International Edition ISSN Volume 14 (2012), No. 2 March

Transcription

1 POWERPLANT CHEMISTRY International Edition ISSN Volume 14 (2012), No. 2 March ABSTRACTS Further Experience with Amine Form Operation of Deep Bed, Full Flow Condensate Polishers at Millstone Power Station Lewis E. Crone This paper reports on a process for converting and operating deep bed condensate polishing resins in the amine form that has been designed, tested, and implemented at Dominion's Millstone Power Station. The plant employs amine form polishers as part of a strategy to reduce balance of plant corrosion and iron transport, while continuously providing protection of the primary pressure boundary inside the steam generators from chemical assault in the event of a condenser tube leak. Over the last year, Millstone Unit 2 (MP2) has been able to elevate secondary cycle ph to a level congruent with non-polishing plants, and the corresponding decrease in iron transport has allowed Millstone 2 to enter the industry top decile for final feedwater iron concentration. The paper describes the method by which MP2 was able to increase ph using a combination of hydrazine injection and full flow amine form polishers, and the effect on steam generator and balance of plant control parameters. PPChem 2012, 14(3), 1/5

2 Amine Chemistry Update on Impact on Resin Gregory Bachman, Douglas Kellogg, and Marty Wilkes Impurity removal in the steam cycle and the associated prevention of corrosion and/or fouling of system components are the goals of ion exchange resins. However, in many instances (such as a switch to amine chemistry or a change in product specifications), resins do not remove, and, in fact, contribute impurities to the steam cycle. This paper reviews recent data compiled to determine the direct and indirect effects of amines on ion exchange resins used in the power industry. Water chemistries have improved in recent years, in large part due to changes in chemistry and resins, but it is necessary to continue to develop products, processes and techniques to reduce impurities and improve overall water chemistry in power plant systems. Cycle Chemistry Monitoring Systems Pavel M. Gotovtsev and Viktor N. Voronov One of the tasks of water chemistry control and monitoring at fossil power plants is prevention of water chemistry failure. This aim may be achieved by prediction of impurity concentrations in different parts of the cycle and calculation of the water chemistry parameters that cannot be measured directly by standard analyzers. One of the ways to accomplish these tasks is based on mathematical modeling of the water chemistry state with application of artificial neural networks (ANNs). This article gives a brief introduction to this topic and shows examples and problems of mathematical modeling of water chemistry and ANN applications. PPChem 2012, 14(3), 2/5

3 Impact of Load-Follow Operation on the Chemistry of the Primary and Secondary Circuits of a Pressurized Water Reactor Michael Bolz and Andreas Speck In Germany, renewable energy forms have priority in being fed to the grid. More and more load operation of the nuclear power plants still in operation is necessary to stabilize the grid. This report summarizes the deviations in the chemical parameters experienced one particular weekend, when one nuclear power plant had to reduce power from full load (1 465 MW) to MW and 860 MW, and generally assesses the expected impact of load-follow operation on chemistry and radiology. It concludes that if possible changes in the behaviour of the corrosion products and the corrosion process are monitored with an effective surveillance programme so that deviations can be addressed in time to take appropriate countermeasures, nuclear energy and renewable energies can complement each other. PPChem 2012, 14(3), 3/5

4 Chloride Contamination of the Water/Steam Cycle in Power Plants Part II. Evidence for Two Previously Unknown Routes from Condenser Cooling Sources Emmanuel K. Quagraine and Jonathan P. Ruffini This is the second paper in a series of publications on findings from investigations performed at the Shand Power Station of SaskPower to identify the root cause(s) of chloride contamination of the water/steam cycle experienced in the plant, which appeared quite elusive initially. In the first paper, we showed a case where the chloride ingress could not be explained by the current literature reported routes of chloride ingress. In this current paper, photographic evidence and sample test analyses both qualitative and quantitative by methods such as N, N-diethyl-p-phenylenediamine (DPD) reagent spectrometric determination for residual chlorine, scanning electron microscopy energy dispersive spectroscopy, inductively coupled plasma mass spectrometry, and combustion ion chromatography (AQF- IC) determination of anions are presented to support a hypothesis that chloride ingress was emanating from the re-circulating condenser cooling water, but by a pathway(or pathways) completely different from the traditionally known condenser tube water leaks. Evidence is provided that residual chlorine compounds and/or chlorides were ingressing in both gaseous forms and aqueous forms into the condenser hotwell through weak seals of tube-to-tubesheet joints. The latter route, via a water-borne pathway, was shown to be distinctly different from that of the well-known condenser tube leaks by means of condensate contamination; it appears to follow a mechanism based on solubility differences to selectively contribute more chloride than sulphate from cooling water sources into the hotwell water. It was however determined to be only a minor contributor. The former route, however, was implicated as the dominant route. By this pathway, chlorinated species of relatively high vapour pressures (some of which are strong oxidizing agents) would ingress into the condensate portion of the condenser via tubeto-tubesheet joints. Dezincification of the brass tubesheet was found to be likely to occur by this means, causing deposition of ZnO at the point of contact on the condensate side of the condenser as observed. PPChem 2012, 14(3), 4/5

5 Evaluation of the Applicability of AVT(O) Feedwater Treatment to Cycles with HRSGs Masamichi Miyajima, Yoshiaki Itou, Hiroaki Yamamoto, Senichi Tsubakizaki, Noboru Kawai, and Hiroshi Takaku In Japan, all-volatile treatment will be continued to be used even if hydrazine injection must be stopped, because the condenser performance is usually excellent. For the first time in Japan, we have conducted demonstration tests of the applicability of the oxidizing all-volatile treatment, AVT(O), without hydrazine due to concerns about the carcinogenicity of this chemical. No difference has been observed in water quality parameters such as the dissolved oxygen and the total iron concentrations between reducing allvolatile treatment, AVT(R), and AVT(O), and also no difference in the corrosion damage to the system equipment has been observed between the two water treatments. Furthermore, for heat recovery steam generators stored with water containing hydrazine during lay-up/outage, laboratory and power plant tests with hydrazine-free water have clearly shown that corrosion prevention is possible if the ammonia concentration is 50 mg L 1 for less than one month and also 100 mg L 1 for longer than one month. Based on these results, the application of AVT(O) has begun in several systems (14 units/3 400 MW) at Chubu Electric Power Co. PPChem 2012, 14(3), 5/5