Chemical and Biological Engineering ETDs

Publication Date

9-9-2015

Abstract

Calcium leached from NUKON fiberglass in containment following a Loss of Coolant Accident (LOCA) could lead to the formation of chemical precipitates that in turn cause head-loss increase due to filtering through a fibrous debris accumulation at the sump pump screens. Experiments conducted on the bench scale show that the level of fiberglass destruction does not affect the concentration of calcium leached. Reduced-scale experiments were conducted on three solution inventory scales (0.5 L, 31.5 L, 1136 L) with three different flow conditions, and two fiberglass concentrations to investigate calcium release from NUKON fiber. Results showed that the calcium leached at a constant temperature of 80 C in borated-buffered solution over a 30-day period has a repeatable behavior. The calcium concentration behavior can be divided into four distinct regions as a function of time. These distinct regions are comprised of a prompt release of calcium, a metastable region, followed by an autocatalytic drop region, and a final stable concentration region. The prompt release of calcium determined by the fiberglass concentration determined the maximum calcium concentration reached and the time taken to reach the metastable position. The metastable position of calcium is due to the formation of an amorphous calcium phosphate (ACP) whose solubility is decreased by the presence of magnesium, which also leaches from NUKON fiberglass. Magnesium has been shown to behave in a similar manner as calcium. The magnesium concentration initially increased to the metastable solubility limit of calcium and then droped out of solution. This drop in magnesium concentration coincides with the autocatalytic drop in calcium concentration to the final stable position. Understanding the calcium leaching from NUKON fiberglass, a prototypic debris bed prepared with NUKON fiberglass and particulates was generated in a vertical head-loss column to quantify the corresponding head-loss change due to the in situ calcium leaching. The measured head-loss slope was compared to regional changes in calcium concentration and found to continually increase from 4.4 H2O to 12.2' H2O (head-loss temperature corrected to 20oC over an experimental period of 20 days.'

Keywords

GSI-191, LOCA, NUKON fiberglass, Calcium, leaching, Trisodium phosphate (TSP), calcium, precipitation; Calcium phosphate., Calcium magnesium phosphate., Nuclear reactors--Containment., Water cooled reactors--Loss of coolant., Water cooled reactors--Deterioration.

Sponsors

Southern Nuclear Operating Company

Document Type

Thesis

Language

English

Degree Name

Chemical Engineering

Level of Degree

Masters

Department Name

Chemical and Biological Engineering

First Committee Member (Chair)

Howe, Kerry

Second Committee Member

Han, Sang M.

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