Japan's naphtha imports for ethylene production in April rose 4.5% month on month to 1.247 mln tons, a s per the Ministry of Economy, Trade and Industry. As per Platts, imports rose as the impact of the March 11 earthquake and tsunami waned. But, compared with April 2010, imports were down 8.5%. Japan's naphtha import prices in the month rose 6.7% from March to $945.30/mt, up 28.8% from a year earlier. Several naphtha-fed steam crackers were shut after the quake and tsunami. Mitsubishi Chemical plans to keep its two naphtha-fed steam crackers at Kashima in eastern Japan shut until at least late May for repairs. The No. 1 cracker has capacity to produce 375,000 tpa of ethylene and the No. 2 cracker 476,000 tpa. JX Nippon Oil and Energy's Kawasaki steam cracker with capacity to produce 404,000 tpa of ethylene was shut March 11-27. Maruzen Petrochemical's Chiba steam cracker, with a production capacity of 550,000 tpa of ethylene, was shut after the quake and restarted on April 4.