The ⁴¹Ca bomb pulse and atmospheric transport of radionuclides

Abstract

The model has been applied to calculate the bomb pulses of 14C; 36C1; 41Ca; øøSr, and 137Cs. For the transport of radionuclides that are attached to aerosols such as 41Ca, 9øSr, and 137Cs, sedimentation (gravitational settling) in the upper stratosphere has been taken into account. It has been found that the deposition of bomb-produced 36C1 on the Earth's surface is delayed compared to that of øøSr by about 1 year because 36C1 stays gaseous in the stratosphere. The model can also be used to calculate the deposition of cosmogenic radionuclides, e.g.,36C1 and 1øBe, in their natural archives, such as polar ice sheets.

A Comparison of 36Cl Nuclear Bomb Inputs Deposited in Snow From Vostok and Talos Dome, Antarctica, Using the 36Cl/Cl− ratio

“…The fact that the detected 36 Cl/Cl − ratio peaks are synchronous with the nuclear test inventory shows that when the 3‐year atmospheric transport is integrated, this fraction may be immobile upon its deposition in snow, with no major time lag registered. Three possibilities may explain this immobile phase: Part of the nuclear signal deposited is in particulate form, that is, as Na 36 Cl, contrary to findings by Zerle et al (), and this portion is not totally transformed into H 36 Cl during transport or in the snowpack. The Na 36 Cl aerosol may be preserved in the stratosphere during its transport to Antarctica, and then only partially fractionated in the troposphere before being deposited in the snow.…”

Radiochemical determination of 41Ca in nuclear reactor concrete

“…Of these methods, AMS is the most sensitive; a 41 Ca/ 40 Ca ratio as low as 10 −15 can be measured by this method [9]. RIMS is also a sensitive method for the determination of 41 Ca, and a detection limit of 0.1 Bq/g has been reported for 41 Ca in concrete [9,10]. However, both of these two techniques are expensive, and normally not available for the routine analysis of waste samples.…”

“…41 Ca decays to the ground state of 41 K by pure electron capture, emitting X-rays and Auger electrons of very low energy (0.3-3.6 keV) [6] and can therefore be measured by X-ray spectrometry [7] and liquid scintillation counting (LSC) [6,8]. Mass spectrometry techniques such as accelerator spectrometry (AMS) [9,10] and resonance ionization mass spectrometry (RIMS) [10,11] have also been used for the determination of 41 Ca. Of these methods, AMS is the most sensitive; a 41 Ca/ 40 Ca ratio as low as 10 −15 can be measured by this method [9].…”

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

“…CaF 3 -has also been used to inject Ca to the AMS system, since KF 3 -ion is instable [151]. In principle, a 41 Ca/ 40 Ca ratio as low as 10 -15 can be measured by AMS, while the detection limit of 41 Ca is mainly effected by the procedure blank and 41 K interference, the reported detection limit is 10 -12~ 10 -13 for Ca/ 40 Ca ratio or 0.1 mBq/g for 41 Ca [149,150].…”