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<p>This study calculates neutron activation rate and elemental activity in reactor building concrete using SuperMC-3.4 software with the Chebyshev Rational Approximation Method (CRAM). Major elements such as Co, Fe, Ca, Ni, and C were analyzed over 60 years of reactor operation plus 5 years of cooling period. Co-60 and Ni-62 remain significant contributors to gamma dose even after prolonged cooling. The total gamma dose rate at the biological shield decreased from 6.8 mSv/h at shutdown to 0.42 mSv/h after 5 years (a reduction of 93.8%). Consequently, the activity of Co-60 decreased from 1.2 × 10<sup>5</sup> to 7.6 × 10<sup>3</sup> Bq/cm<sup>3</sup>. The results demonstrated that decommissioning after 60 years of operation plus 5 years of cooling meets the requirements of IAEA-GSR Part 6, maintains occupational exposure below the ICRP limits (20 mSv/year with protective measures), and supports ALARA-compliant radiation protection planning. To estimate the required shielding thickness, a standard lead apron (0.5&#xa0;mm Pb) resulted in a dose reduction of approximately 20%. Also, mobile lead barriers (50&#xa0;mm) led to a dose reduction of approximately 50%. Using combined shielding could achieve a potential reduction of 70–80%, thus enabling extended operation near concrete surfaces. Compared to international standards, the gamma dose rate at shutdown and after 5 years showed good agreement with reported reference values (deviation ± 9%) for various plant types, confirming the effectiveness of CRAM implementation.</p>

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Activation analysis of reactor building concrete for nuclear power plant decommissioning using the Chebyshev method

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月28日

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  • Abdollah Khorshidi,
  • Behzad Khosrowpour,
  • Seyed Hamed Hosseini,
  • Vahid Jamshidi

摘要

This study calculates neutron activation rate and elemental activity in reactor building concrete using SuperMC-3.4 software with the Chebyshev Rational Approximation Method (CRAM). Major elements such as Co, Fe, Ca, Ni, and C were analyzed over 60 years of reactor operation plus 5 years of cooling period. Co-60 and Ni-62 remain significant contributors to gamma dose even after prolonged cooling. The total gamma dose rate at the biological shield decreased from 6.8 mSv/h at shutdown to 0.42 mSv/h after 5 years (a reduction of 93.8%). Consequently, the activity of Co-60 decreased from 1.2 × 105 to 7.6 × 103 Bq/cm3. The results demonstrated that decommissioning after 60 years of operation plus 5 years of cooling meets the requirements of IAEA-GSR Part 6, maintains occupational exposure below the ICRP limits (20 mSv/year with protective measures), and supports ALARA-compliant radiation protection planning. To estimate the required shielding thickness, a standard lead apron (0.5 mm Pb) resulted in a dose reduction of approximately 20%. Also, mobile lead barriers (50 mm) led to a dose reduction of approximately 50%. Using combined shielding could achieve a potential reduction of 70–80%, thus enabling extended operation near concrete surfaces. Compared to international standards, the gamma dose rate at shutdown and after 5 years showed good agreement with reported reference values (deviation ± 9%) for various plant types, confirming the effectiveness of CRAM implementation.