researchers at johns hopkins university examined photos of a lightwater reactor under construction in yongbyon. they compared the one on the left taken in march with the one on the right taken in april. the researchers say the cylindrical parts of the containment building appears to be higher in the new image. and they say work on a roof adjacent to that area has been completed. north korean officials claim the plant will be used to produce electricity. >>> with tensions rising over north korea's activities, the united states and south korea are working together to keep their militaries ready. air force personnel from the two countries are staging their largest ever joint drill on the korean peninsula. about 50 fighter jet bess longing to both countries are taking part in exercises nicknamed max thunder. the drills began on may the 7th and continue through friday. the allies' air forces holds regular drills twice a year to prepare for the possible aift confrontation with north korea or attacks on the south's military bases. during one exercise, f-15 and f-16 jet fighters took off from south ko