Pond storage

Stradling GN, Stather JW, Gray SA, et al. 1989. Assessment of intake of an actinide-bearing dust formed from the pond storage of spent magnox fuel. Radiat Prot Dosim 26(l/4) 201-206. 

The site currently contains very large inventories of radioactive waste. This is principally present as spent fuel, in the dry storage units (Tanks 2A, 2B and 3 A, Figmes 1 and 2). The potential inventory in the three dry storage units is of the order of lO Bq. Another very contaminated facility is Building 5, the former pond storage facility for spent fuel. 

In Section 2.5, we discussed the production of energy by nuclear fission, and the reprocessing of nuclear fuels. We described how short-lived radioactive products decay during pond storage, and how uranium is converted into [U02][N03]2 and, finally, UFg. One of the complicating factors in this process is that the fuel to be reprocessed contains plutonium and fission products in addition to uranium. Two dilferent solvent extraction processes are needed to elfect separation. 

Eventually, the fuel in a nuclear reactor becomes spent, and, rather than being disposed of, it is reprocessed. This both recovers uranium and separates from the fission products. Short-lived radioactive products are initially allowed to decay while the spent fuel is retained in pond storage. After this period, the uranium is converted into the soluble salt [U02][N03)2 (see Box 7.3). In the series of reactions 3.18 3.21, the nitrate is converted into UF. ... 

Transport and storage of LWR irradiated fuel have been carried out safely using a variety of transport flasks and holding inserts. In particular, the Excellox Flask utilized for PWR fuel transport with an insert also utilized for pond storage, originally designed for 7 fuel elements. 

Eventually, the 92 U fuel is spent, and requires reprocessing. This recovers uranium and also separates from the fission products. First, the spent fuel is kept in pond storage to allow short-lived radioactive products to decay. The uranium is then converted into the soluble salt [U02][N03]2 and finally into UFs ... 

The nuclear fuel industry uses large quantities of F2 in the production of UFg for fuel enrichment processes and this is the major use of F2. Reprocessing of spent nuclear fuels involves both recovery of uranium and separation of from fission products. Short-lived radionuclides decay during a period of fuel storage (pond storage). After this, uranium is converted in the soluble salt [U02][N03]2, and then into UFs (see Box 7.3). 

Most carbide acetylene processes are wet processes from which hydrated lime, Ca(OH)2, is a by-product. The hydrated lime slurry is allowed to settle in a pond or tank after which the supernatant lime-water can be decanted and reused in the generator. Federal, state, and local legislation restrict the methods of storage and disposal of carbide lime hydrate and it has become increasingly important to find consumers for the by-product. The thickened hydrated lime is marketed for industrial wastewater treatment, neutrali2ation of spent pickling acids, as a soil conditioner in road constmction, and in the production of sand-lime bricks. 

Eliminate use of open ponds - Open ponds used to cool, settle out solids and store process water can be a significant source of VOC emissions. Wastewater from coke cooling and coke VOC removal is occasionally cooled in open ponds where VOCs easily escape to the atmosphere. In many cases, open ponds can be replaced with closed storage tanks. 

Where potential flooding to the site is minimal an alternative to the balance pond could be an open-trench system that could provide on-site storage and added security to watercourses. 

Similar convection processes occur in liquids, though at a slower rate according to the viscosity of the liquid. However, it cannot be assumed that convection in a liquid results in the colder component sinking and the warmer one rising. It depends on the liquid and the temperatures concerned. Water achieves its greatest density at approximately 4°C. Hence in a column of water, initially at 4°C, any part to which heat is applied will rise to the top. Alternatively, if any part is cooled below 4°C it, too, will rise to the top and the relatively warmer water will sink to the bottom. The top of a pond or water in a storage vessel always freezes first. 

It is required to pump cooling water from a storage pond to a condenser in a process plant situated 10 m above the level of the pond. 200 m of 74.2 mm i.d. pipe is available and the pump has the characteristics given below. The head lost in the condenser is equivalent to 16 velocity heads based on the flow in the 74.2 mm pipe. 

Devise a control system for the distillation column described in Chapter 11, Example 11.2. The flow to the column comes from a storage tank. The product, acetone, is sent to storage and the waste to an effluent pond. It is essential that the specifications on product and waste quality are met. 

In seasonal snow/ice storages frozen water is stored from winter to summer, when the cold is utilized. The snow/ice can be stored indoor, on ground, in open ponds/pits and under ground, Figure 200. 

Figure 201. Natural snow melt in open pond snow storage...

A number of different open pond snow and ice storage techniques have been suggested. In Ottawa a storage for 90,000 m3 of snow in an abandoned rock quarry (120 x 80 x 9.5 m3, L x W x H), was studied. The mean cooling load was 7,000 kW. A light colored PE plastic tarpaulin was suggested as insulation, with melt water re-circulation for cold extraction. The estimated payback time was 10 years (Morofsky, 1981). 

The snow storage was built in 1998/1999. It is a shallow watertight pond (130-64 m) with slightly sloping (about 1%) asphalt surface, Figure 203. The... 

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