other options were.


 * And, well, all politics aside, there's no question that Chernobyl and friends sucked, that they failed to learn lessons from SL-1 and Windscale despite 25 years in which to learn those lessons. There's a huge difference in loss of life and economic damage between Chernobyl and Three Mile Island. That's a point that should be made, that Chernobyl cannot be taken as the end-all and be-all of nuclear reactors. Frankly, I think that nuclear gets a bum deal, that we mention a bunch of nuclear accidents that caused no injuries but far from every fatal coal mine incident.--Prosfilaes (talk) 23:02, 22 April 2008 (UTC)


 * I agree I exaggerated about we being able to compare... But my fear is that we might be comparing different things. This talk about negative void coefficient being more "stable" sounds to me more like a subtle (and desirable) characteristic of the dynamic of the reactors in proper operation then overall safety under accidents. It seems to me some people are trying to pin-point this single characteristic of the reactors as a sufficient reason to consider the American reactors safer than the Sovietic. This makes difficult a more detailed discussion. Negative or positive coefficient, both Chernobyl and SL-1 had the rods improperly removed when problems began. The reactor at TMI, on the other hand, was being shut down. What if it were under operation? It partially melted even without the water mediating the reaction, imagine if the rods were out.
 * There are (were) many problems with RBMK and with SL-1. I just believe there is too much emphasis in this article on the void coefficient being positive or negative... Nuclear reactors use chain reactions, which is an inherently unstable phenomenon being controlled by several factors. So, it's always difficult to understand when a reactor would be more "stable" than other. More importantly: I believe in all accidents we had more water vapour then we wanted in the reactors. I'm not sure if the conditions were inside the scope of the this coefficient, which I believe models a linear operating point of the system, with liquid water. It's not easy to extrapolate the behaviour of the three reactors in pathological conditions just considering this coefficient...
 * Now, regarding details in Chernobyl's design, according to the wikipedia page on the Chernobyl disaster the control rods there were not fully graphite, but just its end tips. I'm not sure that what this article here is stating regarding Chernobyl is coherent with this other article... Plus, the RBMK design was largely modified after Chernobyl, but kept the positive void coefficient. Does that single characteristic suffice to say that it is still an "unstable" design, and that because of this it is still inherently more dangerous than TMI or SL-1?...
 * And regarding lessons from SL-1: did Chernobyl have a too high thermal resistance, as SL-1, or a too high sensibility to the effects of removing a single rod?
 * I'm sorry if I am sounding a bit harsh in these comments, I would like to have a little more time to write properly. I'm just an electrical engineer wanting to learn science, and to avoid any kind of political arguments!... -- NIC1138 (talk) 01:10, 23 April 2008 (UTC)

Contractors? Construction timeline?
In other sources, I find references that contractors' representatives were visiting the site, etc. I can't seem to find the name of the primary contractors on the project. Was it the U.S. Army Corps of Engineers? Westinghouse? Who? If this were an article entirely on the accident, it might not be as relevant. But in an article on the reactor itself, it certainly seems relevant -- "built between June 2040 and January 2041 by Spacely Sprockets," certainly would be a useful fact to include. This article actually starts with a maintenance shutdown, which obviously implies that it had been operational for at least one period previously. --Thatnewguy (talk) 13:48, 22 May 2008 (UTC)
 * I don't have a copy of the references handy but I'm pretty sure the maintenance was handled by the Army itself and the construction was done by military personnel. I think that the design was probably contracted out, but I don't know who made it. IIRC, the reactor was operational for a year or so--long enough to discover that the control rod channel was getting clogged by material rubbing off the walls. Protonk (talk) 20:35, 22 May 2008 (UTC)

Inherent Safety of a Water Moderated Design
"The accident also showed that in a genuine extreme accident both the vaporizing of the core and the water to steam conversion would shut down the nuclear reaction. This demonstrates in a real accident the inherent safety of the water moderated design against the possibility of a nuclear explosion."

I could be wrong, but isn't this balony? if the moderator has a negative co-efficient, then the reaction is shut down and you don't *get* a core which "safely ends the excursion by exploding".

Arguing water moderation is safe because the steam explosion destroys the core (which causes massive local contamination, plus potentially larger scale contamination depending on chance and circumstance), which ends the excursion, seems absolutely duplicious, when a negative co-efficient moderator would end the excursion *without* exploding the core.

Toby Douglass (talk) 12:28, 2 January 2009 (UTC)


 * For one, in theory there is no steam explosion, merely water to steam conversion that reduces the moderating effect enough to shutdown the reaction. For another, in practice, even on SL-1, which had a pretty minimal safety shell compared to any modern nuclear power reactor, there was negligible larger scale contamination.


 * More importantly, saying that something else is safer doesn't change whether or not this design is fundamentally safe, and this statement is about what was seen at the time about this design, not what can be seen from our current time-position about various designs.--Prosfilaes (talk) 23:17, 2 January 2009 (UTC)

Toby Douglass, Prosfilaes this was intended to address those unfamiliar with nuclear power who are worried about power reactors becoming nuclear explosions. The design was safe against that and one of my goals when describing the incident was to explain to a lay audience what happened and why it couldn't have become a nuclear explosion. Even after it killed or disabled everyone looking after it, with talk that it might have been deliberate, the design still shut itself down to the point of becoming definitively subcritical in this event. That's a success story. Not a good enough one, but it beats the alternative fears that many in the general public have.

It's still grossly unacceptable today and you're completely right that there are more inherently safe designs around. We can do without more successes like this but they still beat failures to protect the general public. Jamesday (talk) 13:18, 12 February 2010 (UTC)

At least one wrong date; added a link.
"abandoned its reactor program in 1965" I'm a veteran of the Army Nuclear Power Program, and I served there from March 1968 to March 1971. Best I recall, the program shut down around 1974. Several years ago I had a website on the ANPP (and the Army Air Defense Command Nike missile system), and I had some materials from other ANPP vets who knew the folks killed at the SL-1, personally. I don't know, however, being a newbie, how I can incorporate any of that here, since it would be hearsay and not reference-able. Also, there was a comment above about "poorly trained operators." That, I can from personal experience assure you, is nonsense. The ANPP program was quite rigorous (I was a licensed Control Room Operator, and for a time the Health Physics Supervisor, of the SM-1 at Ft. Belvoir). Also, I added a link for "health physics" since many readers won't know what that is. Rb88guy (talk) 02:39, 6 January 2009 (UTC)

Impaled by "the" control rod?
Was the operator impaled by "the" control rod, meaning the central control rod or was he impaled by another control rod? The "Idaho Falls" book says that there were several control rods. Was the operator squatting over the top of one while working on the central control rod? Tashiro (talk) 22:03, 8 October 2009 (UTC)

We were always told in debriefs of the accident at the INEL (late 1980's) that it was the central control rod, which was moved by hand. He was presumably leaning over the reactor moving the rod when the criticality excursion occurred. Shirakhan


 * Nope. First, it was the supervisor (Navy) standing by the guy yanking the control rod who got nailed. Second, he was impaled by the control rod's shield plug. This all likely happened when the vessel and the 2 men hit the ceiling. The rod actually fell back down. In fact, the center rod inserted itself far enough to ensure a good safety margin for the reactor to keep it shut down. I don't know which shield plug impaled him, but it wasn't from the center rod. I think maybe 2 or 3 rods didn't go back into their slots and merely fell on top of the vessel, but the fact that most of the water boiled away kept any further reaction from happening as much as the rods in the core. I like to saw logs! (talk) 13:16, 6 March 2011 (UTC)


 * That's great, but we need a citation to use it in the article.--Prosfilaes (talk) 21:53, 6 March 2011 (UTC)


 * Read the book by Tucker. Every gruesome detail is in there, because he finally got at least a redacted version of the autopsy released... the doctor who did it died in the last few years. The old guesses as to who was who were wrong for a few reasons... #1, the original identifications of the 2 bodies found first were confused. #2, the identities of the dead men were purposely undisclosed in practically every publicly available story of the events. People assumed that the one impaled was the one who pulled it, but there are plenty of reports which say that the central rod did NOT stay in the ceiling... it went back in. Also, the location of the entry wound would make it hard to believe that he had pulled the rod up with his hands. Just read the SL-1 article and follow the links to Tucker's book. Follow the ISBN link, go to Google or Amazon, and do a search for "Legg" or "impaled" or "control rod" or "autopsy" or "shield plug" and you can read the sections that are pertinent.


 * But here is the "Summary" which you can view for free, with many of the details you seek: http://catdir.loc.gov/catdir/enhancements/fy0904/2008013842-s.html (this is linked in the SL-1 article). It appears to have been the #7 rod's shield plug. I like to saw logs! (talk) 06:59, 7 March 2011 (UTC)

Prompt Criticality is a function of delayed neutrons, not thermalization
Whoever wrote the section on prompt criticality seems to be confusing two important concepts in reactor control: prompt criticality and fast fission. Prompt criticality is determined by prompted and delayed neutrons. Fast fission is determined by fast or thermal neutrons. "Prompt" and "fast" are not the same thing.

Fast fission occurs when a high-energy (i.e. not thermalized) neutron splits a nucleus, usually U-238, which would simply absorb a thermal neutron. Fast fission happens all the time, and is a minor contributing component of the overall reactivity of the core.

Prompt neutrons are created by the fission of a nucleus. Delayed neutrons are released during the radioactive decay of certain fission products, and they occur up to several seconds after the initial fission. Prompt Criticality occurs when the core achieves criticality using only prompt neutrons (i.e. those produced by fission alone), and the additional "delayed neutrons" released by fission product decay serve to accelerate the chain reaction to a state of supercriticality (i.e. increasing power level). Prompt Criticality has nothing to do with the thermalization time of the neutrons.

The explanation of how the accident occurred seems to confuse these two concepts (unless they're teaching a whole new kind of nuclear engineering now than they were 20 years ago). Would take some effort to disentangle the two.Shirakhan —Preceding undated comment added 19:00, 16 October 2009 (UTC).


 * Shirakhan, your point is noted. I just read through the article and indeed it's my judgment as well that the reactor physics and kinetics discussion in that section were misleading and seemed confused particularly on the issues of delayed neutrons and moderation. I've attempted a quick fix; give it a look. Much more could be done to make this article accurate, documented, and comprehensive. I hope some other people with particular expertise in the subject will kick the can down the road.--Carlwillis (talk) 10:00, 11 November 2009 (UTC)

I worked out there a little
Not right at SL1 and post-accident. But at the site. It is an eerie place. It really resembles something you would expect in Nevada or the like. The climate is a true dessert (less than 10 inches per year rain), more arid than most of the arid Southwest. Nobody lives near the site. Everyone drives or more usually is bussed in (this is a lot like the Nevada test site, I've also been there and it is eerie too.) You could LITERARALLY blow up a big atom bomb at the site and people in nearby towns would be OK. I'm not saying a reactor is a bomb...but it seems like they were super cautious when siting this stuff at the beninging of the atomic age. There are all kinds of little tiny antelope (well really small) that run around. They have the use of the site since there is no hunting there. It's really an amazing place... —Preceding unsigned comment added by 69.250.46.136 (talk) 17:49, 1 November 2010 (UTC)

The reactor core "vaporized"?
The article repeatedly says that the core and its components vaporized. That's usually a term for liquids... or for magic. Which is it? The fuel plates made of aluminum probably did not turn into a vapor. The article makes this assertion SIX times (as a verb form) for the core, whereas it mentions the water vapor as a (noun) ONE time. I think we need a revision here unless someone has some temperatures to corroborate this. I like to saw logs! (talk) 12:55, 6 March 2011 (UTC)


 * Okay, to answer my own question, the fuel in the core apparently did vaporize. Although a prompt critical reactor can be shown to avoid a core meltdown and vaporization, the huge amount of positive reactivity (well over $3, with one dollar being prompt critical) caused the fuel to literally fly apart before the water boiled to steam and appreciably cooling it. I would imagine the Maxwell–Boltzmann distribution of the atoms made the fuel quite erratic to pin down what phase it was in! This is reported in IDO-19313 Additional Analysis of the SL-1 Excursion, Final Report of Progress July through October 1962, November 1962. I like to saw logs! (talk) 07:33, 15 March 2011 (UTC)

Firefighters
I personally know Bob Archer (Rupert Idaho) one of the first responder firefighters. I asked him for the names of those firefighters on duty who responded to the incident. He named Ken Dearolon Asst Chief, Mel Hess Lt., Bob Archer, Carl Johnson, Egon Lamprecht, & Vern Conlon. I have added their names to the page. According to Bob, he and Egon are the only ones still alive. As a side note Bob has never had cancer! --Tomhung357 (talk) 15:32, 8 April 2011 (UTC)

Cleanup
In the fourth paragraph "Results from the surveys indicated that cesium-137 and its progeny (decay product) are the primary surface-soil contaminants." I do not believe that the product of Cs-137 decay, stable Ba-137 possibly as the carbonate, would be a significant source of contamination. Darian2 (talk) 03:17, 16 September 2012 (UTC)


 * Well if cesium-137 decays to barium, isn't its poisonous nature enough to be a "contaminant"? The sentence doesn't define what sort of contamination it is speaking of. In any case, 137m1Ba can be detectable in the debris with instrumentation that can find the characteristic 661 KeV gamma rays. 95% of the cesium will therefore emit this gamma on top of the already significant contamination beta of 512 KeV. The beta is indicative of contamination. Since its progeny emits the gamma a few minutes later, I would call this a contaminant. And if the cesium/barium (meta state) are indeed so plentiful after 50 years, they would surely top the list of any other contaminants as far as abundance and radioactivity goes. Strontium-90 might be a distant third here, especially since no one is crawling around the Idaho desert where SL-1 blew up and it is unlikely to get mobile in the environment there.

See http://en.wikipedia.org/wiki/File:Cs-137-decay.svg I like to saw logs! (talk) 07:20, 17 September 2012 (UTC)

New Personal Testimony on Cause
At that time, I worked at the OMRE (Organic Moderated Reactor Experiment) which was a couple of miles west of the SL-1 reactor. It was clearly visible from where I worked. That night I had worked until 9 PM, which was about the same time as the SL-1 explosion. I drove home, going right in front of the road to that reactor; but emergency vehicles had not arrived yet, because they were stationed further away from the SL-1 than where I worked (they arrived about 5 minutes after I drove by). When I drove by, there was no visible evidence of any problem.

The next day, reports started coming to us regularly. Most of the report here and on YouTube is accurate, but not all. It was stated that the truth could not be told since the Army would give a large cash donation to anyone’s family who was killed by a military accident. But no such donation could be given to anyone’s family if the military person died from their own accident. This was clearly an accident caused by these three men, not a military accident. Here are some unmentioned facts that I was told in the hours and days following that accident.

There had been several alarms from the SL-1 reactor over the past few weeks or months, and the emergency vehicles always went to find the problem, but it was always something wrong with the alarm system, not a reactor or building problem. The alarm that night seem different so they were in a hurry to get there. It was known that the reactor was shut down because the main, central control rod had been sticking and was not moving up and down properly. This made the operation of that reactor very dangerous. There was a requirement that any reactor with fuel in it had to have all the monitoring equipment (electronic data recorders, meters, etc.) always on and operating so that if any strange unexpected event occurred, the data could give a clue if not all the facts as to what happened. It was also required that a control room crew would always be on duty in the control room, even if nothing was going on. So that crew that night would be bored stiff. There would never be an assignment for the control room men to do any attempts to repair the reactor problem, especially at night.

The report was that at first only one man went inside to investigate if there was any real problem. He noted that all of the recording equipment in the control room had been turned off and nobody was in there, a forbidden action. Then he went into the reactor room and saw the two men on the floor by the exploded reactor. He was not wearing any special protective clothing and he realized that he was likely seriously contaminated with radioactive material, so he promptly went outside and was monitored by another person with a radiation meter, which showed a high level of contamination. Therefore he had to strip naked (at minus 17 degrees) and go to an outside shower facility to wash most of the rest of the contamination off of his skin. This was a very difficult task, but he succeeded. He was then taken back to the main building while others started the investigation as described on YouTube.

At first, only the two men on the floor were seen, and the third man was not seen for several hours, probably not until daylight. It was seen that both of these men had their faces impacted with many pieces of glass. When the third man was seen, it was obvious that the reactor's central main control rod had gone into his body and pinned him to the ceiling. This made it perfectly obvious that he had been standing above that control rod when the explosion occurred.

Putting these known facts together made it obvious what had happened. The top of the reactor cover had a few glass windows so that a person could look inside the reactor when needed. But it was not allowed just for curiosity. These men decided that they wanted to go and see the beautiful blue-purple colors of a nuclear reactor in water. I have seen such more than once, and it is just indescribable in its beauty. No doubt these men had heard of such a sight, so they decided to shut off the monitoring equipment to prevent their experiment from being recorded (all but an outside air monitor which really recorded very little).

Whether or not this was the first experiment, it is obvious that the one on top was pulling the control rod up while the other two were watching to see the reaction. So the control rod must have jammed just below the critical elevation. Then that person on top pulled with all his might to get it to move again. When he pulled hard enough, he raised it several inches too far! That caused an immediate nuclear reaction (much heat), not like an atomic bomb, just an extreme amount of heat in a very short time, a few thousandths of a second. That heat boiled the water making a very high powered steam explosion which blew the glass out of the viewing windows into the faces of the two men looking inside, and it ejected the control rod with such velocity that it sent the man holding it to the ceiling and pinned him there. Of course, as the control rod went out, the reactor power went much higher, causing an increase in the steam explosion's power.

The rest of the report is quite accurate. I remember watching the big rigs that went inside the reactor casing to remove the man on top and do the other work as described. — Preceding unsigned comment added by 66.31.196.155 (talk) 02:45, 9 April 2013 (UTC)


 * I am wondering if some of the assumptions you make are correct. Was there really supposed to be someone in the control room for this reactor? If so, who? This was supposed to be a maintenance procedure that they were embarking on, and only 2 of the men were qualified to do anything. As far as I have read, I don't remember anyone mentioning that the Army made control room monitoring necessary for a shutdown reactor plant. The story of SL-1 has been told and retold countless times. It's a pretty obvious question that pops up in most people's minds... Why was there no one in the control room? Nowadays, there is always someone watching the meters, and as far as I can tell, this was made a requirement or made an unbreakable rule... that the control room cannot be vacated.


 * The way I understand SL-1 is that these men were following the normal procedures and nothing forced anyone to stay inside the control room of a shutdown reactor. The main thing I can say that backs this up is the lack of personnel assigned to a night shift. Three men is a pretty small crew to be doing all of those things that night. One is a trainee. Let's say one of the qualified men has to sit inside the control room. Now suppose one man is in the bathroom or it is lunchtime. Those facilities are down the hall. So during those breaks, nothing can get down inside the reactor building because one man is watching the meters. My opinion is that the operations manager assigned only 2 qualified men to this shift because they were permitted free access to the reactor without having to sit in the control room.


 * By the way. Stop saying that one guy was impaled by a control rod. It was the #7 shield plug. I have it in the article in 5 different places. This is in Tucker's book with quote. I like to saw logs! (talk) 06:16, 9 April 2013 (UTC)


 * All of my comments are based on the reports that we received, no assumptions at all on my part. We were told all of these ideas as facts on a regular basis. Today I have no source on the requirement to always have a person in the control room whenever there was fuel in the reactor except that is what we were told. It could have been a local rule only with nothing to do with the Army or maybe only at OMRE.


 * As I wrote before, we were told that all of the real truth could not be told or the Army could not give cash donation to the families. But we were told that the main control rod was what pinned the third man to the ceiling. That is not my opinion, just what we were told. Nothing that I wrote was my opinion, it is all what I was told.  Unless there is a photograph of whatever pinned him up there while he was there, neither report can be documented as the correct one. However I believe that the official report is most likely not the correct one. Just because any part of the official report is repeated many times will never be proof that it is true or false.  — Preceding unsigned comment added by 50.146.60.100 (talk) 22:20, 10 April 2013 (UTC)


 * Well, then, you should read all of the reports listed as references to the article. They are all listed at the bottom, most of them are free to download. The original reports have "IDO" in their titles. Those reports are linked to facts described in the article. So if you read about a person being impaled not by the central rod but by a peripheral one (#7) and not the rod but essentially its sheath called the shield plug, then you can look it up. You will notice that in the IDO official reports that the central rod is inspected, that it returned to roughly the SCRAM position, and that there is no way that the central rod could have been stuck in the ceiling for a week. This also implies that the guy impaled was not the one who yanked out the central rod.


 * Your facts are all hearsay at this point, including the idea that the men were looking at pretty colors. I have also never heard of any "glass" covers on top of this reactor or any other. There is no engineering purpose for a piece of glass on top of a reactor vessel head that is torqued down to 10s or 100s of thousands of lb-ft. What type of glass can withstand that kind of torque? Were there rubber o-rings that sealed these glass panels? Can you show me a cross-section of the SL-1 plant with glass covers?


 * Your story about seeing the pretty colors is apocryphal to put it mildly. It is patently false to be blunt. You purport that these things were told to you as facts, however a cursory examination of these falsehoods reveals that the story has no leg to stand on. The nuclear power folks did quite a good job of metallurgical engineering to design reactors to be durable. Putting a glass window on a reactor vessel is the epitome of absurdity.


 * I think that the facts indicate that the operations manager was at fault, the designers were at fault, and the people writing the procedures were partially at fault. If I was a judge attributing blame, I would put the operators at 1 to 5% fault, and lay the rest of the blame upon the ones who were overseeing the design, maintenance, procedures, and personnel. The ones implementing and operating this widow maker were likely just doing their jobs. This is a tragedy in which the reactor was unsafe, the oversight (especially on the fateful night) was deplorable, and the tasks to be accomplished were potentially life-threatening. Read the article again and see if you can come to a similar conclusion. I like to saw logs! (talk) 19:01, 11 April 2013 (UTC)

New title
There appears to be a document titled "SL-1 Accident Investigations Report," of which I know of a few pictures appearing elsewhere. I am not sure if this is available by a FOIA, but here is the link to some of it: http://www.mooj.com/rxdept_page28.htm see http://www.mooj.com/images/rx-041204-SL1.jpg I like to saw logs! (talk) 17:13, 5 November 2013 (UTC)
 * Cool, thanks!

Reactor configuration
The T and cross shaped control/fuel rods, are these vertical in the reactor core? It is hard to visualise from the description. Why are they this shape Vs just straight control rods? Tttonyyy (talk) 11:51, 12 January 2020 (UTC)

Without sufficient moderator, cores such as SL-1 would be unable to sustain a nuclear chain reaction.
The article says: Without sufficient moderator, cores such as SL-1 would be unable to sustain a nuclear chain reaction. Note that this has over 93% enrichment, which can easily sustain a reaction without moderator. But yes, at low enrichment moderators are needed. Gah4 (talk) 09:15, 26 May 2023 (UTC)
 * Wrong. The design of the reactor fuel plates did not allow enough reactivity in anyplace to sustain a nuclear chain reaction without moderation. This is true of every nuclear reactor ever designed that needs a moderator. Examples of reactors that need no moderator exist, such as the fast reactors used in the Kosmos satellites, e.g. Kosmos 954. A moderated reactor, however, cannot magically convert itself to a fast fission reactor when the moderator is absent. It simply won't work and is considered shutdown and safe when the moderator is removed. SL-1 is one such reactor in which the moderator was expelled during the accident, making it intrinsically safe as long as rain (or some other water) did not enter the core. I like to saw logs! (talk) 20:45, 14 April 2024 (UTC)
 * It seems that the critical mass of U235 with a good (I am not sure how good) reflector is about 15kg, so 14kg is close, but maybe not close enough. Even so, I would be careful around 14kg of U235! I don't know about the reflectivity of any nearby materials. Gah4 (talk) 22:49, 15 April 2024 (UTC)
 * Reflectors are generally used with moderated neutrons, however. It seems that you are not very knowledgeable about reactor design. Anything that reduces neutron leakage can be considered a reflector, with water being a common one. Tungsten Carbide is a reflector of fast neutrons, but is uncommon. The SL-1 core can be considered an example in which water is the primary reflector, and thus moderated neutrons are the primary ones being reflected. Let's think about this core in particular. Any of the original reflectors that were designed in were made pretty useless when they decided to operate with a smaller fuel loading, causing the distance to them to increase by several centimeters - except the reflections done by water.
 * Regardless, after the loss of water in the area of the core, the neutrons essentially fly away without a chain reaction. The shutdown margin was very large. Thankfully, it was a small core and apparently not a lot of melting occurred (20% or so), and so the vessel remained intact before they drilled a massive hole in it to look inside. The only appreciable heat was from decay. Sure, it may have been several kilowatts of heat, but the melting didn't bring enough of the fuel together to be critical. There would have been considerable amounts of aluminum mixed in with it. The only thing left to reflect the neutrons was the steel and gravel. Because the neutrons were fast, the U-235 was unable to sustain the reaction. I like to saw logs! (talk) 09:37, 28 April 2024 (UTC)
 * Reflectors are generally used with moderated neutrons, however. It seems that you are not very knowledgeable about reactor design. Anything that reduces neutron leakage can be considered a reflector, with water being a common one. Tungsten Carbide is a reflector of fast neutrons, but is uncommon. The SL-1 core can be considered an example in which water is the primary reflector, and thus moderated neutrons are the primary ones being reflected. Let's think about this core in particular. Any of the original reflectors that were designed in were made pretty useless when they decided to operate with a smaller fuel loading, causing the distance to them to increase by several centimeters - except the reflections done by water.
 * Regardless, after the loss of water in the area of the core, the neutrons essentially fly away without a chain reaction. The shutdown margin was very large. Thankfully, it was a small core and apparently not a lot of melting occurred (20% or so), and so the vessel remained intact before they drilled a massive hole in it to look inside. The only appreciable heat was from decay. Sure, it may have been several kilowatts of heat, but the melting didn't bring enough of the fuel together to be critical. There would have been considerable amounts of aluminum mixed in with it. The only thing left to reflect the neutrons was the steel and gravel. Because the neutrons were fast, the U-235 was unable to sustain the reaction. I like to saw logs! (talk) 09:37, 28 April 2024 (UTC)

Not a meltdown
This core did not melt down. Using the term "meltdown" is completely erroneous, since it was destroyed by mechanical explosion. i.e. "catastrophic disassembly." I have kept a single incidence of the erroneous term at the top of the article, primarily due to its use as a non-technical description of a nuclear reactor that overheats and is destroyed from its own heat. It probably should have scare quotes, as it is a so-called "meltdown." As the article states, corium was not found in it. I like to saw logs! (talk) 18:32, 14 April 2024 (UTC)

abnormally large reactivity worth
Can abnormally large reactivity worth be made to sound better. The worth seems especially strange here. Gah4 (talk) 22:46, 15 April 2024 (UTC)