Piyush Ojha Jan 23, 2017:

Perhaps the text should read 'high intercrystalline-strength grout caps', i.e. the flat roofs are capped with grout that has high intercrystalline strength. The main ingredients of Portland cement are crystalline and the crystals are held together, it seems, by some kind of gel. The term 'intercrystalline strength' now makes sense: if it is high, the material is less likely to crack.

Piyush Ojha Jan 23, 2017:

Cement-based grouts with additives to ensure appropriate flow, set and reaction characteristics are used for nuclear entombment. In capping a flat roof with grout, I think it would be necessary that the grout flows into minute cracks and seals them. The term 'intercrystalline grout caps' suggests that the grout is formulated to flow into intercrystalline spaces but it doesn't make sense to me because I don't see the flat roof being made of crystalline materials. I wonder if there has been a mistranslation from Japanese.

Masoud Kakouli Varnousfaderani (asker) Jan 22, 2017:

More context: Under exceptional circumstances, entombment may also be considered as the ultimate decommissioning end state. Entombment involves encasing the facility in a long lived material to make sure that residual radioactivity cannot migrate to the environment. To date, this technique has been used on a smaller scale for research test reactors and most recently on a large scale for former nuclear material production reactors in the United States. In 2011, the Department of Energy completed the entombment of two former nuclear material production reactors at the Savannah River Site. In both instances, all fuel was removed, and the below grade sections of the facility were filled with cementious grout. The above grade structures, built of reinforced concrete, were left in place. To restrict rainwater intrusion, high strength intercrystalline grout caps were installed on the flat roofs 91 above the production areas. The Department of Energy is also deploying entombment as a decommissioning strategy