Test rig of straight tube type sodium-heated steam generator

The steam generator takes an important position specifically in the development of sodium-cooled fast breeder reactors. Though the electrically heated test rig of 0.1 MW for steam generators was already produced and tested, the new 0.1 MW sodium-heated test rig for straight tube type steam generators has been manufactured to forward the development of straight tube steam generators strongly. The testing purpose of the rig is to grasp the characteristics in the departure from nucleate boiling phenomenon caused on the water/vapor side under sodium-heating condition. At present, the static characteristic is being tested among the following planned tests: (1) static test (departure from nucleate boiling test, heat transfer test), (2) dynamic characteristic test, (3) flow stability test, (4) water leak detector test, (5) endurance test of sodium-immersed rupture disc, (6) thermal shock test of tube plates. The rig is composed of water and sodium systems of closed loops, and the straight tube type steam generator. Each part of the rig (steam generator, water system, sodium system, control system, alarm, interlock, cover gas) is equippped with a variety of detectors. From the results of trial run and static characteristic test, the time required to reach 100% load from start-up is about 15 hours, and 8 hours are required from 100% load to shut down. An example of the static characteristic showed that the gradient of sodium temperature distribution changed remarkably at the part 6.6 m downward from the sodium inlet. This shows that the departure from nucleate boiling occurred at the place. Calculation supported the above estimation. (Wakatsuki, Y.)