Comprehensive Nuclear-Test-Ban Treaty Organization Research Articles

Atmospheric xenon radioactive isotope monitoring

The Comprehensive Nuclear Test Ban Treaty (CTBT) organisation is implementing a world-wide monitoring network in order to check that the State Signatories comply with the treaty. One of the monitoring facilities consists of an atmospheric noble gas monitoring equipment. According to the requirements annexed in the treaty, the French Atomic Energy Commission (CEA) developed a device, called SPALAX TM, which automatically extracts xenon from ambient air and makes in situ measurements of the activities of four xenon radioisotopes ( 131mXe, 133mXe, 133Xe, 135Xe). The originality of this device is noticeable essentially in the gas sample processing method: thanks to the coupling of a gas permeator and of a noble gas specific adsorbent, it can selectively extract and concentrate xenon to more than 3×10 E 6. This process is carried out continuously without cryogenic cooling, without any regeneration time. The detection of the xenon radioactive isotopes is done automatically by high spectral resolution γ spectrometry, a robust technology well-suited for on-field instrumentation. In the year 2000, a prototype was involved in an international evaluation exercise directed by the CTBT organisation (CTBTO). This exercise demonstrated that the SPALAX TM equipment perfectly met the requirements of the CTBTO for such systems. On the basis of the continuous 24-h resolution record of the atmospheric xenon radioactive isotopes concentrations, the SPALAX TM system also demonstrated that ambient levels of 133Xe can fluctuate quickly from less than the detection limit to over 40×10 −3 Bq m −3. In order to build an industrial version of this equipment, the CEA entered into a partnership with a French engineering company (S.F.I., Marseille, France), which is now able to produce an industrial version of SPALAX TM, i.e. more compact and more efficient than the prototypes. The 133Xe minimum detectable concentration is 0.15×10 −3 Bq m −3 air per 24 h sampling cycle.

Four decades of progress in seismic identification help verify the CTBT

How well a Comprehensive Nuclear Test Ban Treaty (CTBT) can be verified has been debated for many decades. Verification was of major contention in 1999 during the U.S. Senate debate on ratification. Then‐governor George Bush claimed in 2000 and again in 2002 as president that the treaty, which the U.S. signed in 1996, is not verifiable. Since 1995, the international CTBT Organization focused on detecting and locating globally many small seismic events. While its staff filters out many obvious earthquakes, the identification of nuclear explosions and problem seismic events is reserved for national CTBT agencies. Since the findings of national authorities typically are classified, it is difficult to ascertain how well seismic events can be identified. Nevertheless, only a tiny fraction of events detected over the past 42 years were singled out in unclassified scientific and governmental documents or the media as problem events whose identification potentially compromises the verifiability of a CTBT.

Hydroacoustic station network for monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT)

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) provides for monitoring of the whole globe by a network of stations, using various technologies, in order to verify the absence of nuclear explosion tests. The hydroacoustic component of this network, which monitors the major world oceans, is currently under construction. When complete it will consist of 11 stations located with an emphasis on the vast ocean areas of the Southern Hemisphere. Presently, three stations have been completed and work is underway on all of the remaining stations. The stations transmit real-time continuous data to the CTBT Organization headquarters in Vienna, Austria. The hydroacoustic network uses two different types of stations. One type is based on hydrophones floated from the sea floor to the SOFAR axis depth, arranged horizontally in a triplet configuration. The other type is based on the use of seismometers located on small islands to detect hydroacoustic signals after conversion to seismic signals at the flanks of the island. During the time since completing the first stations, many interesting acoustical phenomena have been observed in the data.

The IMS Belbasi Seismic Array (BRAR) in Central Turkey

In this paper we give detailed station specifications as well as a preliminary study of the S -wave velocity structure beneath the Belbasi seismic array. The Belbasi seismic array is one of the first seismic arrays in the world; it was established in 1951 in the Belbasi suburb of the city of Ankara in central Turkey. This array had been jointly operated by the Turkish General Command (TGC) and the Air Force Technical Application Center (AFTAC) of the USA until February 2000. Recently, Bogazici University Kandilli Observatory and Earthquake Research Institute (KOERI) took over the operation of this array. In the near future, the entire array will be relocated to the town of Keskin, about 120 km east of the present location. This new array will be a primary seismic station of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). In addition to this short-period array in Keskin, a new long-period array and one broadband station will be deployed around the city of Ankara. Despite its new location, the entire array, including broadband, short-period, and new long-period stations, will still be named the Belbasi array but with the station code of BRTR. Turkey, where the array is located, and the surrounding regions are seismically active and rapidly deforming and are characterized by high seismic wave attenuation in the crust ( Lg ) and uppermost mantle ( Sn ). The high attenuation of the regional seismic waves and the relatively sparse IMS station distribution in the region combine to lessen the detection capabilities in the area. This makes it essential that effective seismic arrays are deployed in the Middle East. Furthermore, the event location capabilities of the IMS have been selected as one of the major research priorities by the Preparatory Commission for the CTBTO. Data collected …