Využití thoria v palivovém cyklu pokročilých jaderných reaktorů

Abstract

Cinsky vysokoteplotni plynem chlazeny reaktor HTR-PM bude brzy uveden do provozu. Jakozto reaktor s gra?tovym kulovym lozem nabizi HTR-PM sirokou skalu moznosti pri navrhu palivoveho cyklu. Reaktor byl navrzen pro pouziti s obohacenym uranovym palivem, jelikoz jde ale o tepelny gra?tem moderovany system, nabizi se moznost vyuziti thoria jako mnoziveho ma-terialu. V teto diplomove praci bude vyuziti thoria zkoumano na trech urovnich - na urovni uzavreneho rovnovazneho cyklu, otevreneho rovnovazneho cyklu a na urovni pocatecni palivove vsazky a prechodove faze k rovnovaznemu cyklu. Hlavnim cilem je zhodnotit, zda pridani thoria muze zlepsit udrzitelnost provozu reaktoru skrze zvysene vyuziti prirodnich zdroju. Pro zkoumani palivovych cyklu byly pouzity tri softwarove nastroje. Monte Carlo kod Serpent 2 byl vyuzit predevsim k zhodnoceni rovnovazneho otevreneho cyklu. Procedura EQL0D vyv-inuta B. Hombourgerem a postavena na Serpentu 2 byla vyuzita pri vysetrovani uzavreneho rovnovazneho cyklu. V neposledni rade, nove vyvinuta procedura ScRB, taktez zalozena na Serpentu 2, byla pouzita k zhodnoceni pocatecnich palivovych vsazek a prechodovych fazi k rovnovaznemu cyklu. Podrobna analyza uzavreneho rovnovazneho cyklu potvrdila jeho neproveditelnost. Vysledky ziskane pri analyze otevreneho rovnovazneho cyklu naznacuji moznost pozitivniho efektu thoria na udrzitelnost tohoto cyklu, je vsak nutne podrobnejsi zhodnoceni. Byla potvrzena proveditelnost smisene pocatecni vsazky s thoriem a obohacenym uranem. Nicmene prinosy takoveho reseni jsou diskutabilni.

The construction of the Chinese HTR-PM reactor, a representative of Gen. IV VHTR class, is in its ?nal stage. As a pebble-bed reactor, HTR-PM o?ers a great freedom for fuel cycle design thanks to continuous recirculation of pebbles through the core. The reactor was designed to utilize low enriched uranium fuel. However, since HTR-PM is a thermal graphite-moderated system, there might be an opportunity to utilize thorium as a fertile material. In this thesis, the utilization of mixed LEU-Th fuel will be investigated at three levels - in an equilibrium closed fuel cycle, equilibrium open fuel cycle, and in an initial core and a running-in phase of reactor operation. The main goal is to evaluate, whether addition of thorium can improve sustainability of the reactor through increased utilization of natural resources. Three software tools were used for the fuel cycle investigations. Monte Carlo code Serpent 2 was used mainly for evaluation of the equilibrium open fuel cycle. EQL0D, a Serpent 2 based procedure developed by B. Hombourger, was used for evaluation of the equilibrium closed fuel cycle. Last but not least, a new Serpent 2 based Semi-continuous Refueling Burnup (ScRB) routine was developed for the purpose of evaluation of di?erent initial cores and running-in phases of operation. Analysis of the closed equilibrium cycle con?rmed its infeasibility. Results obtained for the equilibrium open cycle suggest a chance of positive contribution of thorium towards the sustainability of the cycle, although further analyses are still needed. The feasibility of a mixed LEU-Th initial core was proved, however the bene?ts of such design are questionable.