21. Jet pumps increase the flow of water through the reactor core . 22. This solution allowed for a very compact reactor core design. 23. Since nuclear fission creates radioactivity, the reactor core is surrounded by a protective shield. 24. In its central part, the reactor core 's heat is generated by controlled nuclear fission. 25. It consisted of an experimental reactor core installed in a modified S5W reactor plant. 26. The reactor core normally consists of 27 fuel elements, of about 30 kg of uranium. 27. About one-fifth of the reactor core had experienced inadequate cooling caused by uneven coolant flows. 28. The uranium-oxide fuel pellets would start to melt, releasing radioactivity into the graphite reactor core . 29. Therefore, one or more of the 200 reactor cores could conceivably sink, sooner or later. 30. While the submarine was only halfway through her design lifespan, her reactor core required refueling.
