The assessment of the neutron activation of corrosion products generated in one year of IFMIF lithium loop operation due to the interaction between lithium and Stainless Steel SS-304 was performed. The study was accomplished through the following phases: 1. neutron spectrum calculation in the lithium target via MCNP-4C2 with McEnea neutron source model; 2. evaluation of inventories and decay gamma sources production via ANITA-IEAF activation code package; the calculations were performed by considering a lithium mix composition containing lithium impurities and corrosion products referred to 200 wppm of Steel SS-304 corresponding to a corrosion rate of 0.2 µm/y and a SS-304 wetted surface of 572 m2 ; an irradiation scenario reproducing the integrated (in eleven months of operation) neutron flux responsible for the activation of the circulating corrosion products facing the deuteron beam was considered; 3. decay gamma transport analysis for dose rate evaluations via both VITENEA-IEF/SCALENEA-1 and MCNP-4C2 systems for the Longest Pipe of the Lithium loop . The following conclusions can be drawn: • dose rates, due to the presence of activated corrosion products, at 50 cm from the Longest Pipe are 198µSv/h and 85µSv/h at 1 day and 1 week from the plant shutdown, respectively • considering the average of 20 mSv/a as the limit in Europe for “Radiation Worker” and the four-week period of annual maintenance activities in Li loop, the zone around the Li piping, exceeding 125 mSv/h, has to be declared “Restricted Access Area” • the worker radiation protection could be a concern for IFMIF if a good purification system of Li will not continuously run • specific procedures and worker protection equipments (such as Remote Handling tools) and shielding have to be considered to maintain the Li loop. Sensitivity analyses have also been performed to evaluate the impact on results of the choice of different neutron source models, of irradiation scenarios and of corrosion rates/lithium mix composition on the dose rates.
Neutron induced activation of the IFMIF lithium loop (gamma decay sources and dose rate estimates) / D.G. Cepraga; T. Pinna; M. Frisoni; G. Cambi. - STAMPA. - (2005).
Neutron induced activation of the IFMIF lithium loop (gamma decay sources and dose rate estimates)
CAMBI, GILIO
2005
Abstract
The assessment of the neutron activation of corrosion products generated in one year of IFMIF lithium loop operation due to the interaction between lithium and Stainless Steel SS-304 was performed. The study was accomplished through the following phases: 1. neutron spectrum calculation in the lithium target via MCNP-4C2 with McEnea neutron source model; 2. evaluation of inventories and decay gamma sources production via ANITA-IEAF activation code package; the calculations were performed by considering a lithium mix composition containing lithium impurities and corrosion products referred to 200 wppm of Steel SS-304 corresponding to a corrosion rate of 0.2 µm/y and a SS-304 wetted surface of 572 m2 ; an irradiation scenario reproducing the integrated (in eleven months of operation) neutron flux responsible for the activation of the circulating corrosion products facing the deuteron beam was considered; 3. decay gamma transport analysis for dose rate evaluations via both VITENEA-IEF/SCALENEA-1 and MCNP-4C2 systems for the Longest Pipe of the Lithium loop . The following conclusions can be drawn: • dose rates, due to the presence of activated corrosion products, at 50 cm from the Longest Pipe are 198µSv/h and 85µSv/h at 1 day and 1 week from the plant shutdown, respectively • considering the average of 20 mSv/a as the limit in Europe for “Radiation Worker” and the four-week period of annual maintenance activities in Li loop, the zone around the Li piping, exceeding 125 mSv/h, has to be declared “Restricted Access Area” • the worker radiation protection could be a concern for IFMIF if a good purification system of Li will not continuously run • specific procedures and worker protection equipments (such as Remote Handling tools) and shielding have to be considered to maintain the Li loop. Sensitivity analyses have also been performed to evaluate the impact on results of the choice of different neutron source models, of irradiation scenarios and of corrosion rates/lithium mix composition on the dose rates.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
