Build a Fusion Reactor

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Introduction: Build a Fusion Reactor

Yes, you can build your very own nuclear fusion reactor in your house! But first, a few warnings:

-This project includes lethal voltage levels. Make sure you know your high voltage safety or have a qualified electrical advisor.
-Potentially hazardous levels of x-rays will be produced. Lead shielding of viewports is a must!
-Deuterium, an explosive gas, will be used. Make sure to check for fuel leaks.
-All the other inherent dangers of a home engineering project of this degree (a wide gamut of potential injuries, damage to the checking account, and the loss of general sanity)



Here are the minimum required materials:

-A vacuum chamber, preferably in a spherical shape
-A roughing vacuum pump capable of reaching at least 75 microns vacuum
-A secondary high vacuum pump, either a turbo pump or oil diffusion pump
-A high voltage supply, preferably capable of at least 40kv 10ma - Must be negative polarity
-A high voltage divider probe for use with a digital multimeter
-A thermocouple or baratron (of appropriate scale) vacuum gauge
-A neutron radiation detector, either a proportional He-3 or BF3 tube with counting instrumentation, or a bubble dosimeter
-A Geiger counter, preferably a scintillator type, for x-ray detection and safety
-Deuterium gas (can be purchased as a gas or extracted from D2O through electrolysis - it is much easier and more effective to use compressed gas)
-A large ballast resistor in the range of 50-100k and at least a foot long
-A camera and TV display for viewing the inside of the reactor
-Lead to shield the camera viewport
-General engineering tools, a machine shop if at all possible (although 90% of mine was built with nothing but a dremel and cordless drill, the only thing you really can't build without a shop is scratch building the vacuum chamber)

Step 1: Assemble the Vacuum Chamber

A quality high vacuum chamber is required for the fusor to operate. Sometimes an appropriate chamber can be found on eBay, but generally it is best to make one. Parts can be scrounged for several hundred dollars, or purchased new for $500+.

Get two stainless steel hemispheres, purchase two corresponding conflat-flanges (8" flanges in my case), bore out holes for accessory flanges, and then TIG weld it all together. Flanges are typically either of the KF or the conflat style. Conflat can be seen in the image below as the flanges with bolts, and KF (kwik-flange) are seen as those with only clamps holding an o-ring on the mating surface. Only weld on the inside, never on the outside (since virtual leaks can be formed if both inside and outside are welded). If you've never TIG welded before, it would be wise to have someone with experience do it as the welds must be flawless with no pin-sized holes or porous areas to hold a vacuum.

After machining, thoroughly clean the chamber and avoid getting fingerprints in it since these will outgas, which means at vacuum pressure molecules in the oil of finger prints or machining oil will become vapor and make it hard to maintain plasma stability or reach a good ultimate vacuum level.

Step 2: Prepare the High Vacuum Pump

Install the oil diffusion pump (or turbo pump if you have a bit of luck scrounging or a higher budget). Fill the pump with quality diffusion pump oil to whatever fill level the pump documentation suggests, attach the inlet to a valve which then connects to the chamber (see diagram), and attach the outlet to a mechanical backing pump capable of reaching at least around 75 microns (any higher and the diffusion pump will not operate properly or the oil will oxidize quickly).

Make sure the pump is sufficiently cooled, many oil diffusion pumps require water cooling, smaller ones such as the one pictured can get by with a decent air flow.

Once this is assembled, turn on the mechanical pump and wait for the vacuum to reach at least 75 microns. Next you can test the high vacuum pump by turning on the boiler on the diffusion pump. After it warms up (could take a while), the vacuum should rapidly drop below the single micron range.

Step 3: Build Inner Grid

The inner grid (where the high voltage is applied) must now be built and attached to a high voltage feedthrough.

It is best to use a metal such as tungsten for the grid wires since it has a very high melting point, and the grid will get extremely hot during high power runs.

This can be built however you wish, as long as it resembles a spherical shape of roughly 1-1.5 inches in diameter (for a 6-8" chamber), it should work fine.

The grid should be internally attached to an electrical feedthrough such as the one pictured in the second image. This feedthrough needs to be rated for the cathode voltage that will be used, typically 40kv is a good target voltage.

Step 4: Assemble the Deuterium System

Deuterium gas is used as the fuel for this fusion reactor. You will need to purchase a tank of this gas (unless you wish to do electrolysis on heavy water, this process will not be documented here but nothing more than a small Hoffman Apparatus is required - higher purity gas can be gotten from a compressed tank).

Attach a high pressure regulator directly to the tank, add an extremely fine-metering needle valve after this (or a laser drilled orifice in the range of 5 microns), then attach this to the chamber. A ball valve can also be installed between the regulator and the needle valve since needle valves are not shutoff valves.

See the attached diagram now updated with the deuterium handling system.

Step 5: High Voltage

If you can purchase a power supply (occasionally but not commonly found surplus) appropriate for fusion use, the high voltage becomes very simple. Simply take the output of the 40kv negative supply and attach it to the chamber with a physically large high voltage 50-100k ohm ballast resistor in series (large enough that its length will not flash-over if 40kv is applied to it in a plasma run-away or arc discharge).

The difficulty is that it is often difficult if not impossible to find an appropriate fully assembled DC supply of this voltage level that is affordable to the amateur scientist.

Pictured is my high frequency ferrite transformer pair, with a 4-stage multiplier seen behind it.

If a fully assembled power supply (typically manufactured by either Glassman or Spellman), there are a few options:
-Find an x-ray transformer, and if necessary either reverse the rectifiers for negative polarity or add rectifiers if it has none (an x-ray transformer core won't have rectifiers, it probably will if it is in its oil tank)
-Build a switching high frequency ferrite power supply. This is what I did, however it requires a bit of EE experience since several aspects must be resonant and if it is ever taken out of tune, the transistors will burn out. Probably not the best option for people with little electrical background.

Step 6: Setup Neutron Detection

The proof of fusion (and a quantitative analysis of how much fusion) is obtained through detecting neutron radiation, the byproduct of a D-D fusion reaction. There are three options which will be described. They are in order of descending ease of setup.


-A Neutron Bubble Dosimeter
A bubble dosimeter is a small unit with a gel in it that forms bubbles when ionized by neutron radiation. This is the easiest form of neutron detection available since all you have to do is unscrew the top and set it next to the fusor. Some of the drawbacks are that it is an integrative detector which means all you get is a total neutron emission number over the time that it was used, rather than an instantaneous neutron rate. Additionally, they are somewhat hard to get since the only company to make them is Bubbletech in Canada, which has a minimum order of 3 with steep shipping and handling (expect to spend $700+ if ordering directly from them not in a group buy). Additionally, they tend to be fairly worn out after a year of shelf life (although I've kept mine in a refrigerated storage container at 50*F and it seems to be like new after I think more than a year). The advantage is that calibration data is provided with purchase and of course it is easy.

-Silver Activation
When silver is placed near the reactor (with a moderator [paraffin wax, water, HDPE, etc] between it and the neutron source, since only thermal neutrons will activate the material) it becomes slightly radioactive with decent neutron fluxes. It has a short half life of only a few minutes, but if you quickly put a geiger counter next to the silver, counts can be detected. In my best runs, I have gotten a piece of silver to about 250CPM over background on a CDV-700 geiger-counter. The disadvantages of this are that it requires a decent neutron flux (at least about 100,000 neutrons/s) which is above the average "beginner's first run" neutron rate. Also, it is somewhat difficult to calibrate, and the counts can't be taken until after the fusor has been shut off.

-A Proportional Tube
Tubes can be purchased which are filled with either BF3 or Helium-3 (some very old tubes are Boron-10 lined inert gas tubes). These tubes, similar to a geiger counter, can be used with a counting device to detect electrical pulses when neutrons pass through the tube. Either an all-in-one counter can be used, often made by a company called Ludlum, or a modular counting system can be made using NIM modules. The tube is surrounded by about 2 inches of moderating material such as wax or water. This is by far the most accurate and useful form of neutron detection, however the cost of a new tube is prohibitive to most people, and they are extremely rare on the surplus market. Also, counting equipment can become quite costly.

NIM Configuration: If you chose to make a NIM setup as I have, the typical layout is a charge sensitive pre-amplifier at the head of the proportional tube, which is plugged into both a high voltage power supply generating positive polarity voltage appropriate for the tube (in the range of 800V-2kV generally). The amplifier also hooks into a shaping amplifier, which is followed by a Single Channel Analyzer (for setting the detection discrimination level), followed by a pulse counter and/or rate meter.


Shown in the first picture is my NIM setup, the second picture is the pre-amplifier attached to a moderated helium-3 tube, the third picture is a bubble detector after being exposed to neutrons.

Step 7: Fire It Up (and Cross Your Fingers)

Time to turn it on (don't forget to cover any viewports/cameras with lead! Also x-rays can pour out of ceramic feedthroughs so point them away from people. It is a good idea to be monitoring for x-rays where any people are present). The basic procedure is:

-Turn on the roughing pump and wait for sufficient backing pressure, turn on the diffusion or turbo pump and wait for it to fully warm up or achieve running speed
-Throttle the chamber back (with the valve between the diffusion/turbo pump and the chamber)
-Ever so slightly open the needle valve to the deuterium tank
-Turn up the high voltage until either plasma establishes on the camera, or you've reached 40kv and nothing has happened (don't forget, you only get one chance in your life to screw up with voltages of this degree)
-If nothing has happened, keep admitting more gas and the pressure should keep going up. Plasma should form around 40kv at about 10-15 microns of deuterium.

If all goes well, you should see on your camera the image below, and you should be detecting neutrons at this point.

Operation is quite a balancing act, since the voltage is controlled by both the power supply, but also by Paschen's Curve and Ohm's Law relating to the pressure in the chamber. Great patience is required to "Get the hang of it", but after doing so it becomes quite simple to run. Operation can be aided by an ion-gun which will not be discussed in this article.

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779 Discussions

0
noahwpw
noahwpw

Question 10 hours ago on Introduction

Can someone please link some of the item including in this project

0
ArduinoPi
ArduinoPi

Reply 11 days ago

IDK, but amazon sells tritium.

0
robinson.wyatt
robinson.wyatt

Reply 11 months ago

Buy heavy water online and then use electrolysis to separate the oxygen from the deuterium.

0
ayranman123
ayranman123

Reply 1 year ago

Find*

0
DylanC91
DylanC91

2 years ago

I don't no much about any of this, but how much electricity will this produce? Can it power a house for a year (or something like that)?

Forgive me if this is just a crazy or irrelevant question - I'm really inexperienced with any of this, and was really just wondering.

0
ArduinoPi
ArduinoPi

Reply 11 days ago

I think it's just a reactor. Most experimental fusion plants require more energy than they produce.

0
cadence236
cadence236

Reply 8 months ago

the main point of it is to DO fusion and produce nuetrons. The fusion energy produced in a functioning fusor is far too sparse in nature. The fusion energy is lost in the noise and waste of electrical energy needed to produce it.

0
norseking2
norseking2

Reply 1 year ago

It doesn’t produce power

0
24vynoriusc
24vynoriusc

Reply 1 year ago

A reactor can power a house for mabye 10 years because some citys us them for power.

1
notanomnom
notanomnom

Reply 2 years ago

Also sorry for resurrecting a post, but it's gotta be said that this project will not produce any excess energy. That is what scientists have been trying to achieve for decades and are still trying. This reactor is only really useful for experimentation, maybe for people with the dream of doing what all the other scientists cant.

0
skyler.edgar1014
skyler.edgar1014

Reply 2 years ago

(also don't understand much of this)

The general ideal of it is to create a high level amount of energy but that ideal is typically (always) impossible because of the variables of attempting the reformatting of energy, pretty much it uses more energy than it can create.

0
DylanC91
DylanC91

Reply 2 years ago

Thanks for replying. Would you say, then, this project probably wouldn't be a good idea to make in effort to power your house like one would use solar panels, etc. as a sustainable energy source? Crazy idea, but is really just for recreational thought.

0
christianm298
christianm298

Reply 2 years ago

Don't mean to bring resurrect this old post but does this reactor produce any neutron radiation? I'm trying to build a betavoltaic power supply but am in short stock of nickel-63 (For obvious reasons) and am attempting to find ways to produce it myself.

0
SHOE0007
SHOE0007

4 years ago

Is this even legal since you are maxing radiation which requires a permit.

0
RikHoutman
RikHoutman

Reply 4 years ago

depens on the country you live in. In the US you need permession but that's just that no 12 year old's are going to try this

0
offgridsid
offgridsid

Reply 3 years ago

A late reply, I know and I'm trying to be Nice ... but Sorry, you are incorrect ... WE are Americans and we don't ever ask permission (especially from the Government) for ANYTHING (including building Nuclear Reactors) that we might wish to do. Also, one of the better designs WAS designed and built by a 12 year old ... American.

0
william.tb.lawyer
william.tb.lawyer

Reply 3 years ago

lol, I know. I am not even old enough to drive and am looking into building a fission generator for my science project since I really want to win and last years hydrogen battery only got me third place. Age is not even relevant.

0
bm1001722
bm1001722

Reply 3 years ago

im tying to buy this

https://www.google.com/maps/place/Shoreham+Nuclear...

im 12

my friend is 12

we are teaching our self's nuclear physics and hoping we can get authorization to get the plant running again.

also i have 1 year to beat the record for youngest.

1
william.tb.lawyer
william.tb.lawyer

Reply 3 years ago

Well, that's quite an ambitious goal for a 12 year old, but certainly not unattainable. Me and my friends didn't really start getting into nuclear physics until we were around 13, and its not something they really teach you in school at that age, so you are going to have to teach yourself practicaly all of it. The biggest problem with the Shoreham nuclear power plant was public opposition since most people don't really have any idea how a nuclear power plant works, and their brains are just kind of wired to "Nuclear, big explosion, radiation bad." If you plan to reopen that, you are going to have to find a way to get New York State officials on board with your plan, which is not going to be easy. If I remember right the plant was also fully decommissioned, and it is a older model as well, so it is not going to be nearly as efficient and safe as the designs we have now. You will also need a license to do any work on that reactor as well, start here: https://www.nrc.gov/about-nrc/regulatory/licensing.html, but I warn you, nuclear licences are never cheap, but as a small entity rather than a large corporation it will be significantly easier to get such such a licence.

I would also like to add that the plant in question is a fission power plant, and as far as I know, no individual has ever build one by themselves. Jamie Edwards currently holds the title for being the youngest person to construct a fusion reactor at age 13, but you got plenty of time if you want to build a fission reactor, since you would be the first to ever build one as an individual.

(Taylor Wilson has designed a small scale Fission reactor, but as far I know his design was never built. Contact me if you need any help!)