Trace Elements with Large Activation Cross Section in Concrete Materials in Japan

Abstract

Amounts of trace elements with large activation cross section in concrete materials were measured to offer the basic data for developing of low activation concrete. From the measurements, the quantities of the activated radioactivities in biological shielding concrete were measured and evaluated for the clearance level.The average concentrations of 60 Co, 152 Eu and 134 Cs formed in concrete were 21.9, 1.08 and 3.21 ppm, respectively. The combination of the concrete materials for the most lowering concentrations of 60 Co, 152 Eu and 134 Cs was the limestone as aggregate and the white Portland cement produced in specific places. The most lowering concentrations of this limestone concrete were 0.16, 0.049 and 0.060 ppm, respectively. The limestone concrete was excellent as biological shielding concrete, because the neutron shielding effect was excellent a little compared with ordinary concrete. If this concrete used for biological shielding concrete, concrete waste will be able to handle as follows. Usage of this limestone low-activated concrete makes almost all concretes satisfy the clearance level for 60 Co after 20 yr cooling from decommissioning. In respect of 152 Eu, radioactivation quantity in the biological shielding concrete is reduced up to a half of the average value or less. With regard to 134 Cs, all concrete satisfies the clearance level.

Assessment of Long Lived Isotopes in Alkali-Silica Resistant Concrete Designed for Nuclear Installations

“…The dominant long-lived residual radioisotopes induced in concrete, which occupy 99–100% of the total residual radioactivity, are 60 Co, 152 Eu and 154 Eu [ 4 ]. Current investigations, based on NAA, revealed that the 60 Co and 152 Eu isotope contents in analyzed aggregate partly coincide with results for Japanese [ 5 , 35 ] and Indian [ 36 ] research; Figure 10 . Various rocks were collected from all over Japan and analyzed by Suzuki et al [ 5 ].…”

“…Current investigations, based on NAA, revealed that the 60 Co and 152 Eu isotope contents in analyzed aggregate partly coincide with results for Japanese [ 5 , 35 ] and Indian [ 36 ] research; Figure 10 . Various rocks were collected from all over Japan and analyzed by Suzuki et al [ 5 ]. They analyzed the trace elements of 60 Co, 152 Eu and 134 Cs.…”

“…From the results of screening tests for neutron irradiation, Kinno et al [ 35 ] found that the aggregate for low-activation concrete was quartzite with the lowest concentration of 60 Co = 0.1 ppm and 152 Eu = 0.004 ppm and limestone ( 60 Co = 0.08 ppm and 152 Eu = 0.05 ppm). According to Suzuki et al [ 5 ], the aggregate made from quartzite rock exhibited the lowest induced activity on neutron irradiation among all tested silica aggregates. The mean concentration of 60 Co was 3.55 ppm and 152 Eu 0.297 ppm.…”

“…The dominant long-lived residual radioisotopes induced in ordinary concrete at the time of decommissioning, which occupy 99–100% of the total residual radioactivity in terms of CL value, are 60 Co, 152 Eu and 154 Eu [ 4 , 5 ]. The representative single value of the clearance level and half-life are, respectively, CL 60 Co = 0.3 Bq/g, T 1/2 = 5.275 years, CL 152 Eu = 0.3 Bq/g, T 1/2 = 13.54 years, and CL 154 Eu = 0.3 Bq/g, T 1/2 = 8.59 years.…”

Elemental Analysis of Raw Materials of Nuclear Reactor Shielding to Develop Low Activation Concrete

“…are of great concern in the disposal of shielding materials used in nuclear reactor. Several calculations and experimental studies have been done to study the effect of neutron activation on the concrete shielding during the investment or after decommissioning of a 8 nuclear facility [5][6][7][8]. The radioactive isotopes due to the major elements such as Al, Ca, Na, Mg and Si will not be taken into account because after a short interval of time they will not be effective for residual activity [9,10].…”