tv Oral Histories Manhattan Project Engineer Roger Rohrbacher CSPAN February 21, 2021 3:10pm-3:49pm EST
was an instrument engineer for the manhattan project at the b reactor. he was responsible for measuring neutron flow and monitoring radiation levels. in an interview, he explains how the reactor worked and describes the challenges they face in the early stages of the development. the voices is a manhattan project oral history collection was created by the atomic heritage foundation and is managed by the national museum of nuclear science and history. >> 1942 and 1943, i was working for dupont and a plant in illinois. i bodies were disappearing and they ended up in richmond. i got the map out and richmond was not even on the map. i contacted them, but you guys doing? under the guy interrupted, he said, we sure does something out
here. a couple weeks later, my boss said, i would like to talk to you about a new job. i was young and single, i said, i will take it, assuming i would end up in richmond. they sit, report to dr. so-and-so at the university of chicago 40 miles away. this was part of the manhattan project. i was assigned to an engineering development group and we were dipping samples of aluminum in water, checking for corrosion. i found out somebody had shipped 5000 gallons of river water to the university of chicago and this is what we were doing. these were the process tubes and material for the fuel. i came out here and ended up in pascoe at 4:00 a.m. or something like that. my buddy was supposed to meet me. he did not show up.
i made a mental note, this guy better have a good excuse. turned out he was in the hospital, appendicitis, they were in surgery that morning. so we let him go. i ended up in the quarters for a couple days then moved into a dormitory. i presumed i would be doing some chemical work, but during the interview, a fellow said, we would like to have you in the instrument department. i almost said, i play trumpet, i will fit right in. he says, what you know about instruments? i said, nothing. he said, we are given -- we are going to give you hands-on training. in a year, you will know everything you need to know. not quite true. i ended up mostly in dd&f.
i came out in april of 1944, worked on his mentation, mostly flow and temperature and pressure, and later, radiation monitoring. that was one of the clues of what was going on. none of us really knew except maybe a dozen or so scientists. something came up eight months after start up and we had some problems with the chambers monitoring neutrons. the foreman said, move this neutron chamber a couple inches. i had a full year of physics, this is no chemical -- that was the story, chemical fire. i was in training for a while, worked in the reactor building, concerned with the equipment to measure the neutrons and pressure and so forth. each process to had a flow
monitoring device and the exit of each tube had a thermometer to measure temperature. this is part of dupont's program. one of the main concerns in the reactor is it had a good cooling at all times and by monitoring the flow, that give you a clue. if that did not respond properly, you had a temperature measurement on the outside. if it got too hot, you were in trouble. that was one of the problems. everything had a failsafe. they were all in series. one bulb goes, they all go. they hauled -- they called this a scram. their safety equipment was a rope on a safety rod leading
down to a post. there was a man standing there with an ax. if trouble came up, he was supposed to chop the rope. they called him safety control rod axman. whether it was used or not, i don't know. that term came to use for any unexpected scram and there were a lot of reasons for doing that. one of the things that came up was how do you measure a small amount of current? a mirror suspended on a fine thread and magnets on the site and coils and a small electric current from the chambers moved this mirror. this equipment was pre-world war ii stuff.
that detected a small amount of current. there were a lot of other features in the reactor to monitor for what was going on and if anything failed, it's grant. -- it was scrammed. they were control laws that were electronically driven and another system provided hydraulic force. the operator would pull out these rods and monitor the reactor. the power level generally measured in how fast it takes to get from one particular power level to another. the operator was careful during start up muttering the operating when everything was normal, it was quite simple, relatively speaking. it is like a car in cruise
control. if you have no traffic and don't need to stop, you just sit there. the operator sat for two hours at a time in the control room. when other operator was reading other gauges and so forth. -- one other operator was reading other gauges and so forth. then, if minor adjustments had to be made, he would move one control rod a half inch at a time. when there was trouble, these horizontal control rods would go in the reactor and denied vertical safety rods would drop in the reactor and that was automatic. and rico came out at one time when they were testing these rods and he was concerned that there were testing so much that they knocked to the bottom out of the tubes in which they were contained.
he said, you ought to put a spring at the bottom or somehow reduce it. that information has now been declassified. his codename was eugene former. -- eugene farmer. he was reasonably happy but did not like our testing program. kind of interesting. one other problem with the early days before computers, gauges that were 2004, all the ratings had to be taken once a shift and in a similar matter, they monitor the temperature, had to be recorded twice a shift. a tremendous amount of work. some people came up with a deal to avoid this. they went to typewriter people and they said it is impossible when you want to do.
well, send us a typewriter anyway. two typewriters came out and their names were removed. they did not want to have any part in a failed operation. it turned out, it worked. this could automatically monitor all the process tubes and record the temperatures on a sheet of paper. that was a real improvement. we had some problems with the reactor along the way. one was graphite expansion. the graphite expended to the point where the tools could not pass the process tubes. the first solution was to make four inch instead of eight inch, then they were looking for a permanent solution. they decided if they could get the graphite hotter, it would
reduce this growth. so they mixed the gas, in the reactor it was helium. they mixed that half-and-half with carbon dioxide. that caused the graphite to heat up in that heating apparently stopped the growth and may reduced it a little bit. so that was an interesting facet. another problem was fuel ruptures. there is not good bonding between the metallic uranium and its jacket. you get a little water inside and a reaction between the water and they uranium when pulled out the fuel and it would stick. if it got bad enough, you cannot get it out by pushing on it. sometimes the whole process to pad to be removed. -- processed tube had to be removed. one of the problems was, did you
have a problem that needs to be shut down or do we not? generally, they tended to wait until they knew they had a problem. >> how many times did they have to scram the reactor? roger: in the early times, maybe a couple times a week. sometimes it got so bad >> she was talking at the same time. start again within the early days. roger: the early days, the reactor scrammed often, sometimes a couple times a week. most of the time, it was due to the gauges getting a little off scale and when one of those things happened, it would scrammed the reactor. there was a feeling that we can do away with these gauges and they try to that for a few months. then they said, this is not too
bright i think to do, so they put it back in and they got a deal to rearrange the system so that it operated better. one of the problems, more water flowed to the center than the outside. there are three or four zones and each gauge headed to be almost individually set. in the early days, the setting had to be done behind the panel. after a couple years, they decided to move the adjustment knob to the front. that helped a lot in that regard. >> you work for dupont before you came to hanford. what made dupont a good choice for this project? roger: dupont was known for construction of plants and for chemical plants and so forth. they were noted for a couple things. one was their safety aspects,
and other thing they called contingency. i had never heard that term used in a plant. our group wanted a tank. the designer said, what size tank do you want? 4,000 gallons ought to do it. he said, what is your contingency? i don't have any, that is what we need. ok, we will put in a 4500 gallon tank. this is a story with general groves, the story was enrico said 1500 was sufficient for the reactor. he goes to general groves and says, what is your contingency? 1500. something went wrong with this plant.
the general is a pretty sharp guy, he says, how many more tubes do you want? he says, 500. so they put in 500 tubes. without that, the reactor probably would not operate. in the early days, while the reactors were given only a 56% chance of operating, which opened up another questions. how come there is no a reactor? in the early days of chicago, the plan was to build eight reactors and they had some concerns. how do you contain helium and how do you do this and so forth? so they changed their view. we will build three water cooler reactors and that will be the same process. if you had any questions -- if
they have eight sites lined off, how far apart should these reactors be for safety? he says, five to 10 miles apart. we are expecting something to the nearest foot and he came up with five miles variation. >> what about -- getting back to the problem, which is what this is the today the use of the rods that were designed as an afterthought. could you explain what that problem was and why the extra rods, the extra capacity solve that problem? roger: this whole project, manhattan project, was going full speed. all the answers were not known and when the b reactor first started up, things went quite smoothly. you cite pulling out the control
rods and the power level went up. all of a sudden, over a period of time, if he pulled the rods out, the power level kept going down. at this time, they were concerned with what is going on. i will have to tell you about security. this area was top-secret. secret, rather. the big boys and superintendents had top-secret clearance and a room next to this was a top-secret room and they were talking away. one talked to his boss, he said, go by the door, see what those guys are doing. the superintendent comes back,
he says, you wouldn't believe it. they are setting up a pool to guess when the reactor would start and the winner will get a bottle of wine. it was an earthshaking event, will the reactor work or not? during the reaction, iodine decayed to xenon and the xenon was a neutron absorber. the process by which xenon regenerated, it absorbed the neutrons and shut down. one of the ways they made it work was an additional 500 tubes provided more neutrons so you can start up again, but you could not necessarily start up right away. normally, you have to wait for the xenon to decay and it has a fairly short half-life, maybe 20, 30 hours. you usually wait a day and start up. if they knew when the scram
occurred, what the problem was, they had a quick start up, they could start up within 20 minutes. put the rods in where they were and hope everything was ok. later on, i would guess early 1950's, enriched fuel was used which had more uranium and more neutrons were available. that halfway got rid of the problem. >> let me see if i can get this right. even though you had more neutrons for the startup, you still had xenon, so the extra neutrons would overpower the xenon until it decayed sufficiently? roger: to start up? when you first started, there was no xenon. as the reactor started to operate, xenon was built up. as you build up a xenon, the
xenon absorbed neutrons so the neutrons were not hitting more uranium and generating more neutrons and so forth. by providing additional fuel elements, more uranium, it overcame that. there were still restrictions, but that was generally the problem. it was solved with enriched fuel that had more uranium, where the neutrons came from. >> at some point, they would not go for just software engineers. could you give a good description of what this reactor is say to a layperson who does not know what this reactor really dead? a simple description of what it does? roger: the core of the reactor is a big tube of graphite.
graphite is like charcoal, carbon. it is a 35 foot two. -- tube. the neutrons come from the uranium. the uranium is radioactive and it has two parts. uranium to hunt a 35, which generates neutrons -- uranium 235, which generates neutrons, and uranium 238, which does not generate neutrons. the neutrons are reducing energy and hit the uranium 238 and that process is called transmuting, transmute uranium into plutonium. in this process, a lot of other products are also formed. maybe 12, 15 other products. isotopes, cobalt, and so forth.
the only one of concern was plutonium. another concern with the reactor , after you make plutonium, it took 2.5 days for the process from uranium 238 to plutonium 239. the reaction does not stop then and the uranium 239 conversed to plutonium 240, which is not weapons grade. you can probably use it, but why not use diesel fuel and fertilizer? it is not that great. during the operation, the reactor was shut down every month and essential process tubes were discharged to get the maximum 239. the intermediate tubes would probably be discharged five or six months. that way, they got the maximum plutonium 239.
that was about the time computers were coming into being. when jobs was -- one job was went to discharge at what period of time based on the neutron flux. how active was the reactor and so forth. that was monitored by the temperature rise and this was a top-secret thing. a special man did this every day and he kept the drawer top safe -- top-secret. that was used to determine the maximum plutonium 239. that was another process, discharging the fuel. the reactor had to be shut down that you had to keep a small amount of water flowing. it pushed out the charge of metallic uranium. that dropped into a pool of water. it dropped to the air for about
20, 30 feet, then into 20 feet of water. it is put into what is called a mattress pad, which was rubber or plastic, and the fuel elements, they were eight inches long. if they dropped onto concrete, they would break, so this mattress pad stopped it. except the radiation was so terrific that the mattress pad got brittle and the fuel elements would fall through. there had to be strict accounting for all of this, searching all over the base to find them. the ones behind or underneath the mattress pads, they cannot really get to. they turned out the lights and the glow showed through so you could get tongs and put them in there. this is another great concern for the security man.
the buckets were loaded -- the bottom was laid in all horizontal. the second, they did right angles. they did 64 fuel elements in a bucket. to confirm that the count was right, they waited the bucket -- weighed the bucket. one great concern by the atomic energy commission what to account for every fuel element. that was tough to do. thousands of these things. 64,000 fuel elements in a reactor and you discharge a third. however, quite often, it would be short or long a fuel element. there was a secret hiding place.
an operator said, one time we were so sure, we had to steal from another guy's secret supply. what can you do it fuel elements? pick up a fuel element, you get a lethal dose and 15, 20 seconds. even after the reactor deactivated, i think they found a few along the way. >> where where they stored? where did they store these? roger: hidden in some corner someplace, maybe a bucket that said do not use or something like that. of course, another problem was, occasionally, there would be a mistake. to discharge a process tube, you had to take off the cap, front, and back and push the fuel out by putting a new fuel. they somehow got the cap off the front of one tube and the cap
off the back of the adjacent tube and guys were pushing and pushing. they said, what is going on? they pushed so hard that part of the thing next to the nozzle, it started to come out of the reactor. we said, we've got a problem here. there are other problems that fuel elements would get stuck on the elevator. this was another interesting thing. the operators got a fair amount of radiation. they sent to the supervisor or engineer to take care of the problems. one engineer, he told me they got an element stuck on an elevator and they gave him an eight foot pole and said, you try to dislodge the fuel. try twice. whether you get it or not, get out of there.
he got it the first time and he was running backwards so fast, he ran over the radiation monitor that was monitoring his radiation. >> let's see. >> you were telling some stories about what people had said about what was going on out here. roger: a lot of rumors. everything coming in, nothing going out. some people said, this is a sandpaper factory. another one, it was fdr's winter palace, he is going to convert one of the reactor buildings. we did not know it was a reactor building at that time. another one, a show until school, a kid says, i know what they are making, they are making toilet paper. my dad brings home two balls a day.
-- rolls a day. people left with a bunch of copper wire. they said, step over here, please. we never saw the guy again. another story, horses' front ends. what he going to do with those? send them to washington, d.c. and connect them up. >> i am losing control here. i'm trying to remember what else we need. >> you have given us a lot of material. >> tell us about the people here. was there pride in the work? what were the people like? these guys were pioneers and they knew it and they had a sense of it.
did people have a sense of what they were doing and how important it was? roger: people were dedicated and most of them in the early days came from other dupont plants. even though they did not know what they were doing, they did what they were supposed to. i think there is a common feeling that we are doing this and so forth. the thing that surprised me, after a few security lectures, you never talked about it. you go to a movie and there would be big letters, silence means security. security meetings, it was supposed to be half an hour long, it would be longer and longer. we convinced the security people to have meetings at 11:30. 12:00, we would all rattle our tin lunch buckets and the security guy got the message.
the fbi checked us ahead of time. my mother called me up and said -- this is back in st. paul -- roger, what are you doing? they are asking all about you. of course, we did get a bunch of security devices. we did not really get told what we were doing, though we got the impression -- never pretty good stories. when operator was hefting one of these fuel elements. he said, i used to work in british colombia and this fuel is just as heavy as uranium. bill says, that is interesting. he did not want to spill the beans. nothing really was said. what are you doing here? you had a few pounds of stuff and he got an inkling, but not until the newspaper came out and said it is the bomb.
matter of fact, a reporter from the tv station in seattle interviewed a bunch of us. she said, well, that would not be the same today. i said -- i think there was a different energy. they never talked about it. volleyball, it dehydrates a guy, you have to go to a tavern and drink water, get your liquids back. but no one ever said he word. -- said a word. >> maybe you did not even know it was uranium coming out of these reactors. roger: that is true. most of the people did not know. there was probably a dozen in the early days and maybe three
or four dozen later on. the people who operated the reactors had no clue what was going on. i would say that is probably true. even myself, i had pretty good suspicions. we did not know for sure that this was going to end up in an item bomb. we knew physics and uranium was involved. that was about it. just got the stuff through osmosis, no one ever said. >> some of the guys at the manhattan project in most alamosa said they were only told certain things. but like you say, through osmosis, people figured it out. was it easy to figure out? was a still difficult? roger: i don't think any of my acquaintances figured it out. >> i'm summit, to be a favor.
-- i'm sorry, do me a favor. say figured out that we were working out material for a bomb. go ahead. roger: i was under the impression that most people did not realize that what they were doing would end up in the atomic bomb. i think they were just guessing along the way, you got the impression of something, other than a chemical plant and anything else, and it had something to do with physics. the operators themselves, they were operating the plant based on neutron production. they had some clue. people irked -- people worked in other areas, separated plutonium from the other stuff, nor could they go in the laboratory or where the fuel production was made. only with a good excuse to find
out some particular problem related to the reactor. in my case, i wanted to know something about i could go some other place, but nobody ever talked about what they were doing. it was quite interesting. >> whatever you're doing with your hands, it is making a squeak. you are rubbing their hands on the bottom of the chair. roger: you can hear that? >> it is a pretty sensitive microphone. anybody else have anything? >> when you found out it was a bomb, what was your reaction? roger: when the official news came out that it is the bomb, it is kind of a surprise and relief. well, i suspected something like that. but i think most of us did not. then we got all the stories
about, didn't you know what they were doing? they were sticky stuff in a reactor. -- yeah, they were sticking stuff in a reactor. maybe 95% did not know it would end up as an item bomb -- atom bomb. >> how did attitudes change the next day you came back after you knew what had happened? roger: i don't remember any particular change in the people after they knew it was an atom bomb and they were making plutonium for that reason. come to think of it, there was some information out prior to the announcement that talked about how much product was being made. all these tons of uranium they were coming out with, tons of this stuff, what is going on?
i think the answer is it probably did not change their attitude much. abor was still going on -- a war was still going on, they build more reactors. -- built more reactors. b was shut down for six months. then there was a replacement for d reactor called dr. then they built a replacement for f reactor called h. about twice the size of the original reactor. later was n reactor.
that is where we ended up, working reactor design and in the instrument group concerned with safety aspects. it was a rhode island ability -- it was a reliability analysis group, what might fail how often and what could be done about it. interesting results came up. nothing was wrong with a simple system. what if this valve does not open? we'll put on a second valve operator. it got so, the most reliable thing was to have a simple system with a manual override. if i guy -- if a guy really wanted to open a valve, he could push a button.
this is the days when computers were just getting to be. we had this big thing, something that could cause damage to the reactor. 32,000 inputs would cause the reactors problems. the computer at this time was so skinny, they had to divide the program into two parts. this is also the days of big boxes of cards shipped to seattle and ship the stuff back with the answer. we called them girls, even though one was 65, they would do as much about the programs as we would be ready -- as we would.
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