Abstract: Two dominant building materials of coral sand and coral skeleton were measured using high purity germanium γ spectrometry with high energy resolution for the first time. The activities of ²³⁸U, ²²⁶Ra, ²²⁸Ra, ⁴⁰K in coral sand and coral skeleton were 24.8 Bq/kg, 2.38 Bq/kg, 2.10 Bq/kg, 11.6 Bq/kg and 28.7 Bq/kg, 3.47 Bq/kg, 12.6 Bq/kg, 10.9 Bq/kg, respectively. The radioactive level of coral sand and coral skeleton was 1%-10% of the recommended value and limiting value provided by the international organizations. After comparison of radioactivity in a variety of building materials, we found that coral sand and coral skeleton had the lowest radioactive level. These building materials of low radioactivity can be potentially used in the construction of the low radioactive laboratory and used as dilution to reduce radioactivity during the production of building materials (coal ash) with high radioactivity.

Key words: radionuclide, reef engineering, building material, coral, coal ash, low radioactivity laboratory