Kolemanitli betonların nötron zırhlama etkinliğinin ve aktivitesinin incelenmesi

Abstract

code, ANITA, with the GREAC-ECN-5 cross section library for different neutron flux and irradiation conditions. The activity, dose and decay heat of concrete shields subject to hypothetical ly 20 years of stepwise and continuous irradiation are calculated. The decay of radio-isotopes for 10s years after shutdown were studied. At the end of the first irradiation step, colemanite concrete reaches saturation activity. It means, radioactive inventory of colemanite concrete are mostly composed of short-lived nuclei. At shutdown, the total activity of ordinary and colemanite concretes are almost the same. Predominant radio isotopes are A 1-28, N-16 and Aî - 37. These nuclei are due to some common elements found in concrete and colemanite has no great effect. If the shutdown radioactive inventory of both shields are compared, it is observed that the activities induced by common elements are very near to each other, but H-3, He-6, Li-8, Be-8, Be-10, Be-11. B-12 activities are increased in colemanite concrete. These nuclei are. directly or indirectly, imposed by boron reactions. Among them, only H3 seems to be important here because of its relatively long half-life and contribution to the activity.. Because of colemanite addition, mainly H,0,Ca nuclei are increased in concrete. Trace element composition of colemanite concrete is only 0.066 % by weight. The main difference between concrete compositions is 1.255 % of bor content of colemanite concrete. If the boron-neutron reactions are examined, it is observed that most of the reaction products are stable and the active ones have very small half-lives and immediately decay after shutdown. They have no decay gammas, thus not weighting the gamma dose problem. The decay characteristics of the total activity of concretes are different from each other. The difference is maximum around 10 years after shutdown. This is due to H-3 radio-isotopes. H-3 activity of colemanite concrete at shutdown is 11.3 times greater than ordinary concrete. Its half-live is 12.3 years and it is effective for 100 years («10 half-lives). After that time, both concretes have approximately the same activity. The most important reactions giving H-3 are caused by Li-6 and Li-7. Before irradiation, Li isotopes are not available in concrete composition and come out with xoB(n,na)sLi, 1°B(n,a),'Li reactions. The latter reaction's cross section with thermal neutron is very high. Thus, boron nuclei help indirectly to increase H-3 activity in colemanite concrete. XII

From the decommissioning point of view, colemanite concrete can be classified as high-level active waste at shutdown. Since, the most of the nuclei contributing to the shutdown activity of colemanite concrete are short-lived, it loses its activity very fast. 1 day after shutdown, 78.3 % of its activity decreases. 30 days after, 87.2 % and 1 year after, 97.2 % of its activity is decreased. Depending on the neutron flux level, 1-10 years after shutdown, colemanite concrete can be handled as middle- level active waste. 10s years later, it can be taken as low-level active waste. Gamma dose in colemanite concrete is lower than ordinary concrete. Although thermal neutron absorption increases due to the boron content of colemanite, secondary gamma ray generation does not aggravate. The most of the reaction products are stable. The active ones usually emit soft gammas attenuated in the shield. Colemanite concrete was compared two different concrete shields from the literature, containing colemanite and/or barite aggregates, under the same conditions. It is found that the shield thickness of colemanite-barite concrete must be ** 2 cm, that of barite concrete =» 17 cm more than colemanite concrete shield thickness. Among them, except ordinary Portland concrete, colemanite concrete has less shield volume, mass and cost. If the activities of these concretes are compared. It is observed that they are 2.7- 2.9 times more active than colemanite concrete at shutdown and reach its activity 20-50 years after shutdown. Consequently, by adding 10 wt. % of colemanite to high quality Portland concrete, thinner shields can be constructed. This material saving at the beginning of shield design is more important from the radioactive waste management point of view. Thinner shield means that less amount of radioactive waste will be handled and stored for final disposal. Thus, supplying economy in decommissioning cost. Colemanite addition does not aggravate the total activity of ordinary Portland concrete. The difference appears during the decay period because of H-3 activity. 100 years after shutdown, both concretes have the same activity. On the other and, colemanite content in concrete does not improve secondary gamma-ray and H gas production. These are also important for safety operation condition. Xlllcode, ANITA, with the GREAC-ECN-5 cross section library for different neutron flux and irradiation conditions. The activity, dose and decay heat of concrete shields subject to hypothetical ly 20 years of stepwise and continuous irradiation are calculated. The decay of radio-isotopes for 10s years after shutdown were studied. At the end of the first irradiation step, colemanite concrete reaches saturation activity. It means, radioactive inventory of colemanite concrete are mostly composed of short-lived nuclei. At shutdown, the total activity of ordinary and colemanite concretes are almost the same. Predominant radio isotopes are A 1-28, N-16 and Aî - 37. These nuclei are due to some common elements found in concrete and colemanite has no great effect. If the shutdown radioactive inventory of both shields are compared, it is observed that the activities induced by common elements are very near to each other, but H-3, He-6, Li-8, Be-8, Be-10, Be-11. B-12 activities are increased in colemanite concrete. These nuclei are. directly or indirectly, imposed by boron reactions. Among them, only H3 seems to be important here because of its relatively long half-life and contribution to the activity.. Because of colemanite addition, mainly H,0,Ca nuclei are increased in concrete. Trace element composition of colemanite concrete is only 0.066 % by weight. The main difference between concrete compositions is 1.255 % of bor content of colemanite concrete. If the boron-neutron reactions are examined, it is observed that most of the reaction products are stable and the active ones have very small half-lives and immediately decay after shutdown. They have no decay gammas, thus not weighting the gamma dose problem. The decay characteristics of the total activity of concretes are different from each other. The difference is maximum around 10 years after shutdown. This is due to H-3 radio-isotopes. H-3 activity of colemanite concrete at shutdown is 11.3 times greater than ordinary concrete. Its half-live is 12.3 years and it is effective for 100 years («10 half-lives). After that time, both concretes have approximately the same activity. The most important reactions giving H-3 are caused by Li-6 and Li-7. Before irradiation, Li isotopes are not available in concrete composition and come out with xoB(n,na)sLi, 1°B(n,a),'Li reactions. The latter reaction's cross section with thermal neutron is very high. Thus, boron nuclei help indirectly to increase H-3 activity in colemanite concrete. XIIFrom the decommissioning point of view, colemanite concrete can be classified as high-level active waste at shutdown. Since, the most of the nuclei contributing to the shutdown activity of colemanite concrete are short-lived, it loses its activity very fast. 1 day after shutdown, 78.3 % of its activity decreases. 30 days after, 87.2 % and 1 year after, 97.2 % of its activity is decreased. Depending on the neutron flux level, 1-10 years after shutdown, colemanite concrete can be handled as middle- level active waste. 10s years later, it can be taken as low-level active waste. Gamma dose in colemanite concrete is lower than ordinary concrete. Although thermal neutron absorption increases due to the boron content of colemanite, secondary gamma ray generation does not aggravate. The most of the reaction products are stable. The active ones usually emit soft gammas attenuated in the shield. Colemanite concrete was compared two different concrete shields from the literature, containing colemanite and/or barite aggregates, under the same conditions. It is found that the shield thickness of colemanite-barite concrete must be ** 2 cm, that of barite concrete =» 17 cm more than colemanite concrete shield thickness. Among them, except ordinary Portland concrete, colemanite concrete has less shield volume, mass and cost. If the activities of these concretes are compared. It is observed that they are 2.7- 2.9 times more active than colemanite concrete at shutdown and reach its activity 20-50 years after shutdown. Consequently, by adding 10 wt. % of colemanite to high quality Portland concrete, thinner shields can be constructed. This material saving at the beginning of shield design is more important from the radioactive waste management point of view. Thinner shield means that less amount of radioactive waste will be handled and stored for final disposal. Thus, supplying economy in decommissioning cost. Colemanite addition does not aggravate the total activity of ordinary Portland concrete. The difference appears during the decay period because of H-3 activity. 100 years after shutdown, both concretes have the same activity. On the other and, colemanite content in concrete does not improve secondary gamma-ray and H gas production. These are also important for safety operation condition. Xlllcode, ANITA, with the GREAC-ECN-5 cross section library for different neutron flux and irradiation conditions. The activity, dose and decay heat of concrete shields subject to hypothetical ly 20 years of stepwise and continuous irradiation are calculated. The decay of radio-isotopes for 10s years after shutdown were studied. At the end of the first irradiation step, colemanite concrete reaches saturation activity. It means, radioactive inventory of colemanite concrete are mostly composed of short-lived nuclei. At shutdown, the total activity of ordinary and colemanite concretes are almost the same. Predominant radio isotopes are A 1-28, N-16 and Aî - 37. These nuclei are due to some common elements found in concrete and colemanite has no great effect. If the shutdown radioactive inventory of both shields are compared, it is observed that the activities induced by common elements are very near to each other, but H-3, He-6, Li-8, Be-8, Be-10, Be-11. B-12 activities are increased in colemanite concrete. These nuclei are. directly or indirectly, imposed by boron reactions. Among them, only H3 seems to be important here because of its relatively long half-life and contribution to the activity.. Because of colemanite addition, mainly H,0,Ca nuclei are increased in concrete. Trace element composition of colemanite concrete is only 0.066 % by weight. The main difference between concrete compositions is 1.255 % of bor content of colemanite concrete. If the boron-neutron reactions are examined, it is observed that most of the reaction products are stable and the active ones have very small half-lives and immediately decay after shutdown. They have no decay gammas, thus not weighting the gamma dose problem. The decay characteristics of the total activity of concretes are different from each other. The difference is maximum around 10 years after shutdown. This is due to H-3 radio-isotopes. H-3 activity of colemanite concrete at shutdown is 11.3 times greater than ordinary concrete. Its half-live is 12.3 years and it is effective for 100 years («10 half-lives). After that time, both concretes have approximately the same activity. The most important reactions giving H-3 are caused by Li-6 and Li-7. Before irradiation, Li isotopes are not available in concrete composition and come out with xoB(n,na)sLi, 1°B(n,a),'Li reactions. The latter reaction's cross section with thermal neutron is very high. Thus, boron nuclei help indirectly to increase H-3 activity in colemanite concrete. XIIFrom the decommissioning point of view, colemanite concrete can be classified as high-level active waste at shutdown. Since, the most of the nuclei contributing to the shutdown activity of colemanite concrete are short-lived, it loses its activity very fast. 1 day after shutdown, 78.3 % of its activity decreases. 30 days after, 87.2 % and 1 year after, 97.2 % of its activity is decreased. Depending on the neutron flux level, 1-10 years after shutdown, colemanite concrete can be handled as middle- level active waste. 10s years later, it can be taken as low-level active waste. Gamma dose in colemanite concrete is lower than ordinary concrete. Although thermal neutron absorption increases due to the boron content of colemanite, secondary gamma ray generation does not aggravate. The most of the reaction products are stable. The active ones usually emit soft gammas attenuated in the shield. Colemanite concrete was compared two different concrete shields from the literature, containing colemanite and/or barite aggregates, under the same conditions. It is found that the shield thickness of colemanite-barite concrete must be ** 2 cm, that of barite concrete =» 17 cm more than colemanite concrete shield thickness. Among them, except ordinary Portland concrete, colemanite concrete has less shield volume, mass and cost. If the activities of these concretes are compared. It is observed that they are 2.7- 2.9 times more active than colemanite concrete at shutdown and reach its activity 20-50 years after shutdown. Consequently, by adding 10 wt. % of colemanite to high quality Portland concrete, thinner shields can be constructed. This material saving at the beginning of shield design is more important from the radioactive waste management point of view. Thinner shield means that less amount of radioactive waste will be handled and stored for final disposal. Thus, supplying economy in decommissioning cost. Colemanite addition does not aggravate the total activity of ordinary Portland concrete. The difference appears during the decay period because of H-3 activity. 100 years after shutdown, both concretes have the same activity. On the other and, colemanite content in concrete does not improve secondary gamma-ray and H gas production. These are also important for safety operation condition. Xlll