This map lists "nuclear power plants" and therefore is missing research reactors.
Any research reactor contains a critical mass of fuel, and therefore is fully capable of meltdown.
Any research reactor contains a critical mass of fuel, and therefore is fully capable of meltdown.
https://ne.oregonstate.edu/11-mw-triga-mark-ii-pulsing-resea...
As far as meltdown: if you drain all of the water, they do not generate enough decay heat to melt down due to their size.
They were invented by Freeman Dyson as a "reactor safe enough for high school students to operate".
Typically there is a person whose name is on the license, who is responsible for the proper use of the reactor. At an organization this could be the boss, owner, or RSO. In theory, as a private citizen you could get a license, as long as you can prove to the regulator that you have the experience and training to operate the reactor properly.
Of course, you would have to comply with all the rules and regulations. This could be quite burdensome for a private citizen, especially with the additional security rules added post 9/11 (assuming you are not a billionaire).
Edit: removed link to quantities of concern, sorry, rules are different for reactors.
Edit again: better link for security regs: https://www.nrc.gov/reactors/non-power.html
In Moscow (Russia) alone, there are nearly a dozen of research reactors, of various designs.
There are 200+ decommissioned experimental reactors, 240 operational, 200 shut down, and a few others in change. The more interesting thing is the variety, 70+ types, 20+ types of moderators, 80+ types of control rods, 20-ish types of coolants, 50+ types of reflector materials.
Edit: here's a full list of types and their counts.
+----------+---------------------------+
| count(*) | technical_21_reactor_type |
+----------+---------------------------+
| 4 | NULL |
| 3 | AIR COOLED |
| 1 | AQUEOUS BREEDER |
| 28 | ARGONAUT |
| 1 | BWR |
| 1 | BWR POWER |
| 2 | BWR-PROTOTYPE |
| 97 | CRIT ASSEMBLY |
| 9 | CRIT FAST |
| 1 | CRIT GRAPHITE |
| 3 | EXPERIMENTAL |
| 3 | FAST |
| 8 | FAST BREEDER |
| 9 | FAST BURST |
| 1 | FAST SOURCE |
| 2 | FAST, HG COOLED |
| 2 | FAST, NA COOLED |
| 1 | FAST, POWER |
| 1 | FAST, PULSED |
| 1 | GAS |
| 12 | GRAPHITE |
| 2 | GRAPHITE AGR |
| 2 | GRAPHITE CO2 |
| 4 | GRAPHITE PILE |
| 1 | GRAPHITE, AIR |
| 1 | GRAPHITE, PULSE |
| 1 | HE COOLED |
| 2 | HEATING PROT |
| 35 | HEAVY WATER |
| 1 | HEAVY WATER PWR |
| 2 | HIGH TEMP GAS |
| 3 | HOMOG |
| 28 | HOMOG (L) |
| 41 | HOMOG (S) |
| 2 | HOMOG PUL |
| 1 | LOOP TYPE |
| 9 | MNSR |
| 1 | MOBILE EDU. |
| 1 | N2 COOLED |
| 1 | ORGANIC MODER |
| 134 | POOL |
| 1 | POOL-2 CORES |
| 1 | POOL-VAR |
| 10 | POOL, IRT |
| 3 | POOL, MTR |
| 2 | POOL, PULSTAR |
| 1 | POOL, UZRH |
| 1 | POOL/CHANNELS |
| 1 | PRESS. VESSEL |
| 1 | PRESSURIZED |
| 9 | PROMPT BURST |
| 4 | PULSING |
| 3 | PWR |
| 1 | PWR POWER |
| 1 | PWR PROPULSION |
| 3 | SLOWPOKE |
| 7 | SLOWPOKE-2 |
| 1 | SPACE TEST |
| 12 | SUBCRIT |
| 56 | TANK |
| 10 | TANK IN POOL |
| 11 | TANK WWR |
| 2 | TRIGA |
| 2 | TRIGA ACPR |
| 8 | TRIGA CONV |
| 2 | TRIGA DUAL CORE |
| 1 | TRIGA MARK CONV |
| 3 | TRIGA MARK F |
| 20 | TRIGA MARK I |
| 24 | TRIGA MARK II |
| 6 | TRIGA MARK III |
| 1 | TRIGA MODIFIED |
| 1 | U-233 FUELLED |
| 1 | ZERO POWER D2O |
| 1 | ZERO POWER HTD |
| 1 | ZRH, AIR COOLED |
| 1 | ZRH, BE REFLECT |
| 1 | ZRH, H2O COOLED |
+----------+---------------------------+