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Radioactive waste clipt12/29/2023 ![]() A loaded, concrete cask may contain ∼10 tons of SNF with a decay heat of ∼20 kW, is ∼6 m high, has a diameter of ∼3.4 m, has a concrete-wall thickness of ∼0.8 m, and weighs ∼170 tons.įIGURE 2. There can be significant decay heat thus, air vents allow ambient air to flow into the annular zone between the canister and cask, to flow up the annular zone, and to exit near the top of the cask. The canister is then placed in a steel-lined, concrete cask, which provides radiation shielding and physical protection of the SNF against severe events (tornados, accidents, etc.). Consequently, the canister contains an egg-crate type structure to hold the multiple SNF assemblies vertically within the canister. Typical SNF assemblies are ∼4 m long with a square cross section that is typically 10 to 25 cm on a side. The SNF is placed in a stainless steel canister, which is then filled with helium, and welded shut. A typical concrete storage cask is shown in Fig. These are typically (1) air-cooled, shielded concrete vaults or (2) above-ground concrete or steel casks. ![]() Typically, the minimum storage times are 2 to 5 years.Īfter some period of time, the SNF is transferred to dry storage systems. The water provides radiation shielding to protect the workers from gamma radiation and cools the SNF. SNF is so radioactive and generates so much heat immediately after discharge that, in most cases, it is stored under water in pools at the reactor site. This storage reduces transport and disposal costs and risks. It is universal practice to store SNF for some period of time before transport and disposal to allow the radioactivity and decay heat to decrease ( Table I). One of the most radioactive wastes is SNF from power reactors. For other radioactive materials, a period of storage reduces the radioactivity and heat generation and, in turn, reduces transport and disposal site costs and risks. ![]() Such storage reduces the radioactivity by about a factor of 1000. The general rule-of-thumb is that a waste stored for 10 times the half-life of the primary radionuclide is no longer a radioactive waste. Radioactive wastes are stored to (1) allow some radioactive wastes to decay to nonradioactive wastes, (2) reduce transport risks (3) provide lag storage between waste generator, treatment, and disposal sites (4) simplify disposal and (5) manage radioactive wastes until disposal facilities become available.įor radioactive wastes containing only radionuclides with half-lives measured in days or weeks, such as some medical and research isotopes, storage for weeks or months eliminates the radioactivity and converts the radioactive waste into a nonradioactive waste. Forsberg, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 III.B Storage
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