In.

Demineralized water is commonly used as cooling water, neutron moderator and as a radiation shield in a nuclear reactor such as Bandung Triga 2000 Reactor. According to its function, demineralized water has to fulfilled some requirements as stated in Safety Analysis Report (SAR) of Bandung Triga 2000 Reactor. The requirements were impurities of Ca, Na and Mg, pH and conductivity electricity in demineralized water reactor. Determination of Ca, Na and Mg as impurities were carried out using Flame Atomic Absorption Spectrophotometry (FAAS). In this activity, instrument and method verification were carried out as quality control. Instrument verification determined were sensitivity, precision and detection limit of FAAS. Method verification was carried out by using spike demineralized water with Na, Ca, and Mg standard. Accuracy and precision of the method were in the acceptance criteria according to AOAC then implemented to determined impurities of Ca, NA, Mg in demineralized water reactor samples. Na and Mg in demineralized water using FAAS gave values less than 1 mg/L, pH values were in the range 5,5- 6,5 meanwhile conductivity electricity gave values were less than 3 µmho fulfilled the requirements in SAR. These results were indispensable to support the performance of Bandung Triga 2000 Reactor which needed by public and university for the development of science and its application in the industry, health, environment and other fields.