Nuclear Power Related Media Thread, page-6219

RR & Terrapower are very different reactors (SMR's) with very different fuel needs.

The RR reactors (see HERE) is just a conventional pressurized water reactor (PWR) which is what Framatome and Westinghouse and others have been building for years (also RR for Royal Navy subs). Like their competitors the modularization of these reactors does not represent a major challenge (it's being done now for the GEN3+ reactors and also in naval reactors. The SMR's will use conventional LEU fuel (~4.8% enrichment) - naval reactors (apart from France use HEU - 93% enrichment - military only - it's weapons material). From fuel producers standpoint much the same as now but adds to demand. Should be in production by the end of this decade. The challenge is that the RR SMR is that it is not drastically different to a lot of other SMR (just a bit bigger - 470Mw). As a "conventional" operation it should not have too many hold up (but beware the UK regulator can be pedantic - 7,000 deign changes were required for the Framatome design currently being installed at Hinkley point (see HERE)) - thus the massive cost overruns) It will have all the issues of PWR's which are:

a) operate at high pressure (~150 bar) and lower temperature (300C) steam (thus lower efficiency turbines) - turbine efficiency goes up with steam temperature. High pressures also mean that it can explode (not nuclear). The turbines are driven from a secondary circuit through a "steam generator" - heat exchanger
b) Not good at ramping (you can put boron compounds in the primary steam circuit but this is slow).
c) Poor (compared to fast reactor) fuel usage & more HL waste - lower burn of higher actinides (Pu, Ce Np etc) and lower fission of 238U (but some due to neutron capture and transmutation to Pu) & leaves 236U (nuclear poison) in that HL waste. The HL waste is about 1% 235U and higher actinides - long half lives - 100k - millions of years but not particularly dangerous levels/types - low gamma) - most radioactivity goes in about 400 years

Advantages are
a) known problems and solutions
b) transparent coolant (water) - you can see your way when something is wrong
c) Uses thermal (slowed down neutrons) ltra safe

The Terrapower (also GEH) Natrium (latin for Sodium) reactor (see HERE) is IMO a "breakthrough" it uses Sodium (actually a Sodium/Potassium eutectic) as coolant and operates at atmospheric pressure (it can't blow up from pressure) but is a "fast" reactor which uses fast nuetron (they are not slowed down by a moderator - water in the case of a PWR). This implies much higher assays of 235U (or 233U or Pu) and means the fuel has to be enriched to ~20% 235U (and burns down to about 6% 235U).

Disadvantages are:

a) relatively unknown technology - mainly the EBR-II which ran for 20 years - closed in 1994 by Jimmy Carter. Problems with Japanese & French sodium reactors (sodium fires - particularly with water). Issues with the regulator in going to new design (NRC (USA) particularly bad)
b) The coolant (sodium) is opaque
c) sodium fizzles in air and explodes in water (water must be kept far from it)
d) safety unproven - tests on EBR-II were good and showed intrinsically safe but doubts about tests being "staged". Reactor safety principle appears sound (nuclear Doppler shift) - nuclear physics says that as temperature goes up fission should slow & stop)
d) needs HALEU (19.75% 235U) as uranium metal fuel - special fabrication currently being developed by Global Nuclear fuel (GNF) on the same site in Wilmington as is the GLE test loop (Castle Haynes)
e) the waste has higher level (~6%) 235U still left in it (possibly could be re-processed to thermal nuclear fuel for RR and other BWR/PWR thermal reactors)

Advantages are:

a) the Natrium has a "Nuclear" (nuclear safety critical) and "thermal" part (only steam/turbine safety critical. The nuclear part is a "fast reactor" and has to go through the NRC - the "thermal" part is molten salt bath & heat exchanger/conventional steam turbines. There are "regulation" advantages but the big one is that the reactor can operate at a constant 345Mw and the "themal" system (molten salt) can be used for storage allowing the nominal 345 Mw to be flexed between 100Mw (at high renewable supply) to 500Mw (at low renewable supply). The fuel usage is good since the "nuclear" bit operates at a constant 345Mw - giving excellent fuel usage
b) since it's a fast reactor it burns the higher actinides (long half life waste) and 236U nuclear poison, transmutes more 238U to Pu (which fissions). The fuel efficiency (burn up) should be better than a thermal reactor
c) the HL waste should contain less long half life higher actinides & since fuel efficiency is better less HL waste
d) Terrapower are forecasting build times of 36 months

This is really a large topic but from a fuel standpoint we should be able to provide UF6 for fabrication at the require enrichment level for the RR reactor (opportunity 2) - it will need to be deconverted (turned into UO2) and fabricated into fuel elements (GNF/Westingouse/Framatone etc). Opportunity 3 is HALEU (20%) IMO we are less competitive in this area but LEU (5%) fuel is still required as feedstock for HALEU.