Preliminary neutronic studies for the liquid-salt-cooled very hightemperature reactor (LS-VHTR).

Evaluation of the DRAGON code for VHTR design analysis.

“…[5] The MCNP4C calculations for the fuel assembly were performed using the ENDF/B-VI nuclear data library distributed with the code. In the DRAGON and WIMS8 calculations, the 172 group transport equations were solved.…”

“…A lithium enrichment value of 99.995% (Li-7 content) is used. [5] Results from the study are summarized in Tables 3 and 4. In addition to the traditional element eigenvalue, an estimate of the double heterogeneity effect was also obtained.…”

Neutronic assessment of stringer fuel assembly design for liquid-salt-cooledvery high temperature reactor (LS-VHTR).

“…In order to represent the whole-core state adequately with an assembly-level calculation, the effect of neutron leakage through the core boundary must be accounted for in the assembly k inf value. The FY 2005 study [1] indicated that the LRM gives a good estimate of the LS-VHTR reactivity letdown when an appropriate core leakage approximation is utilized. That study indicated that the LS-VHTR neutron leakage is a reactivity penalty of ~ 1 to 2% ∆k.…”

“…[1,2] Earlier project studies had indicated that the LS-VHTR designs using fuel blocks similar to those employed for the Fort Saint Vrain and GT-MHR cores could result in the blocks floating during refueling. [3] This is because of the lower density of the fuel block relative to the liquid salt coolant.…”

“…The target values for the fuel discharge burnup and cycle length that were used in the FY 2005 study [1] have been retained. Specifically, the discharge burnup and cycle length should be at least 100 GWd/t and 1-½ years, respectively, with the uranium enrichment constrained to less than 20% 235 U.…”