Decontamination of corrosion oxides in the heat transport system of a pressurized heavy water reactor using chelate-free inorganic acid

Figures & data

Table 1. Chemical compositions and pHs of the initial HyBRID process solution and spent process solution

Condition		Initial HyBRID process solution [11]	Spent process solution
Composition (ppm)	N2H4	1,600	1,000
	SO4^−	2,600	2,600
	Cu^2+	31.8	31.8
	Fe^2+	0	350
pH		2.75	2.60

Figure 1. The changes in (a) concentration of dissolved Fe ions; (b) dissolution rate of magnetite; (c) pH; (d) concentration of chemical species of hydrazine during dissolution in the existing HyBRID process solution.

Figure 2. Results of equilibrium calculations on the precipitation step in the recycling process using Ba(OH)_2.

Table 2. Concentrations of metal ions and pH in the purified process solution after the precipitation and filtration steps

Molar ratio (Ba(OH)2 / SO4^2-)	[Fe ion] (ppm)	[Cu ion] (ppm)	[SO4^2- ion] (ppm)	[N2H4] (ppm)	pH
0.40	2.517	0.191	1,560	1,010	8.02
0.45	1.843	0.282	1,460	1,000	8.17
0.50	0.714	0.322	1,310	1,020	8.27
0.55	0.536	0.219	1,180	1,000	8.36
0.60	0.332	0.150	1,020	1,030	8.63
0.70	0.150	0.046	790	1,010	9.31

Figure 3. Changes in the colors of the solutions during the recycling with changes in the molar ratio of Ba(OH)₂/SO₄²⁻.

Table 3. Injection amount of decontamination reagents for reducing the purified to the initial condition

Mole ratio (Ba(OH)2 / SO4^2-)	Concentration of additional composition
	N2H4 (ppm)	SO4^2- (ppm)	Cu^2+ (ppm)
0.55	600	1,420	31.8
0.60	600	1,580	31.8
0.70	600	1,810	31.8

Figure 4. Process flow diagram of the PHWR decontamination using the recycled HyBRID solution.

Figure 5. Comparison of Fe ion concentration after dissolution of Fe₃O₄ using initial HyBRID process solution and the recycled process solution.

Figure 6. Scheme of the decontamination process of the heat transfer system in the PHWR including recycling process and pH monitoring method.

Figure 7. Result of simulated magnetite dissolution test using HyBRID decontamination process for PHWR and monitoring method.

Wangkyu C, Huijun W, Chonghun J, et al. Development of decommissioning, decontamination, and remediation technology for nuclear facilities: develo pment of advanced decontamination technology for nuclear facilities. Deajeon (Republic of Korea): Korea Atomic Energy Rese arch Institute; 2017. (KAERI/RR-4230/2016).

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