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Experimental Study and Optimization of Nuclear Grade Boric Acid Production Process

Ahmadian Koudakan, Payam | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49416 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Outokesh, Mohammad; Aflaki Pashaki, Fereydoon
  7. Abstract:
  8. Boric acid (H3BO3) is a weak monobasic acid that exist as a white powder in the standard conditions. In industry, it is used in manufacturing of fiberglas filaments, precious metals soldering and production of flat panel LCD displays. In all of these applications, normal grade boric acid is used, but nuclear industry demands an ultrapure boric acid (UPA) for controlling of the reactivity and power levels in pressurized water reactors. Annual consumption of UPA in Bushehr Power Plant (BPP) is around 60 metric tons. Currently, this amount is imported from Russia, but atomic energy organization of Iran plans to displace it by the acid made inside the country. Domestic production of UPA in addition to covering the need of the BPP, can generate a surplus for the national pharmaceutical industries. The present study can be considered as the first phase of the atomic energy’s mother project, and it was aimed at preparation of UPA from the commercially available boric acid. Our method of purification was a combination of cation exchange (CX), anion exchange (AX) and recrystallization (RC). Solubility of boric acid increases with temperature dramatically, and it precipitates from a saturated solution at lower temperatures. Thus, it was necessary to carry out both of the CX and AX operations at medium to high temperatures (50 < T < 80 oC) and in the stirred vessels, instead of the fixed bed columns. We designed and tested 28 purification processes, whose difference was number of the employed CX, AX and RC stages, as well as the order of their appearing in the process. The obtained UPA in each process was analyzed for measuring of concentration of the major impurities. Out of the 28 examined processes, 4 could met the standard limits of the impurities for all of the checked ions. The next step of the project was finding optimum purification process between the aforementioned five options. Our criterion for such optimization was the overall economical balance. Three factors affecting economic balance were number of stages and yield of the process. The final selected process had the following abbreviated scheme: CX→AX →CX→AX→RC
  9. Keywords:
  10. Ion Exchange ; Purification ; Boric Acid ; Recrystallization ; Laboratary Study ; Nuclear Grade

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