Editing Pressurized water reactor (section)

=== Fuel ===
{{Main|Nuclear fuel}}

[[File:Nuclear fuel element.jpg|thumb|'''PWR fuel bundle''' This fuel bundle is from a pressurized water reactor of the nuclear passenger and cargo ship [[NS Savannah|NS ''Savannah'']]. Designed and built by [[Babcock & Wilcox]].]]

After enrichment, the [[uranium dioxide]] ({{chem|UO|2}}) powder is fired in a high-temperature, [[sintering]] furnace to create hard, ceramic pellets of enriched uranium dioxide. The cylindrical pellets are then clad in a corrosion-resistant zirconium metal alloy [[Zircaloy]] which are backfilled with helium to aid heat conduction and detect leakages. [[Zircaloy]] is chosen because of its mechanical properties and its low absorption cross section.<ref>{{cite web|url=http://www.fusion.org.uk/techdocs/icfrm9_fortkard.pdf |title=Uses of Zirconium Alloys in Fusion Applications |last=Forty |first=C.B.A. |author2=P.J. Karditsas |publisher=EURATOM/UKAEA Fusion Association, Culham Science Center |access-date=2008-05-21 |url-status=dead |archive-url=https://web.archive.org/web/20090225155448/http://www.fusion.org.uk/techdocs/icfrm9_fortkard.pdf |archive-date=February 25, 2009 }}</ref> The finished fuel rods are grouped in fuel assemblies, called fuel bundles, that are then used to build the core of the reactor. A typical PWR has fuel assemblies of 200 to 300 rods each, and a large reactor would have about 150–250 such assemblies with 80–100 tons of uranium in all. Generally, the fuel bundles consist of fuel rods bundled 14&nbsp;×&nbsp;14 to 17&nbsp;×&nbsp;17. A PWR produces on the order of 900 to 1,600&nbsp;MW<sub>e</sub>. PWR fuel bundles are about 4&nbsp;meters in length.<ref>{{harvnb|Glasstone|Sesonske|1994|p=21}}</ref>

Refuelings for most commercial PWRs is on an 18–24 month cycle. Approximately one third of the core is replaced each refueling, though some more modern refueling schemes may reduce refuel time to a few days and allow refueling to occur on a shorter periodicity.<ref>{{harvnb|Duderstadt|Hamilton|1976|p=598}}</ref>