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XYLENE POWER LTD.

FAST NEUTRON REACTOR (FNR) SITING

By Charles Rhodes, P.Eng., Ph.D.

INTRODUCTION:
Elsewhere on this website Fast Neutron Reactors (FNRs) have been identified as the primary source of energy for meeting mankind's future energy needs. This web page focuses on FNR siting criteria.
 

FNR SITING CRITERIA:
A CANDU reactor is generally sited at the edge a large body of water to allow heat dissipation by direct water cooling. On the other hand a liquid sodium cooled Fast Neutron power Reactor (FNR) should be sited sufficiently above nearby water bodies to ensure that even under worst case earthquake/tsunami/flood and sea level rise conditions there will never be any contact between the primary sodium and water.

Since a FNR should not be sited close to the elevation of a major water body the FNR must dissipate heat via evaporation of water in cooling towers. Hence, a FNR must be located sufficiently close to a secure supply of water to allow economic cooling tower operation and sufficiently far from urban centers to make use of cooling towers acceptable to the public. Almost no one chooses to reside adjacent to a 400 foot (122 m) high natural draft cooling tower. Hence the cooliing towers for a FNR need significant dedicated land area.

In places with adjacent steep granite mountains a cooling tower can be concealed within a granite core mountain. This cooling tower concealment methodology might be applied in mountainous regions of British Columbia or Labrador but it is impractical in most of Ontario.

For both safety and long term structural stability the sodium pool of an FNR should be installed in a cavity cut out of bedrock.

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. The shale that typically exists about 7 m below grade under Toronto has a maximum load bearing capacity of about 5000 kPa. Shale is not as good as granite but it is sufficient for FNR support.

FNRs must be protected from ground water and from malevolent attacks from above. To prevent a malevolent attack from above from causing serious consequences the primary liquid sodium pool surface must be sufficiently below grade level to contain the liquid sodium, independent of the pool walls. Then it is essential to remove heat from the liquid sodium to reduce its temperature to under 200 degrees C, to cover the sodium pool to exclude rain water, and to flood the sodium surface with argon cover gas to prevent further sodium oxidation. A spare temporary sheet metal roof should be stored on site and should be available for immediate deployment to exclude oxygen and rain water in the event of a major FNR roof failure.

To ensure that there is no water triggered below grade liquid sodium tank failure and to ensure containment of the liquid sodium after an earthquake that is sufficiently violent to rupture the three primary liquid sodium containment walls the surrounding ground should be impervious and should be dry down to at least 30 m below grade level. Thus ideally the FNR should be located within a broad rock hill that rises at least 30 m above its immediate surroundings. The top surface of the hill must be paved or otherwise sealed to cause rain water to run off the sides of the hill instead of penetrating the hill.

The hill should be broad enough to protect the FNR liquid sodium tanks from a malevolent direct impact by a large aircraft travelling at close to the speed of sound.
 

PILOT FNR:
A pilot FNR is required for technology development, main FNR startup assistance and personnel training purposes. It is contemplated that a pilot FNR would have 24 core bundles and 28 blanket bundles. The fuel tube assembly would be:
8 X 0.4 m = 3.2 m wide
resulting in an inside primary sodium pool width of:
3.2 m + 2.8 m + 2.8 m = 8.8 m

The corresponding inside pool length would be:
8.8 m + 3.5 m + 3.5 m = 15.8 m

The pilot reactor primary sodium volume would be:
16 m X 15.8 m X 8.8 m = 2225 m^3

The pilot reactor would have a themal output of about 48 MWt. This themal output would assist in startup of the main reactor by performing functions such as initial sodium melting to permit fuel bundle installation.
 

SODIUM HANDLING:
There should be an adjacent spare liquid sodium tank of sufficient capacity to hold all the primary liquid sodium so as to permit major maintenance/repairs to the FNR primary liquid sodium tank. There must be a means of easily and rapidly transferring heat emitting fuel bundles from the main liquid sodium tank to the spare liquid sodium tank and vice versa.

The sodium will likely be delivered to the site as a solid in open top 55 US gallon steel drums with removeable covers. There may be as many as 40,000 such drums. These drums need to be stored on pallets in groups separated by aisles that act as fire breaks and provide access for fire suppression. A safe drum pallet size is 30 inches X 30 inches. Hence exclusive of aisles the space requirement is:
(30 inches X 30 inches) / drum X 9225 m^3 X 5 drums / m^3 X (.0254 m / inch)^2 = 26,782 m^2

Allowing for aisle area equal to 3 X storage area implies a requirement for 107,128 m^2 = 0.11 km^2 for sodium drum storage.

The drums will likely arrive by rail. Hence the site will need additional area for a rail siding and cargo transfer of:
1 Km X 50 m = .050 Km^2

The FNR needs to have multiple adjacent cooling towers, to provide a secure heat sink. There must be an extremely secure source of water to feed the cooling towers. Hence the hill containing the FNR should be located near a major river, lake or the ocean.

The drainage required to ensure dryness of the hill will likely have an adverse effect on nearby water wells. The combination of the hill and the cooling towers will be more prominent on the horizon than a cluster of wind turbines of similar height. To avoid problems with neighbours it is recommended that the utility that owns the FNR should purchase all the land within a 1 km radius of the FNR. Hence from a simple land acquisition perspective it makes sense to locate several FNRs in a cluster to minimize land acquisition costs. To put this issue in perspective, if the average land area per FNR is 1 km^2 and the cost of land is $50,000 per hectare the minimum cost of the land per FNR is about:
1 km^2 X 100 hectares / km^2 X $50,000 / hectare = $5,000,000
 

POWER TRANSMISSION CORRIDOR:
Also important is the cost of an electricity transmission corridor from the FNR to the electricity load.
 

URBAN LOCATION ISSUES:
Near a major metropolis this land acquisition cost could easily increase 20 fold.

Also important is the proximity to a metropolis where the highly trained personnel required to assemble, operate and maintain thr FNR can comfortably live. These real estate considerations point to the wisdom of Ontario Hydro in establishing during the 1970s major thermal electricity generation sites at Bruce, Darlington, Nanticoke and Pickering and in laying out major electricity transmission corridors in Ontario. Today the whole issue of nuclear reactor siting and long term electricity transmission corridor planning needs to be revisited.
 

FNR SITE AND TRANSMISSION CORRIDOR RESERVATION:
Displacing fossil fuels will require about a seven fold increase in nuclear power generation and transmission capacity in Ontario. Hence the government of Ontario should identify and prohibit new development on land that will be required for nuclear power stations and their related energy transmission and highway corridors.
 

This web page last updated October 30, 2016.

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