Test of dissolution of simulated corrosion-oxides in primary loop of the AP1000 reactor
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Test of dissolution of simulated corrosion‑oxides in primary loop of the AP1000 reactor Yu‑jie Cui1 · Ming‑liang Wu1 · Wei Zhao1 · Yong‑xian Wang1 · Li‑xiao Guo1 · An‑xi Cui1 Received: 6 June 2020 / Accepted: 22 September 2020 / Published online: 10 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The AP1000 reactor of China would overhaul for the first time. In order to achieve in-service decontamination of AP1000 primary loop equipment, three simulated corrosion oxides of the AP1000 reactor primary loop were prepared by sedimentation-calcination method, and ultrasonic chemical dissolution test was conducted. The analysis of the characteristics of the simulated oxide showed that the addition of zinc resulted in a different composition of the oxides from that of ordinary PWR, and that is smaller particle size and tighter bonding. Suitable decontaminants and decontamination processes were identified by the dissolution laws of the simulated oxides in the experiment. Keywords AP1000 · Zinc addition · Sedimentation-calcination · Simulated oxide · Dissolve
Introduction In the early 1980s, General Electric found that Boiling Water Reactor using condensate tubes with brass piping had significantly lower radiation fields in the piping outside the stack core than Boiling Water Reactor using stainless steel condensate tubes, and tested the heat-carrying agent for zinc ion concentrations of 5–15 ppb [1, 2]. The analysis is that the zinc in the brass pipe is corroded, which enters the loop and prevents the formation of 60Co. In 1994, the Farley Nuclear Power Station in the United States became the world’s first Pressurized Water Reactor nuclear power plant to add zinc in primary loop at a concentration of 40 ppb,which resulted in a 24% reduction in radiation dose during the first outage overhaul compared to the previous cycle [3, 4]. In Germany, zinc was added in the primary loop of the PWR and the radiation dose rate was significantly reduced [5, 6]. The high-temperature and high-pressure environment of the reactor results in a double-layer structure of the oxide film formed on the internal material surface [7]. The inner oxide film is more dense and less porous compared to the outer layer, and when zinc ions are added to the coolant, the zinc ions first enter the outer structure of the oxide and then enter the inner oxide * Yu‑jie Cui [email protected] 1
Department of Waste Management, China Institute for Radiation Protection, Xuefu 102, Taiyuan 030006, China
film under the effect of thermodynamics, and because Z n2+ 2+ 2+ has a higher tetrahedral selection energy than Co , Fe and Ni2+ [8, 9], thus displacing radioactive elements such as cobalt–nickel, and after the inner layer is saturated, the zinc ions in the coolant form a dynamic equilibrium with the outer oxide film of the metal. For austenitic stainless steel, the oxide film after addition of zinc is ( ZnnFe1−n)Cr2O4 [10], which is significantly different from the corrosive oxides of the ordinary pressurized water pile primary loop. The Sa
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