A Practical Guide on how to Training With a Running Powermeter
There is no denying that trends of training fluctuate over time while major tenets in training remain stable. Pace, distance, and heart rate are relatively consistent metrics that most runners are familiar with. The technology to interpret these values has evolved over time and the metrics associated with these training tenets allow runners to reach higher performance levels once they adapt to using these tools.
As technology continues to increase, new concepts emerge with much promise. Some technology requires users to invest a bit of time and effort into learning how to use interfaces and technological setup with the payoff in improvement after they adapt to their new-found gadget.
Simplicity in presentation and promise of improvement is what every brand would like to offer athletes keen on setting new PRs and making that next leap in performance level. One of these newer technological concepts, specifically in long distance running is power. Power
is displayed as a standardized metric called Watts
. Most running power meters come in the form of a foot pod that clips on to some part of the shoe with the shoelaces being the primary spot secure the foot pod. Measuring from the foot allows for the capture of the entire running gait and improves distance and pace accuracy.
My goal of this post is to simplify the practicality of training with a running power meter and why adding in a simple tool can improve the planning, racing, and analysis of your running. Full disclosure: I work at a company called Stryd that makes a running power meter. This is no way an advertisement, rather an informational post on the concept of training with power. To start things off I'm going to answer some questions that some other ARTC people asked the other day:
I think I push too hard on uphills. I assume a power meter could help me with this? Yes. When you run up a hill during a race (especially) or normal training run your effort will increase instantly while your pace slows. Heart rate is a metric that can be used to gauge effort a bit better than pace, but heart rate lags in response to your power output. Power is a way to maintain effort in real time and not sacrifice performance on hills and what comes after in a race.
Can it please include a brief ELI5 "this is what "power" means, and this is what you can do with the data and what it means for your running" To break it down with the most simple explanation possible:
Power is a representation of how hard you are working at the moment and represents a better training metric than the standard pace and distance tracking.
With the biomechanical data that is tracked, you can have a better eye on your physical running ability and notice personal trends over time. Power means more consistency with training and can help a runner prevent overreaching during training.
Does running economy improve power? Running economy is a slightly tricky thing to define when outside of a lab. Running power meters can give an equivalent metric for non-lab test environments. When looking at power related to economy, Running Effectiveness (RE) is typically measured. This equation is meters per second, divided by watts per kilogram. A “good” RE is over 1.00, with elites being around 1.05.
Personally, I think RE can be used when comparing efforts across a training block when looking at efforts run on the same surface. For instance, you run 4 x 400 on a track at the beginning of a training block. Your pace is 1:30 average for each rep, and the average for your watts is 309. The RE average is 1.006.
You repeat this workout later in the season and in this second case, your average is 1 second faster per rep but your power is 3w lower. You lost 1kg over the training cycle and your W/kg is slightly higher. Your RE is 1.01 this session which shows your running effectiveness has improved. Running effectiveness improving means you don’t have to output as high of power to maintain that pace.
It might be a stupid question but I'm curious how it works with head/tailwinds, presumably a steady run into a headwind would require more power, but I don't really see how a running power meter would measure that, can you see a decent amount of variation depending on wind gusts or head/tailwinds? Not a stupid question! Currently, that is the limitation of all running power meters. A strong gust or steady wind does call for a higher output, and that is the next logical step to tackle for running power meters.
How does a running power meter compare to a cycling power meter? Good question! Bike power meters are usually on the pedal/gear and measure mechanical forces applied. I can only speak about Stryd specifically, but Stryd uses an algorithm and the motion of the foot through 3D space to give running power.
The Basics You might have questions about what is actually being recorded during your run, and how you can track these different metrics. Here goes the list:
Power - Power is displayed in Watts (per second). I personally like to compare Watts per kilogram in case weight changes while training. Here is a distribution of W/kg for 1 Hour Power:
Form Power - When you run not all power is dedicated to moving forward. As much as we would like to think that we are perfectly efficient, individual form and inefficiencies impact how much power is being expended aside from forward motion. Form power is that number that is not being used to move forward.
|Level ||Females ||Males |
|World Record ||5.7 ||6.4 |
|International ||5.1 ||5.8 |
|National ||4.6 ||5.1 |
|Regional ||4.0 ||4.5 |
|Tourist ||3.4 ||3.8 |
|Fair ||2.8 ||3.2 |
|Untrained ||2.3 ||2.6 |
Form Power Ratio - Is the metric to look at when analyzing form power. The idea is that you want your Form Power to either remain the same or go down as your overall Power increases. The trend is the important thing to look at.
For comparing across flat terrain:
Cadence - This is a relatively simply explained metric. The number of times the same foot hits the ground. Some people like RPM (rotations per minute, or that one foot being tracked) or SPM (total steps per minute). Cadence can be reported via accelerometers in a watch but foot tracking is always more accurate.
|Form Power Ratio ||Distribution |
|>25% ||Below Average |
|23-25% ||Average |
|<23% ||Above Average |
|<20% ||Very Good |
Ground Contact Time - The time in milliseconds or ms that the foot is spending on the ground. This is a metric that goes along with cadence and some of the other biomechanical metrics. My suggestion is to feel out your own personal ground contact time in the post run analysis and see if you are on the low end. If so, adding in specific plyometrics can help with efficiency.
Vertical Oscillation - This is the measure in centimeters or cm that the center of mass of the body moves up and down. Typical ranges are 5-9cm. Vertical oscillation will decrease when running uphill.
Leg Spring Stiffness - This is probably my favorite unique metric to track. Leg spring stiffness is the measure of the elastic forces in the lower leg, such as the Achilles and other tendons and ligaments/fascia. LSS divided by weight in kg allows for comparison across runners. The change in LSS over a run can be a signal for fatigue. The better a runner is, generally the more resistant they are to fatigue and their LSS/kg drops less during a race.
|Rating ||Value |
|Very Good ||.173 |
|Above Average ||.158 |
|Average ||.143 |
|Below Average ||.128 |
|Very Below Average ||.113 |
Incorporating Power into a Training Plan Let’s say you are in the possession of a running power meter. Now how do you actually use it? I will assume the device is paired with a watch and you can see power live during your run and that you have a setup to review data after the run as well.
My first suggestion is to run like normal for 1-2 weeks to start to build up a base of data to look at. There isn’t much use in watching a number on your watch screen the first week except to see how your power changes on different surfaces or as you run up and down hills.
Once you have a few runs the next step is to get familiar with power zones. There are a few different methods behind this
The most important number to look at once you’ve established this curve is your Functional Threshold Power, or FTP. Stryd refers to this as “Critical Power” so I will refer to it as CP. This is the power you can sustain for 1 hour and is fundamental to establishing other ranges.
- The easiest is to run a race wearing a power meter, typically a 5k or 10k. You’ll get your power average for the race and your time and input it into a calculator. You’ll then get what is called a power duration curve based on the estimate from your race.
- The second method is a little bit more strenuous but very valuable. A Critical Power Test can be used to add another data point to your power duration curve and give a better idea on how you perform at longer versus shorter distances. The most optimal test procedure is to run a 2400m time trial, walk/jog 20 to 30 minutes, then run a 1200m time trial. These efforts (with their time and power) are input into a calculator and fit along your curve to give a more accurate depiction of your running performance.
Looking at Zones These practical zones come from coach Steve Palladino and lay out a foundation to base completely individualized training off of. Again, all of these will be based on the CP. For an example, let’s say a runner has an CP of 300w.
1A Post Interval Recovery: Easy recovery between intervals and cool-down - 50-65% of FTP / CP
1B EZ Warm-Up: Easy warm-up component before intervals or racing - 65-75% of FTP / CP
1C EZ Aerobic Running: Easy Aerobic Runs 75-80% of FTP / CP
Endurance / Long Run: Typically, average power for long runs / overdistance (or sustained runs with higher intensity mixed in) Otherwise a grey zone for more standard lengthen aerobic runs. 81 to 87% of FTP / CP
3A Extensive Threshold Stimulus: Sweet spot running. Tempo runs. Generally, sustained effort runs executed at the lower percentages of FTP, or, long (>=15 minute) intervals at the higher percentages of FTP within this zone. 88-94% of FTP / CP
3B Intensive Threshold Stimulus: Threshold work. Longer intervals and occasionally, sustained effort running - 95-101% of FTP / CP
Supra Threshold: Suprathreshold work. Generally intervals - 102-105% of FTP / CP
Maximal Aerobic Power Stimulus: Max aerobic work. Typically intervals (or occasional ‘time’ trials) - 106%-116% of FTP / CP
Anaerobic Power Stimulus: Anaerobic work. Short intervals or short time trials - 117-150% of FTP / CP
Sprint / Maximal Power - Maximal Power. Sprints. - >150% of FTP / CP
So now you have all the number and math behind you. How do you put it in to use to help your running?
The goal of an easy or recovery run is to maintain fitness and not overcook yourself for the next quality workout or next run coming up. Pace does not matter and should not matter. You can run varying terrain at the same exact pace but exhaust yourself for an important workout because you were glued to hitting an arbitrary time it takes to complete a set 1k or 1mi distance.
If a recovery effort for a runner is usually 8:00-mile pace on flat terrain, but they go run a rolling course with 500ft elevation gain at 8:00-mile pace, this is obviously more stressful than a flat run. When you focus on running a specific recovery power you gain the ability to monitor recovery with a better understanding of the stress put on your body.
Running easy runs or recovery runs at 65-80% of your CP ensures you are recovering and ready to go for the next planned workout or run. Our example runner targets a wattage of 195 to 240 on easy runs.
Let’s look at some workouts now and give some examples on how to structure sessions to be consistent, maintainable, and specific to current fitness and running goals. Here is an example workout for a runner looking to target a mile race at the end of the season, but also working on their Threshold at the beginning of the season. They just did a CP test so they know their CP is 300 watts, and their goal for the mile race is 350 watts. :
This workout lets them get some extremely specific running at the end goal mile power, while still training an extremely specific threshold power based on their current fitness. They can then build off of this based on their training plan and not worry about guessing if they are actually in a certain type of shape or not. Another example I’d like to give is an early (or late) season workout involving hills
- 15 minutes warm up at 65-75% of CP - 195 to 225 watts
- 20 minutes at 98-102% of CP - 294 to 306 watts
- 5 minutes at 50-65% of CP - 150 to 195 watts
- 4 x 1 minute at goal mile power - 350w
This same runner is now in the latter part of their season and is looking to do 8 x 200 at mile power on the track to sharpen up before their big race. They do an easy 15 minute warm up but find the track is currently being used for a middle school soccer game and can’t be accessed.
Rather than ditch their workout they continue a short jog over to a hill where they can translate this exact workout and not worry about pace, rather just worry about the effort needed to accomplish the goal.
The runner then subs out the workout as 8 x 40s hills at 350w. The runner averages 348w and knows the same stress is applied to the body and that they got their last tune-up workout in without any hiccups despite logistical circumstances being against them.
Our example runner is now training for their road racing season during the summer. They set out to do a 15 mile run with the first seven as a warmup, six miles as a progression from Marathon wattage down to CP wattage, then two miles cool down.
Their structure looks specifically like this:
The course that our runner ran on had a very large uphill in the third mile and the pace drops 20 seconds for that mile. The wattage, however, remained consistent and they were able to finish exactly with the effort intended instead of burning themselves up too early in the run. On race they won’t worry about maintaining a harder effort at the same pace up a large hill, they’ll pace themselves with an even steady effort and make sure all their hard work is realized when they cross the finish line.
- 7 miles at 65-75% of CP - 195 to 225 watts
- 6 miles starting from 90% of CP to 100% of CP - 270 to 300 watts
- 2 miles at 65-75% of CP - 195 to 225 watts
The half marathon is here and based on a recent CP test the runner thinks they can now run at 305w over the course of the half marathon. They set their watch to a 10-second watt average and set alerts when they go above 310w and when they go below 295w. They end up pacing perfectly based on effort and finish with a 1 minute PR and have averaged 307w!
Our runner wants to learn a little bit more about their race and see where they might’ve been able to improve even more. The power looks extremely consistent with their lowest mile average being 298w and highest being 312w. They notice that their cadence dropped a few steps per minute in the middle of the race and their vertical oscillation increased a few tenths of a centimeter. Their form power ratio dropped slightly during this section as well. They were overstriding in the middle and they were a little less efficient than they could have been. Now they know to keep it in mind for the next tempo run or longer race.
So that's what I have for a brief introduction to the practicality of training with a running power meter. Is it for everyone? No. Is it for people wanting to improve? Sure. I think the potential to improve your running with a power meter is immense and the technology is only improving day to day.
I'm sure there will be some. Feel free to leave them in the comments to discuss, or shoot me a PM if you want to ask privately!
submitted by CatzerzMcGee
The manhattan project thing 2/5
Patterson approved the acquisition of the site on 25 November 1942, authorizing $440,000 for the purchase of the site of 54,000 acres (22,000 ha), all but 8,900 acres (3,600 ha) of which were already owned by the Federal Government. Secretary of Agriculture Claude R. Wickard granted use of some 45,100 acres (18,300 ha) of United States Forest Service land to the War Department "for so long as the military necessity continues". The need for land, for a new road, and later for a right of way for a 25-mile (40 km) power line, eventually brought wartime land purchases to 45,737 acres (18,509.1 ha), but only $414,971 was spent. Construction was contracted to the M. M. Sundt Company of Tucson, Arizona, with Willard C. Kruger and Associates of Santa Fe, New Mexico, as architect and engineer. Work commenced in December 1942. Groves initially allocated $300,000 for construction, three times Oppenheimer's estimate, with a planned completion date of 15 March 1943. It soon became clear that the scope of Project Y was greater than expected, and by the time Sundt finished on 30 November 1943, over $7 million had been spent.
Map of Los Alamos site, New Mexico, 1943–45
Because it was secret, Los Alamos was referred to as "Site Y" or "the Hill". Birth certificates of babies born in Los Alamos during the war listed their place of birth as PO Box 1663 in Santa Fe. Initially Los Alamos was to have been a military laboratory with Oppenheimer and other researchers commissioned into the Army. Oppenheimer went so far as to order himself a lieutenant colonel's uniform, but two key physicists, Robert Bacher and Isidor Rabi, balked at the idea. Conant, Groves and Oppenheimer then devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department.
Main article: Metallurgical Laboratory
An Army-OSRD council on 25 June 1942 decided to build a pilot plant for plutonium production in Red Gate Woods southwest of Chicago. In July, Nichols arranged for a lease of 1,025 acres (415 ha) from the Cook County Forest Preserve District, and Captain James F. Grafton was appointed Chicago area engineer. It soon became apparent that the scale of operations was too great for the area, and it was decided to build the plant at Oak Ridge, and keep a research and testing facility in Chicago.
Delays in establishing the plant in Red Gate Woods led Compton to authorize the Metallurgical Laboratory to construct the first nuclear reactor beneath the bleachers of Stagg Field at the University of Chicago. The reactor required an enormous amount of graphite blocks and uranium pellets. At the time, there was a limited source of pure uranium. Frank Spedding of Iowa State University were able to produce only two short tons of pure uranium. Additional three short tons of uranium metal was supplied by Westinghouse Lamp Plant which was produced in a rush with makeshift process. A large square balloon was constructed by Goodyear Tire to encase the reactor. On 2 December 1942, a team led by Enrico Fermi initiated the first artificial[note 3] self-sustaining nuclear chain reaction in an experimental reactor known as Chicago Pile-1. The point at which a reaction becomes self-sustaining became known as "going critical". Compton reported the success to Conant in Washington, D.C., by a coded phone call, saying, "The Italian navigator [Fermi] has just landed in the new world."[note 4]
In January 1943, Grafton's successor, Major Arthur V. Peterson, ordered Chicago Pile-1 dismantled and reassembled at Red Gate Woods, as he regarded the operation of a reactor as too hazardous for a densely populated area. At the Argonne site, Chicago Pile-3, the first heavy water reactor, went critical on 15 May 1944. After the war, the operations that remained at Red Gate moved to the new site of the Argonne National Laboratory about 6 miles (9.7 km) away.
Main article: Hanford Site
By December 1942 there were concerns that even Oak Ridge was too close to a major population center (Knoxville) in the unlikely event of a major nuclear accident. Groves recruited DuPont in November 1942 to be the prime contractor for the construction of the plutonium production complex. DuPont was offered a standard cost plus fixed-fee contract, but the President of the company, Walter S. Carpenter, Jr., wanted no profit of any kind, and asked for the proposed contract to be amended to explicitly exclude the company from acquiring any patent rights. This was accepted, but for legal reasons a nominal fee of one dollar was agreed upon. After the war, DuPont asked to be released from the contract early, and had to return 33 cents.
A large crowd of sullen looking workmen at a counter where two women are writing. Some of the workmen are wearing identify photographs of themselves on their hats.
Hanford workers collect their paychecks at the Western Union office.
DuPont recommended that the site be located far from the existing uranium production facility at Oak Ridge. In December 1942, Groves dispatched Colonel Franklin Matthias and DuPont engineers to scout potential sites. Matthias reported that Hanford Site near Richland, Washington, was "ideal in virtually all respects". It was isolated and near the Columbia River, which could supply sufficient water to cool the reactors that would produce the plutonium. Groves visited the site in January and established the Hanford Engineer Works (HEW), codenamed "Site W".
Under Secretary Patterson gave his approval on 9 February, allocating $5 million for the acquisition of 40,000 acres (16,000 ha) of land in the area. The federal government relocated some 1,500 residents of White Bluffs and Hanford, and nearby settlements, as well as the Wanapum and other tribes using the area. A dispute arose with farmers over compensation for crops, which had already been planted before the land was acquired. Where schedules allowed, the Army allowed the crops to be harvested, but this was not always possible. The land acquisition process dragged on and was not completed before the end of the Manhattan Project in December 1946.
The dispute did not delay work. Although progress on the reactor design at Metallurgical Laboratory and DuPont was not sufficiently advanced to accurately predict the scope of the project, a start was made in April 1943 on facilities for an estimated 25,000 workers, half of whom were expected to live on-site. By July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As area engineer, Matthias exercised overall control of the site. At its peak, the construction camp was the third most populous town in Washington state. Hanford operated a fleet of over 900 buses, more than the city of Chicago. Like Los Alamos and Oak Ridge, Richland was a gated community with restricted access, but it looked more like a typical wartime American boomtown: the military profile was lower, and physical security elements like high fences, towers, and guard dogs were less evident.
Main article: Montreal Laboratory
Cominco had produced electrolytic hydrogen at Trail, British Columbia, since 1930. Urey suggested in 1941 that it could produce heavy water. To the existing $10 million plant consisting of 3,215 cells consuming 75 MW of hydroelectric power, secondary electrolysis cells were added to increase the deuterium concentration in the water from 2.3% to 99.8%. For this process, Hugh Taylor of Princeton developed a platinum-on-carbon catalyst for the first three stages while Urey developed a nickel-chromia one for the fourth stage tower. The final cost was $2.8 million. The Canadian Government did not officially learn of the project until August 1942. Trail's heavy water production started in January 1944 and continued until 1956. Heavy water from Trail was used for Chicago Pile 3, the first reactor using heavy water and natural uranium, which went critical on 15 May 1944.
The Chalk River, Ontario, site was established to rehouse the Allied effort at the Montreal Laboratory away from an urban area. A new community was built at Deep River, Ontario, to provide residences and facilities for the team members. The site was chosen for its proximity to the industrial manufacturing area of Ontario and Quebec, and proximity to a rail head adjacent to a large military base, Camp Petawawa. Located on the Ottawa River, it had access to abundant water. The first director of the new laboratory was Hans von Halban. He was replaced by John Cockcroft in May 1944, who in turn was succeeded by Bennett Lewis in September 1946. A pilot reactor known as ZEEP (zero-energy experimental pile) became the first Canadian reactor, and the first to be completed outside the United States, when it went critical in September 1945, ZEEP remained in use by researchers until 1970. A larger 10 MW NRX reactor, which was designed during the war, was completed and went critical in July 1947.
The Eldorado Mine at Port Radium was a source of uranium ore.
Heavy water sites
Main article: P-9 Project
Although DuPont's preferred designs for the nuclear reactors were helium cooled and used graphite as a moderator, DuPont still expressed an interest in using heavy water as a backup, in case the graphite reactor design proved infeasible for some reason. For this purpose, it was estimated that 3 short tons (2.7 t) of heavy water would be required per month. The P-9 Project was the government's code name for the heavy water production program. As the plant at Trail, which was then under construction, could produce 0.5 short tons (0.45 t) per month, additional capacity was required. Groves therefore authorized DuPont to establish heavy water facilities at the Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. Although known as Ordnance Works and paid for under Ordnance Department contracts, they were built and operated by the Army Corps of Engineers. The American plants used a process different from Trail's; heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.
The key raw material for the project was uranium, which was used as fuel for the reactors, as feed that was transformed into plutonium, and, in its enriched form, in the atomic bomb itself. There were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimsthal in Czechoslovakia, and in the Belgian Congo. All but Joachimstal were in allied hands. A November 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements. Nichols arranged with the State Department for export controls to be placed on uranium oxide and negotiated for the purchase of 1,200 short tons (1,100 t) of uranium ore from the Belgian Congo that was being stored in a warehouse on Staten Island and the remaining stocks of mined ore stored in the Congo. He negotiated with Eldorado Gold Mines for the purchase of ore from its refinery in Port Hope, Ontario, and its shipment in 100-ton lots. The Canadian government subsequently bought up the company's stock until it acquired a controlling interest.
While these purchases assured a sufficient supply to meet wartime needs, the American and British leaders concluded that it was in their countries' interest to gain control of as much of the world's uranium deposits as possible. The richest source of ore was the Shinkolobwe mine in the Belgian Congo, but it was flooded and closed. Nichols unsuccessfully attempted to negotiate its reopening and the sale of the entire future output to the United States with Edgar Sengier, the director of the company that owned the mine, Union Minière du Haut Katanga. The matter was then taken up by the Combined Policy Committee. As 30 percent of Union Minière's stock was controlled by British interests, the British took the lead in negotiations. Sir John Anderson and Ambassador John Winant hammered out a deal with Sengier and the Belgian government in May 1944 for the mine to be reopened and 1,720 short tons (1,560 t) of ore to be purchased at $1.45 a pound. To avoid dependence on the British and Canadians for ore, Groves also arranged for the purchase of US Vanadium Corporation's stockpile in Uravan, Colorado. Uranium mining in Colorado yielded about 800 short tons (730 t) of ore.
Mallinckrodt Incorporated in St. Louis, Missouri, took the raw ore and dissolved it in nitric acid to produce uranyl nitrate. Ether was then added in a liquid–liquid extraction process to separate the impurities from the uranyl nitrate. This was then heated to form uranium trioxide, which was reduced to highly pure uranium dioxide. By July 1942, Mallinckrodt was producing a ton of highly pure oxide a day, but turning this into uranium metal initially proved more difficult for contractors Westinghouse and Metal Hydrides. Production was too slow and quality was unacceptably low. A special branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding to investigate alternatives. This became known as the Ames Project, and its Ames process became available in 1943.
Uranium refining at Ames
A "bomb" (pressure vessel) containing uranium halide and sacrificial metal, probably magnesium, being lowered into a furnace
After the reaction, the interior of a bomb coated with remnant slag
A uranium metal "biscuit" from the reduction reaction
Natural uranium consists of 99.3% uranium-238 and 0.7% uranium-235, but only the latter is fissile. The chemically identical uranium-235 has to be physically separated from the more plentiful isotope. Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge.
The most obvious technology, the centrifuge, failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion technologies were all successful and contributed to the project. In February 1943, Groves came up with the idea of using the output of some plants as the input for others.
Contour map of the Oak Ridge area. There is a river to the south, while the township is in the north.
Oak Ridge hosted several uranium separation technologies. The Y-12 electromagnetic separation plant is in the upper right. The K-25 and K-27 gaseous diffusion plants are in the lower left, near the S-50 thermal diffusion plant. (The X-10 was for plutonium production.)
The centrifuge process was regarded as the only promising separation method in April 1942. Jesse Beams had developed such a process at the University of Virginia during the 1930s, but had encountered technical difficulties. The process required high rotational speeds, but at certain speeds harmonic vibrations developed that threatened to tear the machinery apart. It was therefore necessary to accelerate quickly through these speeds. In 1941 he began working with uranium hexafluoride, the only known gaseous compound of uranium, and was able to separate uranium-235. At Columbia, Urey had Karl Cohen investigate the process, and he produced a body of mathematical theory making it possible to design a centrifugal separation unit, which Westinghouse undertook to construct.
Scaling this up to a production plant presented a formidable technical challenge. Urey and Cohen estimated that producing a kilogram (2.2 lb) of uranium-235 per day would require up to 50,000 centrifuges with 1-meter (3 ft 3 in) rotors, or 10,000 centrifuges with 4-meter (13 ft) rotors, assuming that 4-meter rotors could be built. The prospect of keeping so many rotors operating continuously at high speed appeared daunting, and when Beams ran his experimental apparatus, he obtained only 60% of the predicted yield, indicating that more centrifuges would be required. Beams, Urey and Cohen then began work on a series of improvements which promised to increase the efficiency of the process. However, frequent failures of motors, shafts and bearings at high speeds delayed work on the pilot plant. In November 1942 the centrifuge process was abandoned by the Military Policy Committee following a recommendation by Conant, Nichols and August C. Klein of Stone & Webster.
Although the centrifuge method was abandoned by the Manhattan Project, research into it advanced significantly after the war with the introduction of the Zippe-type centrifuge, which was developed in the Soviet Union by Soviet and captured German engineers. It eventually became the preferred method of Uranium isotope separation, being far more economical than the other separation methods used during WWII.
Main article: Y-12 Project
Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and the cyclotron magnet. The name was derived from the words California, university and cyclotron. In the electromagnetic process, a magnetic field deflected charged particles according to mass. The process was neither scientifically elegant nor industrially efficient. Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity.
A large oval-shaped structure
Alpha I racetrack at Y-12
Marshall and Nichols discovered that the electromagnetic isotope separation process would require 5,000 short tons (4,500 tonnes) of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 ratio. On 3 August 1942, Nichols met with Under Secretary of the Treasury Daniel W. Bell and asked for the transfer of 6,000 tons of silver bullion from the West Point Bullion Depository. "Young man," Bell told him, "you may think of silver in tons but the Treasury will always think of silver in troy ounces!" Eventually, 14,700 short tons (13,300 tonnes; 430,000,000 troy ounces) were used.
The 1,000-troy-ounce (31 kg) silver bars were cast into cylindrical billets and taken to Phelps Dodge in Bayway, New Jersey, where they were extruded into strips 0.625 inches (15.9 mm) thick, 3 inches (76 mm) wide and 40 feet (12 m) long. These were wound onto magnetic coils by Allis-Chalmers in Milwaukee, Wisconsin. After the war, all the machinery was dismantled and cleaned and the floorboards beneath the machinery were ripped up and burned to recover minute amounts of silver. In the end, only 1/3,600,000th was lost. The last silver was returned in May 1970.
Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first-stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943.
When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings. The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.
A long corridor with many consoles with dials and switches, attended by women seated on high stools
Calutron Girls were young women who monitored calutron control panels at Y-12. Gladys Owens, seated in the foreground, was unaware of what she had been involved with until seeing this photo on a public tour of the facility 50 years later. Photo by Ed Westcott.
Tennessee Eastman was contracted to manage Y-12 on the usual cost plus fixed-fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack. The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly" girl operators were outperforming his PhDs. They agreed to a production race and Lawrence lost, a morale boost for the Tennessee Eastman workers and supervisors. The girls were "trained like soldiers not to reason why", while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials."
Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By August K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.
Main article: K-25
The most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen, and John R. Dunning.
Oblique aerial view of an enormous U-shaped building
Oak Ridge K-25 plant
In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant. On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A cost plus fixed-fee contract was negotiated, eventually totaling $2.5 million. A separate corporate entity called Kellex was created for the project, headed by Percival C. Keith, one of Kellogg's vice presidents. The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride would have to be used, as no substitute could be found, and the motors and pumps would have to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which would have to be strong, porous and resistant to corrosion by uranium hexafluoride. The best choice for this seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the Norris-Adler prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production.
Kellex's design for K-25 called for a four-story 0.5-mile (0.80 km) long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections. Within these were cells of six stages. The cells could be operated independently, or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction by marking out the 500-acre (2.0 km2) site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages of the plant, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million.
The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.
Main article: S-50 Project
The thermal diffusion process was based on Sydney Chapman and David Enskog's theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. Since hot gases tend to rise and cool ones tend to fall, this can be used as a means of isotope separation. This process was first demonstrated by Klaus Clusius and Gerhard Dickel in Germany in 1938. It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part.
A factory with three smoking chimneys on a river bend, viewed from above
The S-50 plant is the dark building to the upper left behind the Oak Ridge powerhouse (with smoke stacks).
The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain William S. Parsons, the naval officer in charge of ordnance development at Los Alamos, brought Oppenheimer news of encouraging progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output of a thermal diffusion plant could be fed into Y-12. Groves set up a committee consisting of Warren K. Lewis, Eger Murphree and Richard Tolman to investigate the idea, and they estimated that a thermal diffusion plant costing $3.5 million could enrich 50 kilograms (110 lb) of uranium per week to nearly 0.9% uranium-235. Groves approved its construction on 24 June 1944.
Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Groves's advisers, Karl Cohen and W. I. Thompson from Standard Oil, estimated that it would take six months to build. Groves gave Ferguson just four. Plans called for the installation of 2,142 48-foot-tall (15 m) diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of 100 pounds per square inch (690 kPa) and temperature of 545 °F (285 °C), flowed downward through the innermost 1.25-inch (32 mm) nickel pipe, while water at 155 °F (68 °C) flowed upward through the outermost iron pipe. The uranium hexafluoride flowed in the middle copper pipe, and isotope separation of the uranium occurred between the nickel and copper pipes.
Work commenced on 9 July 1944, and S-50 began partial operation in September. Ferguson operated the plant through a subsidiary known as Fercleve. The plant produced just 10.5 pounds (4.8 kg) of 0.852% uranium-235 in October. Leaks limited production and forced shutdowns over the next few months, but in June 1945 it produced 12,730 pounds (5,770 kg). By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching from 0.71% to 0.89%. This material was fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. This was, in turn, fed into Y-12, which boosted it to about 89%, sufficient for nuclear weapons.
Aggregate U-235 production
About 50 kilograms (110 lb) of uranium enriched to 89% uranium-235 was delivered to Los Alamos by July 1945. The entire 50 kg, along with some 50%-enriched, averaging out to about 85% enriched, were used in Little Boy.
The second line of development pursued by the Manhattan Project used the fissile element plutonium. Although small amounts of plutonium exist in nature, the best way to obtain large quantities of the element is in a nuclear reactor, in which natural uranium is bombarded by neutrons. The uranium-238 is transmuted into uranium-239, which rapidly decays, first into neptunium-239 and then into plutonium-239. Only a small amount of the uranium-238 will be transformed, so the plutonium must be chemically separated from the remaining uranium, from any initial impurities, and from fission products.
X-10 Graphite Reactor
Main article: X-10 Graphite Reactor
Two workmen on a movable platform similar to that used by window washers, stick a rod into one of many small holes in the wall in front of them.
Workers load uranium slugs into the X-10 Graphite Reactor.
In March 1943, DuPont began construction of a plutonium plant on a 112-acre (0.5 km2) site at Oak Ridge. Intended as a pilot plant for the larger production facilities at Hanford, it included the air-cooled X-10 Graphite Reactor, a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot. The X-10 Graphite Reactor consisted of a huge block of graphite, 24 feet (7.3 m) long on each side, weighing around 1,500 short tons (1,400 t), surrounded by 7 feet (2.1 m) of high-density concrete as a radiation shield.
The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These somehow had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a hot dipping process without success. Meanwhile, Alcoa tried canning. A new process for flux-less welding was developed, and 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of General Electric, which was incorporated into the production process in October 1943.
Watched by Fermi and Compton, the X-10 Graphite Reactor went critical on 4 November 1943 with about 30 short tons (27 t) of uranium. A week later the load was increased to 36 short tons (33 t), raising its power generation to 500 kW, and by the end of the month the first 500 mg of plutonium was created. Modifications over time raised the power to 4,000 kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research activities.
Main article: Hanford Site
Although an air-cooled design was chosen for the reactor at Oak Ridge to facilitate rapid construction, it was recognized that this would be impractical for the much larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor would be simpler, cheaper and quicker to build. The design did not become available until 4 October 1943; in the meantime, Matthias concentrated on improving the Hanford Site by erecting accommodations, improving the roads, building a railway switch line, and upgrading the electricity, water and telephone lines.
An aerial view of the Hanford B-Reactor site from June 1944. At center is the reactor building. Small trucks dot the landscape and give a sense of scale. Two large water towers loom above the plant.
Aerial view of Hanford B-Reactor site, June 1944
As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944. They were pickled to remove dirt and impurities, dipped in molten bronze, tin, and aluminum-silicon alloy, canned using hydraulic presses, and then capped using arc welding under an argon atmosphere. Finally, they were subjected to a series of tests to detect holes or faulty welds. Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful of canned slugs per day. But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs would be available to start Reactor B on schedule in August 1944.
Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943. The reactor complexes were given letter designations A through F, with B, D and F sites chosen to be developed first, as this maximised the distance between the reactors. They would be the only ones constructed during the Manhattan Project. Some 390 short tons (350 t) of steel, 17,400 cubic yards (13,300 m3) of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the 120-foot (37 m) high building.
Construction of the reactor itself commenced in February 1944. Watched by Compton, Matthias, DuPont's Crawford Greenewalt, Leona Woods and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944. Over the next few days, 838 tubes were loaded and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production. At first all appeared well but around 03:00 the power level started to drop and by 06:30 the reactor had shut down completely. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor started up again, only to shut down once more.
Fermi contacted Chien-Shiung Wu, who identified the cause of the problem as neutron poisoning from xenon-135, which has a half-life of 9.2 hours. Fermi, Woods, Donald J. Hughes and John Archibald Wheeler then calculated the nuclear cross section of xenon-135, which turned out to be 30,000 times that of uranium. DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners. The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium. Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945.
A contour map showing the fork of the Columbia and Yakima rivers and the boundary of the land, with seven small red squares marked on it
Map of the Hanford Site. Railroads flank the plants to the north and south. Reactors are the three northernmost red squares, along the Columbia River. The separation plants are the lower two red squares from the grouping south of the reactors. The bottom red square is the 300 area.
Meanwhile, the chemists considered the problem of how plutonium could be separated from uranium when its chemical properties were not known. Working with the minute quantities of plutonium available at the Metallurgical Laboratory in 1942, a team under Charles M. Cooper developed a lanthanum fluoride process for separating uranium and plutonium, which was chosen for the pilot separation plant. A second separation process, the bismuth phosphate process, was subsequently developed by Seaborg and Stanly G. Thomson. This process worked by toggling plutonium between its +4 and +6 oxidation states in solutions of bismuth phosphate. In the former state, the plutonium was precipitated; in the latter, it stayed in solution and the other products were precipitated.
Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and it was selected for the Hanford separation plants. Once X-10 began producing plutonium, the pilot separation plant was put to the test. The first batch was processed at 40% efficiency but over the next few months this was raised to 90%.
At Hanford, top priority was initially given to the installations in the 300 area. This contained buildings for testing materials, preparing uranium, and assembling and calibrating instrumentation. One of the buildings housed the canning equipment for the uranium slugs, while another contained a small test reactor. Notwithstanding the high priority allocated to it, work on the 300 area fell behind schedule due to the unique and complex nature of the 300 area facilities, and wartime shortages of labor and materials.
Early plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. This was subsequently reduced to two, the T and U plants, in 200-West and one, the B plant, at 200-East. Each separation plant consisted of four buildings: a process cell building or "canyon" (known as 221), a concentration building (224), a purification building (231) and a magazine store (213). The canyons were each 800 feet (240 m) long and 65 feet (20 m) wide. Each consisted of forty 17.7-by-13-by-20-foot (5.4 by 4.0 by 6.1 m) cells.
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