The Provisional Technical Secretariat of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) Organization has established the International Monitoring System (IMS) under its auspices. Through technological advances, the CTBT has achieved nuclear test detection limits of 1 kiloton by the use of CTBT verification technologies. However, radionuclides were not observed clearly by the IMS during the first and second nuclear weapon tests conducted by the Democratic People’s Republic of Korea (DPRK). With the third test carried out by the DPRK, however, they could observe traces of the event using the IMS, noble gas detection stations, and Atmospheric Transport Modeling (ATM) techniques. After the accident at the Fukushima Dai-ichi Nuclear Power Plant in March 2011, the IMS accurately tracked the global movement of radionuclides that originated from this event. In the following report, the current situation and recent problems regarding environmental monitoring of radionuclides by the CTBT are presented and discussed. Focus will be placed on the detection abilities of the IMS and the system used for evaluation of the radionuclides released by nuclear explosions and power plant accidents.

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Cerium(IV) tellurium molybdate was prepared as a new gel bed for chromatographic ⁹⁹Mo/^99mTc generator. The gel material prepared with the optimum conditions was characterized with IR spectroscopy, thermal analysis, XRD, EDX and FESEM. The highest precipitation yield of ⁹⁹Mo within the formed gel was found to be 97.6 % at a Ce:Te:Mo molar ratio of 1:0.2:1. The prepared ⁹⁹Mo/^99mTc chromatographic column based on Ce(IV) tellurium molybdate gel bed showed a good performance. The ^99mTc elution yield was 77.8±3.0 % with a radionuclidic purity of ≥ 99.99 %, radiochemical purity of 96.5±1.3 % (as ^99mTcO₄^-) and pH-value in the range of 5-7. Molybdenum and cerium levels in ^99mTc eluates did not exceed 1 and 0.3 ppm, respectively, while no tellurium was detected.

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