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Radioactive releases from nuclear waste repository in the tropical climate environment
Progress in Nuclear Energy, Vol. 37, No. 1-4, pp. 383-386, 2000 Q 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0149-1970/00/$ - see front matter
Pergamon www.elsevier.com/locate/pnucene
PII: s0149-1970(00)00075-5
RADIOACTIVE RELEASES FROM NUCLEAR WASTE REPOSITORY IN THE TROPICAL CLIMATE ENVIRONMENT
YUDI U. IMARDJOKO
Department of Engineering Physics, Gadjah Mada University Jl. Grafika 2, Sekip Utara, Yogyakarta, Indonesia, 55281 Phone (62-274) 902 120, Fax (62-274) 9022 lo,90 1926
ABSTRACT The spent nuclear fuel from any nuclear power plant poses danger to the public if not taken care sufficiently. This report discusses the potential releases of radioactive materials to the accessible environment when the waste form is in the format using Synroc-C developed by ANSTO. The environment under the study is tropical environment and the repository area is below the groundwater table. The computational model was developed and run using the computer code called Repository Integration Program (RIP) developed by the Golder Associates. The result is considered a very low release to the accessible environment. 0 2000 Elsevier Science Ltd. All rights reserved. 1. INTRODUCTION The spent nuclear fuel from any nuclear power plant must be disposed in the monitored repository for some period of time because it poses danger to the public when not managed sufficiently. The repository for disposing the spent nuclear fuel must be well selected for strong prevention toward degradation of the waste. The spent nuclear fuel is packed into waste package, which is used to immobilize the radioactive waste should it become degraded. This report discusses the preliminary assessment of the radioactive release using the waste form of Synroc-C developed by Australian Nuclear Science and Technology Organization (ANSTO) (Jostson et al., 1998). The use of Synroc-C is selected based on superiority of the proven immobilization capability over million of years (Ringwood et al., 1988). The tropical environment selected for this research is based upon the previous assessment by the author (Imardjoko, 1995, 1998; Imardjoko et al., 1996a, 1996b). The assessment shows that in the tropical climate has generally higher corrosion rates due to microbiologically induced corrosion because of constant high temperature throughout the year, and higher energy activation that will lead to higher corrosion rate as well. 383
384
Y. U. Imardjoko
2. METHODOLOGY The research method used in this study is: a The characteristics and the total number of the spent nuclear fuel a Physical parameters of Synroc-C 0 Environmental parameters of the tropical climate Developing a computational model of the repository using RIP code (Golder Assoc., 1997) 0 cl Running the model and adjust the failure probability of waste containers 0 Presenting and Discussing the results The typical spent nuclear fuel assembly is the Pressurized Water Reactor (PWR) fuel assembly. The number of spent nuclear fuel assemblies used in this study is shown in Table 1. The environmental properties used in this study are selected from the previous studies of the proposed Genting Island repository conducted by the author (Faculty of Mineral Tech., 1990; Triarso, 1995). The Genting Island is very dry island. Rock formation is basalt from the pre-tertiary age. The area is 135 Ha. The soil has an average pH of 5.6. The southern part is proposed to be the potential site of nuclear waste repository. Basically, the computational model of this repository is to determine the most likely probability function of the waste-form failure mechanism. In this case, the inner container failure mechanism is said to be uniform and the outer container failure mechanism is log-uniform. Because of the superiority performance of Synroc-C the quantity of distribution of the waste form can vary uniformly. It is the judgement to put inner failure distribution to be uniform. However, for the outer container, which can vary greatly due to environmental conditions and the length of time of exposure of radiation. The failure mechanism for the outer container is log-uniform. Two external events are considered in this study, they are flooding the repository and the earthquake. Groundwater is primary the mechanism of the release to the accessible environment. Table 1. Number of Spent Nuclear Fuel Assemblies Year 2015-2017 2017-2019 2019-2021 2021-2023 2023-2025 2025-2027 2027-2029 2029-203 1 2031-2033 2033-2035 2035-2037 2037-2039 2039-2041 204 l-2043 2043-2045 2045-2047 2047-2049 2049-205 1 2051-2053 2053-2055
Plant1 Plant2 Plant3 Plant4 Plant5 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0 0 0
0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0 0
0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0
0
0
0
Total number of spent nuclear fuel
0 0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0
0 0 0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256
Total 64 128 192 256 320 320 320 320 320 320 320 320 320 320 320 512 448 384 320 256 6080
Radioactive releases from nuclear waste repository
385
The physical properties of Synroc-C is shown in Table 2 (Golder Associates, 1997). They are needed to run the computational model.
Table 2. Physical Properties of Synroc-C Thermal Conductivity, 1OO’C 1 3.0 2.1 15% wt of HLW Fractional Thermal Expansion 1 10.5 x 10m6 10% wt HLW Young’s Modulus 203 Tensile Strength 56 & 13 (room temperature) 52 + 11 (340°C) Compression Strength 793 (room temperature)
The data on the table is needed to determine the waste form, which requires by the RIP computer code. The scenario is that the waste form experienced earthquake and flooding attacks. The probability of the earthquake is 1xl O-’and probability of flooding is 1xl O-‘. The model The length calculation the biota is
is run using 10,000 realizations and 5,000 time steps to ensure the accuracy of the calculation. of realization is 1~10~ years. The number of plot steps is 100. Table 3 shows the results of the based upon the assumption that the source of drinking water is from the underground water and not considered as ‘the potential effect for the dose calculation.
Table 3. The Mean Annual Release Rate (Bq/year) for Various Radionuclides Radionuclide Annual Exposure c-14 2.8x1o+5 Se-79 Tc-99 I-129
2.2x1o+5 1.2x 1o+7 2.9~10~
cs-135 Ra-226 U-234 Np-237
4.4x1o+5
Pu-239 Pu-240 Pu-242
7.0x10+’ 1.4x10+’ 2.1x1o+6
6.7x10+’
Transport of radionuclides in the saturated zone yields retardation of radionuclide migration due to sorption and dispersion. During this period of retardation, radioactive decay reduces the inventory of most radionuclides. It shows that Ra-226 and U-234 have high annual release rates compared to other radionuclides. isotopes do not retard significantly in the saturated zone. They have low retardation factors.
These
386
Y U. Imardjoko
3. DISCUSSION OF THE RESULTS Based upon the results, they show significantly that the releases are still below the regulations imposed of the releases to the environment. Whether this result is due to the superiority of Synroc-C or less conservative on modeling calculations, this remains to be determined.
REFERENCES Faculty of Mineral Technology (1990), Penelitian Lanjutan Mengenai Geologi dan Hidrogeologi Lapangan di P. Genting untuk Calon Lokasi Pembuangan Lestari Limbah Radioaktif, BATAN, Jakarta. Golder Associates (1997), RIP - Integrated Probabilistic Simulator for Environmental Systems - Theory Manual & User’s Guide, Golder Associates Inc., Washington. Imardjoko Y.U. (1995), Total System Performance Assessment of the Proposed High Level Radioactive Waste Repository at Genting Island Karimunjawa Indonesia, Ph.D. dissertution, ISU, Ames. Imardjoko Y.U., Santosa H.B., Sunarno, Prabaningrum N., Muharini A., Wijayanti E., Adiartsi M. (1996a), Critical Data Required to Potentially Investigate Genting Island as High-Level Radioactive Waste Repository Site Facility in Indonesia, Geological Problems in Radioactive Waste Isolation - Second Worldwide Review. Imardjoko, Y.U., Bullen D.B, Yatim S. (1996), Performance Assessment Modeling of the Proposed Genting Island Repository Facility, High Level Radioactive Waste Management, Las Vegas. Imardjoko, Y.U. (1998), Next Generation of High-Level Radioactive Waste Repository Concept - An Ocean Island Approach, 1Ifh Pacific Basin Nuclear Conference, Banff Springs, April. Jostson A., Vance E.R., Durance G. (1998), Advances in Synroc Development, Zlth Pacific Basin Nuclear Conference, Banff Springs, April. Ringwood A.E., Kesson S.E., Reeve K.D., Levins D.M., Ramm E.J. (1988), Radioactive Waste Forms for the Future, North-Holland. Triarso I. (1995), Potensi Terumbu Karang di Wilayah Taman Nasional Laut Karimunjawa, Jawa Tengah, MS. Thesis, Gadjah Mada University, Yogyakarta.
Pergamon www.elsevier.com/locate/pnucene
PII: s0149-1970(00)00075-5
RADIOACTIVE RELEASES FROM NUCLEAR WASTE REPOSITORY IN THE TROPICAL CLIMATE ENVIRONMENT
YUDI U. IMARDJOKO
Department of Engineering Physics, Gadjah Mada University Jl. Grafika 2, Sekip Utara, Yogyakarta, Indonesia, 55281 Phone (62-274) 902 120, Fax (62-274) 9022 lo,90 1926
ABSTRACT The spent nuclear fuel from any nuclear power plant poses danger to the public if not taken care sufficiently. This report discusses the potential releases of radioactive materials to the accessible environment when the waste form is in the format using Synroc-C developed by ANSTO. The environment under the study is tropical environment and the repository area is below the groundwater table. The computational model was developed and run using the computer code called Repository Integration Program (RIP) developed by the Golder Associates. The result is considered a very low release to the accessible environment. 0 2000 Elsevier Science Ltd. All rights reserved. 1. INTRODUCTION The spent nuclear fuel from any nuclear power plant must be disposed in the monitored repository for some period of time because it poses danger to the public when not managed sufficiently. The repository for disposing the spent nuclear fuel must be well selected for strong prevention toward degradation of the waste. The spent nuclear fuel is packed into waste package, which is used to immobilize the radioactive waste should it become degraded. This report discusses the preliminary assessment of the radioactive release using the waste form of Synroc-C developed by Australian Nuclear Science and Technology Organization (ANSTO) (Jostson et al., 1998). The use of Synroc-C is selected based on superiority of the proven immobilization capability over million of years (Ringwood et al., 1988). The tropical environment selected for this research is based upon the previous assessment by the author (Imardjoko, 1995, 1998; Imardjoko et al., 1996a, 1996b). The assessment shows that in the tropical climate has generally higher corrosion rates due to microbiologically induced corrosion because of constant high temperature throughout the year, and higher energy activation that will lead to higher corrosion rate as well. 383
384
Y. U. Imardjoko
2. METHODOLOGY The research method used in this study is: a The characteristics and the total number of the spent nuclear fuel a Physical parameters of Synroc-C 0 Environmental parameters of the tropical climate Developing a computational model of the repository using RIP code (Golder Assoc., 1997) 0 cl Running the model and adjust the failure probability of waste containers 0 Presenting and Discussing the results The typical spent nuclear fuel assembly is the Pressurized Water Reactor (PWR) fuel assembly. The number of spent nuclear fuel assemblies used in this study is shown in Table 1. The environmental properties used in this study are selected from the previous studies of the proposed Genting Island repository conducted by the author (Faculty of Mineral Tech., 1990; Triarso, 1995). The Genting Island is very dry island. Rock formation is basalt from the pre-tertiary age. The area is 135 Ha. The soil has an average pH of 5.6. The southern part is proposed to be the potential site of nuclear waste repository. Basically, the computational model of this repository is to determine the most likely probability function of the waste-form failure mechanism. In this case, the inner container failure mechanism is said to be uniform and the outer container failure mechanism is log-uniform. Because of the superiority performance of Synroc-C the quantity of distribution of the waste form can vary uniformly. It is the judgement to put inner failure distribution to be uniform. However, for the outer container, which can vary greatly due to environmental conditions and the length of time of exposure of radiation. The failure mechanism for the outer container is log-uniform. Two external events are considered in this study, they are flooding the repository and the earthquake. Groundwater is primary the mechanism of the release to the accessible environment. Table 1. Number of Spent Nuclear Fuel Assemblies Year 2015-2017 2017-2019 2019-2021 2021-2023 2023-2025 2025-2027 2027-2029 2029-203 1 2031-2033 2033-2035 2035-2037 2037-2039 2039-2041 204 l-2043 2043-2045 2045-2047 2047-2049 2049-205 1 2051-2053 2053-2055
Plant1 Plant2 Plant3 Plant4 Plant5 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0 0 0
0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0 0
0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0
0
0
0
Total number of spent nuclear fuel
0 0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256 0
0 0 0 0 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 256
Total 64 128 192 256 320 320 320 320 320 320 320 320 320 320 320 512 448 384 320 256 6080
Radioactive releases from nuclear waste repository
385
The physical properties of Synroc-C is shown in Table 2 (Golder Associates, 1997). They are needed to run the computational model.
Table 2. Physical Properties of Synroc-C Thermal Conductivity, 1OO’C 1 3.0 2.1 15% wt of HLW Fractional Thermal Expansion 1 10.5 x 10m6 10% wt HLW Young’s Modulus 203 Tensile Strength 56 & 13 (room temperature) 52 + 11 (340°C) Compression Strength 793 (room temperature)
The data on the table is needed to determine the waste form, which requires by the RIP computer code. The scenario is that the waste form experienced earthquake and flooding attacks. The probability of the earthquake is 1xl O-’and probability of flooding is 1xl O-‘. The model The length calculation the biota is
is run using 10,000 realizations and 5,000 time steps to ensure the accuracy of the calculation. of realization is 1~10~ years. The number of plot steps is 100. Table 3 shows the results of the based upon the assumption that the source of drinking water is from the underground water and not considered as ‘the potential effect for the dose calculation.
Table 3. The Mean Annual Release Rate (Bq/year) for Various Radionuclides Radionuclide Annual Exposure c-14 2.8x1o+5 Se-79 Tc-99 I-129
2.2x1o+5 1.2x 1o+7 2.9~10~
cs-135 Ra-226 U-234 Np-237
4.4x1o+5
Pu-239 Pu-240 Pu-242
7.0x10+’ 1.4x10+’ 2.1x1o+6
6.7x10+’
Transport of radionuclides in the saturated zone yields retardation of radionuclide migration due to sorption and dispersion. During this period of retardation, radioactive decay reduces the inventory of most radionuclides. It shows that Ra-226 and U-234 have high annual release rates compared to other radionuclides. isotopes do not retard significantly in the saturated zone. They have low retardation factors.
These
386
Y U. Imardjoko
3. DISCUSSION OF THE RESULTS Based upon the results, they show significantly that the releases are still below the regulations imposed of the releases to the environment. Whether this result is due to the superiority of Synroc-C or less conservative on modeling calculations, this remains to be determined.
REFERENCES Faculty of Mineral Technology (1990), Penelitian Lanjutan Mengenai Geologi dan Hidrogeologi Lapangan di P. Genting untuk Calon Lokasi Pembuangan Lestari Limbah Radioaktif, BATAN, Jakarta. Golder Associates (1997), RIP - Integrated Probabilistic Simulator for Environmental Systems - Theory Manual & User’s Guide, Golder Associates Inc., Washington. Imardjoko Y.U. (1995), Total System Performance Assessment of the Proposed High Level Radioactive Waste Repository at Genting Island Karimunjawa Indonesia, Ph.D. dissertution, ISU, Ames. Imardjoko Y.U., Santosa H.B., Sunarno, Prabaningrum N., Muharini A., Wijayanti E., Adiartsi M. (1996a), Critical Data Required to Potentially Investigate Genting Island as High-Level Radioactive Waste Repository Site Facility in Indonesia, Geological Problems in Radioactive Waste Isolation - Second Worldwide Review. Imardjoko, Y.U., Bullen D.B, Yatim S. (1996), Performance Assessment Modeling of the Proposed Genting Island Repository Facility, High Level Radioactive Waste Management, Las Vegas. Imardjoko, Y.U. (1998), Next Generation of High-Level Radioactive Waste Repository Concept - An Ocean Island Approach, 1Ifh Pacific Basin Nuclear Conference, Banff Springs, April. Jostson A., Vance E.R., Durance G. (1998), Advances in Synroc Development, Zlth Pacific Basin Nuclear Conference, Banff Springs, April. Ringwood A.E., Kesson S.E., Reeve K.D., Levins D.M., Ramm E.J. (1988), Radioactive Waste Forms for the Future, North-Holland. Triarso I. (1995), Potensi Terumbu Karang di Wilayah Taman Nasional Laut Karimunjawa, Jawa Tengah, MS. Thesis, Gadjah Mada University, Yogyakarta.