Radioactive inventory

A first attempt to estimate the potential consequences from severe LWRs accidents was the BNL report WASH-740 (1957). The authors of WASH-740, to overcome the lack of information and methods, estimated "Hazard States based on the core state, radioactive inventory, fuel cladding, reactor coolant system, and containment conditions. 

Liquid metal walls in ICF reactors will become contaminated with target debris. In addition to posing compatibility problems, these contaminants affect pumping power, pump life, and radioactive inventory. Thus, methods of removing contaminants, particularly high-Z elements, from liquid lithium are required. For example, no economical method to remove Pb to below 1 a/o (23 w/o) in Li has been devised. 

Compared with fission reactors, operation of fusion reactors is more complicated because of the high ignition temperatures, the necessity to confine the plasma, and problems with the construction materials. On the other hand, the radioactive inventory of fusion reactors is appreciably smaller. Fission products are not formed and actinides are absent. The radioactivity in fission reactors is given by the tritium and the activation products produced in the construction materials. This simplifies the waste problems considerably. Development of thermonuclear reactors based on the D-D reaction would reduce the radioactive inventory even further, because T would not be needed. The fact that the energy produced by fusion of the D atoms contained in 1 litre of water corresponds to the energy obtained by burning 120 kg coal is very attractive. 

In any case, the primordial radioactivity on the earth was appreciably higher than at present. The ratios of the aetivities at the time of the birth of the earth to those at present are listed in Table 15.4 for some long-lived radionuclides that represent the main radioactive inventory on the earth. The relatively high activity of about 2 10 y ago is the reason for the operation of the natural nuclear reactors at Oklo at that time (seetion 11.8). 

Nuclear reactors and reprocessing plants are constructed and operated in such a way that the radioactive inventory is confined to shielded places. Only limited amounts of radionuclides are allowed to enter the environment. The amounts of T and produced in nuclear reactors vary with the reactor type, between about 10 and 10 Bq of T and about lO Bq of per GWg per year. Tritium is released as HTO and about one-third of the is in the form of " C02. Under normal operating conditions, very small amounts of fission products and radioelements are set free from nuclear reactors and reprocessing plants. In this context, the actinides and long-lived fission products, such as °Sr, Tc, I, and Cs, are of greatest importance. 

Despite the safety regulations, accidents have occurred with nuclear reactors and reprocessing plants, primarily due to mistakes of the operators. By these accidents parts of the radioactive inventory have entered the environment. Mainly gaseous fission products and aerosols have been emitted, but solutions have also been given off. In the Chernobyl accident, gaseous fission products and aerosols were transported through the air over large distances. Even molten particles from the reactor core were carried with the air over distances of several hundred kilometres. 

Of particular relevance is the inherent hazard represented by the radioactive inventory of the waste and is the summed product of the activity (Bq) of each radionuclide present and its corresponding Specific Instantaneous Toxic Potential (SITP). This can be adjusted for decay for longer timescales and it is usual to employ the full radionuclide inventory for waste streams as sampled and quantified by Magnox Electric Ltd and reported in the U.K. Radioactive Waste Inventory. ... 

The magnitude of the consequences will obviously be a function of the radioactive inventory of the waste repository at the time when the sequence starts. As this inventory decreases by natural decay, the consequences will also decrease and will eventually drop below the level of significance. 

In analyzing the safety of a waste repository, it is crucial to know the time period under consideration. A number of geologic processes and events are relevant for the safety analysis only if the time frame exceeds a certain range. As it is obvious that the hazard of a waste repository due to the decrease of its radioactive inventory will eventually approach a level that is no longer significant, it will be feasible to estimate a time frame for the safety analysis. This time frame will be called the significant period of the waste repository hazard. The estimation of... 

The initiated radioactive inventory for spent reactor fuel consists of actinides, fission products and activation products. As noted previously, (Gi. 21) the shorter lived fission products, such as Sr and Cs, and transuranic elements, such as Pu, Pu, are the main contributors to the radioactivity. However, performance assessments strongly indicate that the waste form matrix and the near field engineered barriers (e.g. clay backfill, etc.), can successfully retain and prevent any migration to the far field viromnent for one thousand years and probably much longer (> lO years). After the first thousand years the long lived nuclides such as Cs, Sn, Tc and Se among the fission products and the actinides Np, Pu, Pu, and Am become the major concern. 

The HLLW were successfully vitrified in two successive campaigns during the periods 1985-1986 and 1987-1991. The operation resulted in the production of 493 tons of glass product packaged in 1,503 canisters of 0.060 m- and 700 canisters of 0.150 m-. These canisters are in safe intermediate storage conditions at Belgoprocess until a geological disposal site is available around 2030. The total radioactivity inventory amounts to 4.44 Bq of beta emitters and 1.51 Bq of alpha emitters. 

Japan Company RANDEC is also committed to provide technical assistance, namely for evaluation of radioactive inventory and workers exposure, waste conditioning and project management. 

IAEA (1985 and 1999) Earthquake resistant design of nuclear facilities with limited radioactive inventory , TECDOC-348, IAEA, Vienna. 

The highest risk to workers results from direct radiation exposure, airborne release hazards, or radiological contamination in the work area. These hazards involve an irradiated target or the radioactive inventory of solidified process effluent and other target residue. 

For accidental releases, the HC3 radioactive material storage areas are administratively controlled to total radioactive inventories in each location to less than HC2 thresholds. Thus, by the definition of these thresholds in DOE-STD-1027-92, accidents in the radioactive material storage facilities would have the potential for only localized consequences. Also in accordance with the definition of the DOE-STD-1027-92 thresholds, accidental releases from the HCF have the potential only for significant on-site consequences. Thus, no release with the potential to cause significant environmental insult exists. 

Earthquake Resistant Design of Nuclear Facilities with Limited Radioactive Inventory... 

A nuclear reactor of this size contains an inventory of radioactive nuclides that can contaminate large areas - as demonstrated by the reactor accident of Chernobyl in April 1986. Therefore, at least in reactors in Western countries, a number of measures are taken to securely enclose the radioactive inventory. The fission products are surrounded by several barriers ... 

It Is recommended that further work be done by reactor engineers to determine whether such a shield Is feasible and to assess its effect on vessel size, radioactive inventory, permissible man access times following removal of the vessel Internals, and reactor operational characteristics. 

As a consequence of these nuclear reactions, the reactor of a nuclear power plant contains a very large radioactivity inventory consisting of radioisotopes of different chemical elements, from the lightest ones through the fission product... 

The small radioactive inventory typical of a small sized power reactor ... 

Based on these circumstances, JAPC has been executing the investigations and researches. Among these activities, Assessment of radioactive inventory and "Feasibility study of decommissioning method are described below. 

The WAGR hotbox is an interesting item with regard to its radioactive inventory. It sits above the top core reflector and neutron shield, and, as such, has received little neutron activation. It is, however, the first pennanent reactor component in which the coolant gas came into contact with after passing over the operating fuel pins. It is hence the first site for deposition of fission products which were from time to time released from failed fuel pins. 

Due to the fact that the design features, radioactive inventories and long-term behaviour of LWR fuel is completely different from those of HTR fuel further studies on the suitability of the CASTOR THTR/AVR cask to establish an adequate final disposal concept for HTR fuel have been currently initiated and will be carried out by Forschungszentrum Jiilich GmbH in cooperation with Gesellschaft fur Nuklear-Behalter mbH (GNB). 

A design basis shall be established for each experimental device associated directly or indirectly with the reactor. The radioactive inventory of the experimental device as well as the potential for the generation or release of energy shall be taken into consideration. A safety analysis shall also be performed, including an analysis of the damage that would be caused to the experimental devices by the postulated initiating events of the reactor. 

III-21. In a design analysis of the effects of a postulated fuel handling accident, such as the dropping of spent fuel during its transfer from the vessel to the storage pool, the first step is to determine the radioactive inventory of the fuel at the time of the accident. Assumptions about the details of the history of fuel irradiation need to be chosen so as to lead to conservative (i.e. high) estimates of the activity. 

TABLE 8.2. RADIOACTIVITY INVENTORY OF THE RAPSODIE REACTOR BEFORE DISMANTLING AS OF 1.1.1984 (VALUES AS OF 1.1.1994 IN PARENTHESIS). 

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