By Jan Strupczewski BRUSSELS (Reuters) – European Union leaders will declare the start of accession talks with Ukraine at their summit in Brussels, their chairman Charles Michel said on Thursday in a surprise announcement. The talks themselves are likely to take years. Ukraine, which has a population of 44 million and is geographically bigger than any EU member, presents some unique challenges for admission to the 27-member bloc: MONEY Ukraine’s per capita GDP is less than a third of the EU average in terms of purchasing power, which means that it would immediately become a net recipient of fu…