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Solid Radioactive Waste Strategy Report.pdf - UK EPR

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<strong>EPR</strong> <strong>UK</strong><br />

N° NESH-G/2008/en/0123<br />

REV. A PAGE 239 / 257<br />

e) Storage wells internal atmosphere checking<br />

Periodic monitoring of the primary and secondary barrier integrity is undertaken by analysing<br />

the internal well atmosphere. If a leak is detected from one of the storage canisters, both<br />

canisters are retrieved from the well, transferred to the unloading cell and opened. The fuel<br />

assemblies are placed into two new canisters docked in the transfer tunnel. Once emptied,<br />

the failed canisters are dismantled, placed into a specific canister and stored in a dedicated<br />

well. The new canisters are processed in the normal way and returned to the vault.<br />

Note: if canisters are known to hold leaking fuel, they are subject to more frequent<br />

controls in the storage well.<br />

f) Storage of fuel assemblies canisters<br />

Each dry storage facility module consists of two storage vaults. The dry storage vault<br />

modules are constructed as separate units with separate ventilation systems. This modular<br />

approach makes the design flexible and allows the facility to respond to a need for increased<br />

storage capacity.<br />

Each vault includes a number of wells to accommodate the fuel assembly canisters. The<br />

canisters are stored vertically, stacked on 2 levels, inside the air-cooled storage wells.<br />

g) Canisters retrieval<br />

At the end of the storage period, canisters will be retrieved and transferred into the dedicated<br />

unloading cell before being exported for final disposal or another long-term storage facility.<br />

Cooling of storage vaults<br />

Each storage module (comprising 2 vaults) is equipped with an independent cooling circuit.<br />

The air cooling system is based on natural convection through a jacket around each vertical<br />

storage well and up a stack. Fresh air is supplied through air inlets into the vault bottom<br />

plenum. An intermediate plate is located inside each vault to ensure the separation between<br />

the low inlet plenum and the vault internal volume. Cooling air is circulated in the well tube<br />

annulus and warm air is removed through the module upper plenum before being exhausted<br />

through the stack.<br />

All discharges will be continuously monitored. The cooling system is designed to maintain<br />

concrete walls and stored package temperatures below the maximum permissible values.

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