The catalytic conversion of tritium gas (HT) to tritiated water (HTO)
by cement materials is studied by using mortars made of ordinary Portl
and cement and Portland blast furnace slag cement exposed to HT at con
centrations of 3 to 6 x 10(9) Bq/m(3) in air. Within the experimental
conditions, no significant difference in the conversion rate is found
between the two types of cement. Extended experiments are carried out
by using mortars made of ordinary Portland cement to evaluate the cata
lytic effect of cement materials. The experimental results are explain
ed by a model that assumes that the conversion is dependent on the geo
metric surface area of the mortars. The mortar surface is found to pla
y an important role in the conversion. The capacity coefficient in mas
s transfer on the mortar surface and its standard deviation are found
to be (4.3 +/- 1.4) x 10(-11) m/s. The mechanism of the conversion rea
ction is uncertain in this study. The conversion rate of the catalytic
effect by the cement materials is compared with the conversion rate b
y the radioactive decay of T-2 The HTO produced by the conversion is r
etained in the pore water of the cement materials.