Fission product precipitation from the atmosphere in Debrecen, Hungary, between 1958 and 1960

Abstract

Observations concerning the atmospherical precipitation of fission products were r during 1958--1960. The cessation of nuclear test explosions since Nov. 1958 made it possible to approximately measure the clean up rate of fission products in the atmosphere. A mean residenee time of 0,45 years anda clean up half period of 0,3 years were observed. Owing to this, a reduetion of fission product contamination of the atmosphere to one hundredth of its original value can be expected within two years.The clean up therefore is much quicker, and the rate of mixing between stratosphere and troposphere seems to be more intense than anticipated. The fission product contamination decreases to 10% of its original value within one year. In this reduction the effect of the mixing between the air masses of the stratosphere and troposphere and the radioaetive decay are included. The mixing rate of the air masses of the stratosphere (or at least that of the Iower layers of it) is about 75% per year.The atmospherie precipitation has been observed without interruption and by the same methods at this Institute since 1952 [1], [2], [3], [4], [5]. The measurements we ate dealing with in this paper were made betwecn 1958 and 1960 and indicate a very rapid decrease of contamination since the cessation of nuclear test explosions in November 1958.The atmospheric preeipitation has been eollected eaeh morning, whenever there was any preeipitation in an ombrometer with a PVC funnel 40 cm in diameter. We suppose --in agreement with other authors [6] --that by sueh a sampling method practically the total fallout can be gathered. Most of the fallout is brought down by rain and snow. Dust fallout deposited on the funnel is mostly washed into the bottle by the next rain. The total water sample eontaining the dust and soot particles is removed from the bottle and eoneentrated by evaporation in a porcelain dish, then earried into a sample measuring glass cup of 25 mm inner diameter and 8 mm high. (For detailed description of methodics see ReŸ [4].)The sample is measured about 48 hours after collection by an endwindow GM counter 25 mm in diameter with ah aluminium window thickness ~)f 0,1 mm.The quantity of water and the measured activity is then reduced so as to refer to the dimensions of a normal meteorological ombrometer, i. e. to a surface of 1/50 m 2. In the earliest measurements (in 1952) a normal meteorological ombrometer was used, but later experience warranted a .,4eta Phys. Hung. Tom. XIII. Fase. 3,

Precipitation of fission products from the atmosphere in Debrecen, Hungary, during 1966 and 1967

“…3 shows the quarterly sums of the same data. A previous report [6] contains our results from the years 1952--1960in a similar graphical summary.…”

Fission product precipitation from the Atmosphere in Debrecen, Hungary, between 1963 and 1965

“…1 shows the results of our measurements carried out in the years 1963 to 1965. As in our previous works [4,6,7] collection surface of 1/50 rol Fig. 1 illustrates not only the total measurecl beta activity plottecl on the orclinate in cpm ancl in 10-11 Curie units but the quantity of claily precipitation, clownwards on the ordinate in mm rainfall ancl total collectecl water volume.…”

“…1 illustrates not only the total measurecl beta activity plottecl on the orclinate in cpm ancl in 10-11 Curie units but the quantity of claily precipitation, clownwards on the ordinate in mm rainfall ancl total collectecl water volume. Apart from the considerable amount of radioactive fallout in the first half of 1963 the results inclicate a rather marked clecrease of activity from 1963 on, with ah average clecontamination half periocl similar to that cleterminecl earlier [6]. The effect of increasecl exchange between the stratosphere and troposphere during springtime results in a markecl "spring peak" in total fallout cluring each year, the peak in 1963 being less prominent because of the presence and decay of shortlivecl fission proclucts.…”

“…The eessation of nuclear tests between 1958 and 1961 led to the conclusion that the decontamination of the stratosphere is much quicker than was antieipated [6]. Though in the years 1961 and 1962 a rather large amount of fission products (equivalent to a total yield of about 230 MT) was injected into the stratosphere, from the end of 1962 on, the fallout activity again strongly decreased, andas can be seen from Table 1, at the end of 1964 the total monthly activity decreased to a value of only 2,5--3 mC/km 2.…”

“…Measurements carried out to determine the fission product content of atmospheric precipitation was begun at this Institute in 1952 [1] [2] and was followed by the regular and uninterrupted observation of total fission product beta activity of precipitation during the following years [3,4,5,6,7].…”