Endoscopes Megaphones Uranium
Today on "how it's made"... Endoscopes... Megaphones... And uranium. An endoscope is a tube with optical glass fibers and lenses inside attached to a video camera. Doctors feed the endoscope through the patient's mouth or other opening or insert it through a tiny incision then watch what the camera captures on a video monitor. An endoscope lets the surgeon see inside the patient during an examination or surgical procedure. Its light-transmitting optical fibers work like a flashlight inside the body. The optical fiber manufacturer suspends glass rods from the top of a tall oven, which heats them to a melting temperature of 1,652 degrees fahrenheit. Each rod drips downward in the form of a thin strand. A guide wheel turns this glass fiber in a horizontal direction. The fiber then winds on to a drum, whose rotation speed stretches it to a specific hair-thin diameter. A worker combines several single fiber spools on to a large winding wheel to make a bundle containing thousands of fibers. To make the cable that connects a light source in the operating room to the endoscope, a worker inserts an optical fiber bundle into a silicon cable sheathing. This one has nearly 9,000 fibers. She screws a stainless steel fastener, called a ferrule on to each threaded end of the sheathing. After saturating the ferrules and optical fibers inside with glue and curing the adhesive with heat, the worker trims off excess fibers and hands off the cable to the next station, where a work polishes both ends. Polishing finalizes the dimensions and enables light to shine through. This quality control test, one of several, ensures the fibers can withstand a prescribed amount of pressure without cracking. The optical fiber manufacturer also supplies fiber spools to the endoscope manufacturer for the light transmission system inside the endoscope. Workers cut the bundle of optical fibers to the length required for the endoscope model they're making. Endoscopes vary in length and diameter, depending on the part of the body they're designed for. After verifying that the diameter of the bundle is correct, they tie the optical fibers with string to hold them together during insertion. Then workers insert the fiber bundle between the inner and outer stainless steel sheathes that make up the main body of the endoscope, pushing the fibers down the length of the inner sheath. They attach a stainless steel adaptor. This will connect the light cable from the operating room light source to the endoscope, transferring light to the optical fibers inside the endoscope. A worker inspects those fibers under magnification for black spots. Black spots indicate broken fibers, which would interrupt the transmission of light. An endoscope transmits an image much like a telescope does. Optical lenses send reflected light, which produces the image, from inside the patient all the way up to your eye peering through the top. The lenses in the endoscope are glass rods. After cleaning them with chemical solution, workers line them up in a fixture with brass spacers of various lengths in between. Depending on the length of the endoscope, there are five to seven lenses. The spacers create specific distances between them. Once workers have assembled the image transmission system, they gently slide it off the fixture into the inner sheath of the endoscope. Then, they screw on an ocular cap to hold it all in place. A worker cleans the cap's glass top, then attaches an eyepiece. This gives the surgeon the option of either looking directly into the endoscope or looking at an operating room video monitor which receives the image via a small camera attached to the eyepiece. This demonstration shows how it all comes together in the operating room. After securing the endoscope in a holding fixture, the surgeon attaches the light cable coming from the nearby light source. The light travels down and out the endoscope, illuminating the area that surgeon's working on. The lenses reflect the image to the top of the endoscope, where a camera transmits it to a video monitor that's mounted in front of the surgeon. In the beginning, megaphones were simply cone-shaped devices that focused sound forward so it went further and could be heard more clearly. In the 20th century microphones, an amplifier and a speaker were added to the cone, and that really ramped up the volume. With a megaphone, there's no need to shout. Just speak, and you will be heard. This waterproof version is designed for coaching, law enforcement, and military uses. Production starts with a panel of four digital circuit boards that have little gold pads on them. An assembler places a stencil over the panel and aligns the stencil holes with the gold pads. He then squeegee's solder paste down the stencil, and it flows on to the exposed gold pads. This is before and after the solder past application. Robotic arms install electrical components on the solder-coated pads, creating circuitry. Various reels unwind to deliver these little parts. The robotic arms suction them off liners and transfer them to precise locations on the boards. The parts will run the megaphone's sirens, horns, and microphones. A technician clamps one of the completed circuit boards in a tester. Spring-loaded pins underneath make electrical contacts with the components and probe their performance. The system runs a full test of the circuitry. At the next station, an assembler attaches a part known as the front can to the end of a flared speaker cone. He then turns his attention to the speaker. The assembler inserts screws in the base. He threads wires from the speaker through a hole in the cone and through the front can. The assembler then places the speaker in the cone, and he screws it in place. He attaches a connector to the protruding speaker wires. The worker places a mesh metal screen over a hole in the rear can. The assembler taps a nut driver with a hammer to force the mesh into the hole, and this shapes the mesh into a microphone cover. He removes the newly-formed mic cover and fits it to the mic, manually crimping it around the sides for a snug fit. He now tucks the microphone into a tube that has a sliding inner sleeve. The assembler inserts the tube into the microphone hole in the rear can. He slides the inside tube down to push the microphone in the hole. He secures the knob for turning the megaphone on and for adjusting the volume. The assembler installs a mini-circuit board that's linked to the siren and horn button. These small spring pins will mate to a battery to power the megaphone's circuitry. He tucks the pins into molded protrusions inside the rear can and waterproofs them with rubber o-rings. This megaphone subassembly is now ready for the main circuit board. The assembler threads wires for this switch trigger, microphone, siren, and horn through holes in the board. He then screws the board to the rear housing. He fits a silicon o-ring around the rim of the rear can to seal it. The assembler then joins the rear can with all the working parts to the front can and cone assembly. He connects the speaker wires to the circuit board. This megaphone is now ready for a sound test. The technician connects it to a temporary battery and powers it up. Check, one, two. One, two. Check, testing, testing. One, two, test. More sensitive testing is needed. He encloses the megaphone in an insulated chamber to shut out background noises. A computer runs the megaphone at different frequencies and analyzes its performance. Once the megaphone passes these tests, they install handles. And now it's ready for anything you have to say. Uranium is a metallic element that was discovered by a german chemist in 1789. The significance of this discovery wasn't understood for a century and a half. In 1938, scientists figured out that uranium atoms could be split to produce energy. The size of a fireplace log, this nuclear fuel bundle generates a lot more heat. It's packed with enough uranium to power 100 homes for a year. To obtain the uranium, the tunnel 1,640 feet underground at this site in northern saskatchewan. This mine is the largest source of high-grade uranium in the world. The uranium ore lies beneath a bed of water-saturated sandstone. To reach it, they use drill bits studded with tungsten carbide buttons. Like knuckles on a fist, the button bits punch into the rock face. These first holes are for pipes that will pull heat out of the ground and freeze it around the ore. The miner operates the equipment by remote control. It transfers a new piece of pipe to the end of the drill roughly every five feet to penetrate 426 feet into the sandstone bed. It takes up to eight days to install just one length of pipe, and there are 200 of them. Workers configure the pipes so they surround the ore deposit. These freeze pipes will stabilize the ground, and they'll also turn high-pressure ground water to ice, so it won't interfere with the actual mining. A freeze plant above ground chills calcium chloride brine to minus-22 degrees fahrenheit and sends it through the freeze pipes. The brine absorbs heat as it freezes the ground and loops back to be chilled again. Above the uranium deposits, workers now gear up to mine the ore. They'll use this bit to chew into the ore body in order to make an initial small-diameter hole known as a pilot hole. The pilot hole maps out the drill route to ore, and it creates an entry point for larger mining equipment. From a raised position, the bit bores vertically into the rock to drill the pilot hole and reach a specific level below the ore body. They're now ready for the reamer bit. The reamer has numerous button-encrusted wheel tentacles. As this animation shows, the drill pulls the reamer up the pilot hole, widening it. And the broken ore falls into what's known as an extraction chamber. Here, a tram operated by remote control scoops up the rock. This remote control system keeps miners a safe distance away from falling rock hazards. It also minimizes their exposure to the radioactive uranium in the ore. As another precaution, workers continuously ventilate the mine, introducing fresh air every 20 minutes. Steered by the operator's joystick, the tram delivers the ore to a scanner. By measuring the amount of radioactivity in the ore, the scanner determines the uranium content is about 15%. In much of the ore, the uranium content is even greater-- on average, around 18%, and that's considered to be very high-grade. The train now empties the ore into a chute. Cameras follow the rocks' journey to the next station. Then from a control room, an operator manipulates a hydraulic hammer to smash the ore to bits. The broken ore then migrates to a mill that grinds it into a fine sand. They add water, and it becomes slurry, which they then pump to the surface. Trucks then transport the uranium ore slurry to a mill nearly 50 miles away. They pull into a special off-loading facility. The support for a vacuum system aligns with the tote that encases the slurry tank. Once in position, a vacuum pipe drops into the tank and suctions up the slurry. Cameras provide a live feed of the unloading progress to a control room almost 23 feet away. After a wash and a radiation check, the truck leaves. Stay tuned for the transformation of uranium into nuclear fuel. Just one fuel bundle of uranium contains the same amount of energy as just over 71,000 gallons of oil. But uranium can't simply be chipped away from the rock it resides in. It must be chemically separated and processed to make it into usable fuel for a nuclear reactor. Acid dissolves the uranium, but not the rest of the rock. It settles to the bottom of these tanks. The uranium-acid solution flows forward, leaving the unwanted minerals behind. Using a series of chemical reactions, they further purify the uranium. They then roast it at 1,562 degrees fahrenheit. This concentrates it into a jet-black powder. The uranium powder flows into 55-gallon steel drums. A worker taps the lip of the drum to remove residual powder. He then puts the lid on and activates a press that secures it tightly to the drum. As an extra precaution, he seals it with a steel ring. He labels it to indicate the drum's contents, weight, and radioactivity. Workers stack the drums in a warehouse to await shipment to the next processing plant. There, the uranium goes from black to yellow as they convert it to uranium trioxide, an interim chemical form in the processing chain. They ship the uranium trioxide in specially designed inverted cones. Upon arrival at the next facility, a valve opens at the bottom and the powder flows into conveyor tubes that take it into the plant. Inside, workers dissolve the uranium trioxide powder in acid. A worker takes a sample to test the density and the chemistry and confirms that both are acceptable. They then add a chemical to turn the dissolved uranium back into a solid. After more processing, the uranium trioxide becomes uranium dioxide, the chemical form required for nuclear fuel. Spinning the uranium dioxide mixes the different sized particles to make it a more homogenous blend. The chemical processing has also caused the uranium to change color again. It is now a fine black powder. Using several tons of pressure, tools shape the uranium dioxide into pellets. A revolving wheel with protrusions guides the pellets into a channel conveyor. The conveyor takes the pellets into a furnace. Over 24 hours, the heat removes pores in the pellets. The pellets shrink, increasing the density of the uranium. The particles fuse together and harden into a ceramic. Here's a pellet before and after baking. A robot arm now loads the pellets on to a tray and levels them. A conveyor moves the tray forward. Ahead, another robot places zirconium fuel tubes on a rack. Zirconium is a metal that's highly resistant to both heat and corrosion, but neutrons will pass freely through it during the fission reaction. The rack of tubes meet up with a tray of incoming pellets. A robotic loader pushes the stack of 30 pellets into the tube. Another robot delivers the rods one at a time to an automated welder that caps the ends. The next robot retrieves the completed uranium fuel rods and transfers it to an assembly fixture. It arranges a total of 37 rods in an upright position within the fixture. After the rods have been welded and the bundle capped at both ends, a robot transfers it to a scale. This weigh-in confirms that there is the correct amount of uranium in the bundle. Prior to burn up in a reactor, the amount of radioactivity emitted by nuclear fuel bundles is very low, and they're safe to handle as workers prepare them for shipping. They're now on their way to the power plant, where they'll be sure to generate a reaction.