Mass transfer of corrosion products in high temperature, high pressure water circuits, part 2 - preliminary experiments

Evans, JV; Nicholson, FD

Mass transfer of corrosion products in high temperature, high pressure water circuits, part 2 - preliminary experiments

Files

AAEC-E-376.pdf(1.24 MB)

Date

1976-07

Authors

Evans, JV

Nicholson, FD

Publisher

Australian Atomic Energy Commission

Abstract

The behaviour of iron oxide crud was studied at 25ºC and over the range 240 to 270ºC in a high pressure water loop. Crud deposition and removal was measured in two parallel, heated Zircaloy-2 tubes using iron-59 as a radioactive tracer. This proved to be a powerful technique capable of detecting crud deposits less than 3 run thick. Rapid deposition of crud was observed following injection into the loop of an iron oxide suspension or a ferric nitrate solution. Crud deposited preferentially on heated surfaces when they were present but not to the exclusion of deposition elsewhere; hot spots on heated surfaces attracted additional deposits. Subcooled boiling appeared to be a more important factor than bulk boiling in the enhancement of crud deposition. The initial rapid deposition of the bulk of the crud throughout the loop was usually followed by a slower transfer of crud from other surfaces to any heated surface present. Unsteady operating conditions, e.g. a change in power, temperature or pH, frequently caused crud bursts, but once steady conditions were re-established the entrained crud was quickly redeposited. The bulk of deposited crud was not readily re-entrained, particularly from heated surfaces, so that crud bursts involved only a fraction of the total crud deposited. Ferric nitrate solutions injected into the loop formed haematite which deposited more slowly and formed more mobile deposits than magnetite which was injected directly into the loop as a slurry. Examination of deposits from both sources showed them to be even and tightly adherent, being removed only with difficulty.

Keywords

Primary coolant circuits, Subcooled boiling, Mass transfer, pH value, Deposition

Citation

Evans, J. V., & Nicholson, F. D. (1976). Mass transfer of corrosion products in high temperature, high pressure water circuits part 2, preliminary experiments (AAEC/E376). Lucas Heights, N.S.W.: Australian Atomic Energy Commission Research Establishment.