The possibility of liquidating irradiated graphite by burning is examined by analyzing the computed and experimentally obtained information about the activity of 14 C produced over the period of operation of uranium-graphite reactors and appearing naturally in the Earth's biosphere. In nature, 14 C activity fluctuates in the range ±1%. This work employs the criterion that the technogenic addition of 14 C activity as a result of burning irradiated graphite should not exceed the fluctuations of the natural activity. It is shown that under this criterion an amount ~3.5·10 4 tons/yr can be burned with 14 C activity in irradiated graphite ~1.8·10 11 Bq/ton.Channel-type reactors containing a large mass of graphite moderator (from 1000 to 2500 tons) comprise a substantial part of the nuclear power-generating units in the world. Many of these first-generation reactors have operated for more than 30 yr and have been shut down. A common feature of the decommissioning of all these reactors is a radiation-safe technology for handling irradiated graphite, present in a neutron field whose fluence reached ~3.5·10 22 cm -2 [1]. Neutron irradiation resulted in the formation in the graphite of long-lived products of activation of carbon and elements present in the form of impurities in carbon. Accidents in which nonremovable fuel spills which contain actinides and fission products and enter the graphite masonry have occured during the operation of power-generating units.Burning the irradiated graphite is the most attractive method. It has already been tested in France on a low-capacity experimental facility (hundreds of t/yr). However, the following factors prevent wide adoption of the method:• atmospheric emissions of CO 2 with isotopic ratio 14 C/ 12 C which is 10 6 times greater than that found in nature;• the amount of irradiated graphite in the world is large (>100,000 tons); • the requirements mandating the elimination of risk due to all radionuclides are stringent. The first factor is the main reason. Therefore, it merits a separate analysis. The only alternative to burning is storage, for example, in storage facilities located on the ground and isolated from the environment, permitting observation of and intervention in the conditions of storage. There are also realistic prospects for variant where the irradiated graphite is buried permanently, taking account of the fact that graphite will maintain itself except under extreme conditions.
Lack of geological and tectonical knowledge in a region causes hazard in project implementation. There are many examples related to this issue in Iran and the world. Main purpose of this research is to analyze the fractures because of their importance and effect on the implementation of engineering and civil engineering projects such as Khansar-Boien Miyandasht tunnel. For this purpose, the process and density of the fractures and their spatial-geometric position were investigated. Therefore, joints and faults in the Khansar syncline area and the site of Khansar-Boien Miyandasht tunnel were collected, then processed by interpreted in the software such as Stereo32 and Georient. According to the result, a group of joints can be related to pre-tectonics, another one can be related to syn-tectonics(folding and faulting) and some fractures are related to the post-tectonics . Geomechanically, syn-tectonic fractures are extensive in depth and these issues are very important, so it should be considered in implementing the project of Khansar tunnel. Results of the geological engineering study such as, uniaxial strength test, point loading, Schmidt hammer, and ultra-sonic Test were showed high-resistance massive orbitolina limestone , and alternation of shale , limestone , medium-resistance limestone and black slates include low resistance that lead to apply the supports with higher safety factor. Considering the tunnel direction (NNE-SSW), high slope fractures and tunnel tensions, it is possible to create sliding wedges in the left wall and left ceiling of the tunnel. Therefore, tunnel drilling should be performed cautiously by blasting method.
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