The consideration of new nuclear power stations is split into two phases. The first phase addresses generic design matters (namely, acceptability of candidate nuclear power station designs) and the second deals with site-specific applications for permits under the Environmental Permitting Regulations 2010. Since a large nuclear power plant that utilizes a once-through cooling system may withdraw 800 million to 1 billion gallons of water a day, these plants are usually built next to rivers, lakes, or oceans. As the name implies, once-through cooling uses water per single time to cool and condense steam produced for electricity generation. Water produced from the condensed steam is reused in the generation process, but the water used for cooling is discharged back into the lake, river or ocean, with a temperature increase of up to 30 degrees . Condenser performance is also reduced by factors such as scale on the outside (steam side) of the tubes and by slime and scale (waterside fouling) inside. These effectively insulate the tube wall . The widely used Langelier Saturation Index is a useful indicator of carbonate scale formation but it is purely an equilibrium index and gives no indication of how much scale will form, or calcium carbonate will precipitate, in bringing the water to equilibrium. Scaling and corrosion are influenced by pH, hardness, alkalinity, total dissolved solids and temperature so in theory an equilibrium condition can be maintained so that neither occurs. Other problems like the water consumption caused by the evaporation losses of the towers are also the object of controversy at several sites (3). On the other hand using once-through cooling pass may solve some of these problems such as water consumption, which Egypt government is concerned with and the rejection of thermal discharges from cooling towers . Fouling risk is another environmental impact on nuclear power plant from using sea water as a cooling system, as it is classified as the deposition of marine biological organisms on certain surface called marine bio-fouling or classified as a deposition of chemical compounds such as calcium silicates and calcium carbonates, forming what is called chemical fouling; on the other hand fouling may also defined as (inorganic or organic) chemical formation . The bio-fouling species attached ranged from micro-organisms (bacteria, algae) to macro-organisms (mussels, barnacles, etc.) and particulate fouling. The possibility of fouling formation in seawater medium is increasing due to the increasing of TDS, Alkalinity, salinity and Ca-hardness concentrations, leading to formation of hard insulating layer inside the condensed tubes that cause a problem in heat transfer process in the selected cooling water system   .
2. Material and Methods
The coasts of Egypt extend over more than 3500 km along the Eastern Mediterranean and the Red Sea. The Mediterranean Alexandria coastal sector extends further eastward from Hammam to Abu Qir. This study aims to evaluate the environmental impacts resulted from selecting certain sites at the coastal line of Alexandria to see the acceptability of using one of these sites to be used as source of once-through pass cooling system in a pressurized water reactor (PWR) with avoiding any environmental impacts on the suggested cooling water type,field study has been done to select the suggested sites (Abou-Qir, Sidi Kirr, Al Mex, Estern Harbour and Sidi Abd Elrahman), the Abou-Qir geographic coordinates are 31˚18'22.0''N 30˚09'52.0''E, while in Sidi Kirr are 31˚05'21.0''N 29˚35'29.0''E, and Al Mex coordinates with latitude 50.498830 and with longitude 3.611640. on the other hand, the Estern Harbour coordinates arelies between 29˚52'57''E - 29˚54'27''E and 31˚12'00''N - 31˚12'54''N, and Sidi Abd Elrahaman coordinates are 30˚57'59.99"N 28˚43'59.99"E. The Physic-chemical analysis of sea water parameters had been measured (temperature, pH,
Table 1. Interpretation of Langlier saturation index (6).
Table 2. Interpretation of Ryznar stability index (6).
3. Results and Discussions
Figure 1 showed that Al has the highest value of Langlier Saturation Index (LSI) in Estern harbor 1.78 while the lowest LSI value at Sidi Abd Elrhaman region with 1.12. On the other hand Figure 2 shows the highest value of Ryznar Stability Index (RSI) was found at Sidi Abd Elrhaman with 5.86 while the lowest RSI values found in Estern Harbor with 5.04, so depending on Langlier stability index or Ryznar stability index the selected sites for suggesting cooling system are with low tendency for scale formation . Table 3 showed that the calculated LSI values for selected regions are respectively (1.43, 1.58, 131, 1.78 and 1.12) and the calculated RS values are respectively (5.04, 5.24, 5.48, 5.04 and 5.86) all these values indicate that there low tendency for scale formation and possibility of corrosion at these selected areas as showed at Table 1 (0.5 - 2), On the other hand Table 2 showed that the degree of scale formation which is light scale (5 - 6) . Table 4 showed also that There is ahighly significant t-test +ve correlations (P < 0.01) between Ca-hardness and LSI value which is (+0.127) on the other hand Table 5 showed that there is There are highly significant t-test highly significance t-test +ve correlations (P < 0.01) between Ca-hardness and RSI value (+0.333) as both LSI and RSI stability indexes have its basis in the concept of saturation level to quantify the relationship between calcium carbonate saturation state and scale formation. All these previous results may support the using of once-through cooling system at those selected sites (Abou-Qir, Sidi Kirr, Al Mex, Estern Harbour and Sidi Abd Elrhaman) as a source of nuclear power plant cooling water besides the using of anticorrosion chemicals in these selected sites
Figure 1. Determintion of Langerlier saturation index (LSI) in different sites in Alexandria costal line.
Figure 2. Determintion of Ryznar stability index (RSI) in different sites in Alexanderia coastal line.
Table 3. The mean average values of physicochemical parameters analysis of the selected areas during the period 2/1/1015 to 3/6/2015.
*pH is not a average value.
Table 4. Correlation coefficient (r+) between LSI and Ca-hardness values of the selected areas during the period 2/1/1015 to 3/6/2015.
T-test for significance of r+, P < 0.001.
Table 5. Correlation coefficient (r+) between RSI and Ca-hardness values of the selected areas during the period 2/1/1015 to 3/6/2015.
T-test for significance of r+; P < 0.001.
of cooling water with using nickel copper alloys in condenser material to prevent any attack of corrosion and at selected sites. On the other hand there are another protection methods in case of using once-through cooling system in once-through cooling power plants, such as Abou-Qir and Sidi Kerir steam power stations, like screens and debris filters with different diameters to prevent any debris and fouling accumulation beside the low degree of scale formation which may lead to the decreasing the efficiency of cooling that leads to negative impacts to nuclear power plants operation
− Using the once-through pass cooling system is a suitable cooling system of a suggested nuclear power for different selected coastal regions, of Alexandria coast (Abu-Qir, Sidi Kerrir, Estern Harbour, El Max and Sidi Abd Elrhaman) due to the decreases of its possibility of exposure to corrosion and scale formation impacts.
− The importance of using different corrosion and scale formation indexes (Langelier saturation index and Ryznar stability index) when suggesting a new cooling system of nuclear power plant especially when it is located at coastal area to avoid any environmental impacts may occur on the suggested cooling system.
− Using nickel-copper alloys in condenser prevents any possibility of attack of corrosion besides using pretreatment methods of cooling water (screens and debris filter) case of using once-through cooling system such as other coastal conventional steam power of Alexandria.
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