atw - International Journal for Nuclear Power | 05.2020

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atw Vol. 65 (2020) | Issue 5 ı May RESEARCH AND INNOVATION 270 | Fig. 2. Schematic of ITER LIM-OBB loop. Results SCRAM SS316 CPs mass on In-Flux surface (kg) CPs mass on Out-Flux surface (kg) ACPs activity on In-Flux surface (Bq/m 2 ) ACPs activity on Out-Flux surface (Bq/m 2 ) Contact dose rate of Out-Flux region (mSv/h) Contact dose rate of Out-Flux region after shutdown for 10 days (mSv/h) | Tab. 3. The calculation results of ACPs in ITER LIM-OBB loop. this paper, the continuous pulse method (CP) [14] is adopted to treat the pulses. The CP method is assumed to consist of a continuous irradiation period followed by only several pulses before shutdown, which has been proved accurate and efficient. 4.2 The calculation results and discussions The calculation results of ACPs activity in ITER LIM-OBB loop with CATE code are presented in Table 3. The structure materials in the In-Flux region lie well within the biological shield, and they pose no direct radiation hazard to operating personnel. While the equipments and loops in the Out-Flux region become more important, because the workers have to access to them for periodic inspection and maintenance, and exposed to γ radiation 3.087E+01 4.599E+01 2.225E+12 4.557E+09 3.621E+00 7.852E-02 2.078E+01 2.817E+01 1.700E+12 3.233E+09 2.314E+00 1.422E-01 from ACPs there, which may be a major contributor to ORE [15]. Therefore, only the dose rate of Out-Flux region is calculated, as follows in Table 4. From the above tables, some conclusions are drawn as follows. (1) During the operation phase of the reactor, the mass of corrosion products produced by SCRAM is more than SS316, which means the corrosion resistance of the traditional austenitic steel SS316 is better than SCRAM. (2) During the operation phase of the reactor, the activity of ACPs produced by SCRAM is more than SS316. This trend is consistent with the mass of corrosion products, which means ACPs activity is determined by the mass of corrosion products to some degree. (3) During the operation phase of the reactor, the contact dose rate of Out-Flux region produced by SCRAM is more than SS316. But during shutting down the reactor for 10 days, the contact dose rate of Out-Flux region produced by SS316 is more than SCRAM. This means SCRAM can present advantage on ORE decrease during the shutdown phase rather than the operation phase, compared with the traditional austenitic steel SS316. (4) The fast decrease of dose rate of SCRAM after shutdown is due to its nuclide composition of ACPs. SCRAM doesn’t contain Co element, and thus activation products of Co (long-lived nuclides Co-57, Co-58 and Co-60) do not exist in ACPs. But for SS316 with Co element, the activation products of Co, especially Co-58, contribute a large part to the dose rate, and result in the relative slow decrease of dose rate after shutdown. 4 Conclusions In this paper, firstly the corrosion rate of Super-clean Reduced Activation Martensitic (SCRAM) steel under ITER operation conditions was measured using a high-temperature flowing-water corrosion experiment loop. Then the model of ITER LIM-OBB loop was simulated by the ACPs source term analysis code CATE, and the nuclide composition and space distribution of ACPs of SCRAM and SS316 were calculated. These results were introduced to the dose rate analysis code ARShield, and the contact dose rate of Out-Flux region in ITER LIM-OBB loop caused by ACPs was calculated. At last, some comparisons among SCRAM and SS316 were made from the point of view of ORE. The results showed that compared with SS316, SCRAM produced higher dose rate during the operation phase of the reactor because of the bad corrosion resistance, but during the shutdown phase, it presented advantage on ORE decrease due to its good activation resistance. Acknowledgments The authors would like to express their gratitude for the support: Project 11605058 supported by National Natural Science Foundation of China and Project 2017MS041 supported by the Fundamental Research Funds for the Central Universities. Research and Innovation The Performance of Low Activation Steel SCRAM on ACPs Source Term in Water- cooled Loop of Fusion Reactor ITER ı Weifeng Lyu, Jingyu Zhang and Shouhai Yang
atw Vol. 65 (2020) | Issue 5 ı May Nuclide References Half-life (h) [5] A. Rocher, J. L. Bretelle, M. Berger: Impact of main radiological pollutants on contamination risks (ALARA) optimization of physico chemical environment and retention technics during operation and shutdown, in Proceedings of the European Workshop on Occupational Exposure Management at NPPs (ISOE 04), Session 2, EDF, Lyon, France, March 2004. [6] C.B.A. Forty, P.J. Karditsas: Preliminary cooling circuit activation and ORE assessment for ITER, Paper presented at 19 th SOFT, Lisbon, September16-20, 1996. [7] Q. Huang, J. Li, Y. Chen: Study of irradiation effects in China low activation martensitic steel CLAM, Journal of Nuclear Materials, vol. 329, pp. 268-272, 2004. [8] ITER Group: ITER technical basis, ITER EDA Documentation Series No. 24, IAEA, Vienna, 2002. [9] T. Muroga, M. Gasparotto, and S.J. Zinkle: Overview of materials research for fusion reactors, Fusion Engineering and Design, vol. 61, pp. 13-25, 2002. [10] Y. Wen, S. Jin, Z. Yang, F. Luo, Z. Zheng, L. Guo, J. Suo: Positron beam Doppler broadening spectra and nanohardness study on helium and hydrogen irradiated RAFM steel, Radiation Physics and Chemistry, vol. 107, pp. 19-22, 2015. [11] V. Belous, G. Kalinin, P. Lorenzetto, S. Velikopolskiy: Assessment of the corrosion behaviour of structural materials in the water coolant of ITER, Journal of Nuclear Materials, vol. 258, pp. 351-356, 1998. [12] P. J. Karditsas: Activation product transport using TRACT: ORE estimation of an ITER cooling loop, Fusion Engineering and Design, vol. 45, no. 2, pp. 169-185, 1999. [13] J. Zhang, L. Li, Y. Chen: Application of CATE 2.0 Code on Evaluating Activated Corrosion Products in a PWR Cooling Loop, ATW-International Journal for Nuclear Power, vol. 62, no. 3, pp. 181-185, 2017. [14] R.A. Forrest: The European Activation File: EAF-2007 decay data library, UKAEA FUS 537, 2007. [15] R.A. Forrest, J. Kopecky, J-Ch. Sublet: The European Activation File: EAF-2007 neutron-induced cross section library, UKAEA FUS 535, 2007. [16] S. He, Q. Zang, J. Zhang, H. Zhang, M. Wang, Y. Chen: Development and Validation of an Interactive Efficient Dose Rates Distribution Calculation Program Arshield for Visualization of Radiation Field in Nuclear Power Plants, Radiation Protection Dosimetry, vol. 174, no. 2, pp. 159-166, 2017. [17] ITER-JCT: ITER Generic Site Safety Report (GSSR), Volume III: Radiological and energy source terms, ITER G84 RI 3 01-07-13 R 1.0, 2001. [18] J. Sanz, O. Cabellos, P. Yuste, S. Reyes, J.F. Latkowski: Pulsed activation of structural materials in IFE chambers, Fusion Engineering and Design, vol. 60, no. 1, pp. 45-53, 2002. [19] C.B.A Forty, J.D. Firth, G.J. Butterworth: Influence of materials choice on occupational radiation exposure in ITER, Journal of Nuclear Materials, vol. 258, pp. 335-338, 1998. Contact dose rate (mSv/h) Authors Weifeng Lyu Shouhai Yang Senior engineers State Key Laboratory of Nuclear Power Safety Monitoring Technology and Equipment, Shenzhen, Guangdong, 518172, China Jingyu Zhang Associate professor School of Nuclear Science and Engineering, North China Electric Power University No.2, Beinong Road, Changping District, Beijing 102206, China Contact dose rate 10 days after shutdown (mSv/h) SCRAM SS316 SCRAM SS316 MN-56 2.579E+00 3.518E+00 1.907E+00 -- -- NI-57 3.560E+01 -- 1.805E-01 -- -- V-52 6.238E-02 1.809E-03 2.470E-03 -- -- CR-51 6.648E+02 6.614E-03 7.827E-03 4.412E-03 4.257E-03 MN-54 7.489E+03 8.692E-02 8.410E-02 7.282E-02 5.746E-02 CO-57 6.522E+03 -- 1.447E-03 -- 9.851E-04 CO-58 1.701E+03 -- 1.135E-01 -- 7.189E-02 CO-60 4.618E+04 -- 8.450E-03 -- 5.882E-03 FE-59 1.068E+03 1.720E-03 1.407E-03 1.074E-03 8.408E-04 | Tab. 4. The main contributors to dose rate. RESEARCH AND INNOVATION 271 Research and Innovation The Performance of Low Activation Steel SCRAM on ACPs Source Term in Water- cooled Loop of Fusion Reactor ITER ı Weifeng Lyu, Jingyu Zhang and Shouhai Yang
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