No moving parts
The novel feature of the reactor is that the boiler temperature, and thus the power output, is kept steady without the need for any moving parts, flowing water or human intervention. If the thermal load is removed, the uranium hydride goes over temperature, the hydrogen is driven out of the uranium metal and the chain reaction will eventually come to a stop, causing the reactor to cool off until it returns to its temperature set-point. Since the system is sealed, the hydrogen will eventually flow back into the uranium core when it has cooled sufficiently, causing the reaction to restart. The up-shot is that the temperature and thus concentration of hydrogen will stabilize at a factory pre-set temperature, although if the sealed core is breached for any reason, the hydrogen will escape causing the fission to permanently stop.

Heat from the reaction is removed by liquid metal flowing in pipes with mesh wicks. According to the company, these sealed systems are about 1000 times [?] better than solid metals in transferring heat. Using these pipes is also an important safety feature because they keep water, which can act as a moderator and slow down the neutrons (thereby speeding up the chain reaction), well away from the reactor core.  [Water in Ft St Vrain's TRISO prism core was a recurring problem.  A reason for the interest in TRISO helium or nitrogen gas turbine systems.]

 

Chinese HTR-PM 100 MWe, TRISO Pebble (No English contact)  Chinese Pebble Bed Reactor Progress - May 2007.pdf 

Active.  Designed to be connected in parallel with a second HTR-PM to produce steam for a conventional 200 MWe coal power plant turbine.

Dr. Andrew Kadak at MIT is knowledgeable about the Chinese TRISO reactor program.  http://web.mit.edu/pebble-bed/contact.html   http://web.mit.edu/pebble-bed/