Dose rates calculated in the air for the internal structures taken off from the WWR-S IFIN-HH reactor

Following the proposed strategy (IAEA Stage 2) of the decommissioning of the WWR-S IFIN-HH reactor, the most part of the reactor tank will remain in place, except some internal structures, which will be extracted. The topic of this work consists in the computational determination, using MERCURE-3 code, of the dose rates, in the air, arisen from the internal items which could be taken off from the reactor, namely: some leading pipes, the separator assembly, the vessel assembly and the rings of the iron shielding. The calculation models elaborated and the approximations made are done taken into account the manner in which these items are welded and how they could be dismantled and extracted from the reactor and handled after that. Gamma sources accumulated in the reactor were calculated, with ORIGEN code based on the neutron flux obtained from a two-dimensional calculation using TWOTRAN program. A reference time of 100 days after reactor shutdown was considered. Resulted dose rates on the surface of the items, and respectively: surface +20cm, +100cm, +200cm, +800cm, +1000cm are tabulated into the paper. Qualitative comparison with the measured values on other WWR-S reactors is done. The obtained results supply information regarding the conditions of personnel operation in the working area and assist to the achievement of the working procedures that must be observed during the decommissioning activities, to assure the safety of staff upon the ALARA principles. (author)