The calculated distance (air line) between Yŏnggwang-ŭp and Chongjin is approximately 173 miles respectively 278 kilometers.
By car or train, the actual journey to Chongjin is certainly longer, as only the direct route (as the crow flies) between Yŏnggwang-ŭp and Chongjin has been calculated here.
Air line (approximately)
278 kilometers
150 nautical miles