Analytical estimation of accessibility to the activated lithium loop in IFMIF

Beryllium-7 (7Be) is the dominant nuclide affecting accessibility and maintenance scenario of the lithium loop of the International Fusion Materials Irradiation Facility. The dose equivalent rate around typical components of the lithium loop was calculated employing a code QAD-CGGP2R. Deposition of 7Be on the components was assumed to be proportional to their surface area wetted by liquid lithium. As result, the most severe condition was around the heat exchanger with surface area of 576 m2. The dose equivalent rate was about 107 μSv/h, several orders of magnitude higher than 10 μSv/h limit considering ICRP recommendation. The dose rate can be reduced below the limit by a 22 cm-thick iron shield or a 6.5 cm-thick lead shield. Also, a possible method of reduction of the dose rate and the shield thickness by employing a cold trap was shown.