50μm Optical bright field and dark-field metallographic images of a Zircaloy- 4 cladding oxidised in air at 850C(see text section D for signification of regions 1,2,3 and 4) from Nuclear Engineering and Design,Volume 239,Issue 2,February 2009,Pages 244-253 99 Optical bright field and dark-field metallographic images of a Zircaloy- 4 cladding oxidised in air at 850 oC (see text section D for signification of regions 1, 2, 3 and 4) from Nuclear Engineering and Design, Volume 239, Issue 2, February 2009, Pages 244–253