Three-dimensional reactor pressure vessel fast neutron fluence calculations for the AP600 using TORT

The results of a study are described focusing on a comparison of the values of fast neutron fluence for the AP600 reactor pressure vessel, calculated in 3-D with two different libraries: SAILOR (ENDF/B-IV) and BUGLE-93 (ENDF/B-VI). The presence of a radial reflector composed of stainless steel has been accounted for. Besides the 3-D core and internals representation allow the emergence of a more accurate relationship between the specimens and the inner vessel fluence. The availability of a CRAY computer in FINMECCANICA makes the three-dimensional transport code TORT an attractive choice. The analysis confirms that for the presence of the stainless steel radial reflector in the AP600 the use of the BUGLE-93 library implies a more conservative estimation (about + 10%) of the pressure vessel neutron fluence with respect to the use of the SAILOR library. (R.P.)