Chinese Nuclear Explosion Research Articles

The density jump across the ICB and constraints on P‐reflector in the D' layer from observation of the 1992 Chinese Nuclear Explosion

Seismic waves observed from the Chinese nuclear explosion detonated on May 21, 1992 (mb=6.6) are analyzed to detect PKiKP and PdP, reflected waves from the inner core boundary (ICB) and the D” discontinuity, respectively. A linear stacking method is applied to a large number of digital data recorded in the Japanese Islands to identify the reflected waves. The stacked data indicate a weak signal of PKiKP. PKiKP/PcP amplitude ratio of 0.03 is obtained from the stacked waveforms of PKiKP and PcP, which suggests the density jump across the ICB to be 0.6 g/cm³. This value is in agreement with previous estimates from free oscillations data. No positive evidence for the identification of PdP is suggested from the stacking process. This implies the absence of a significant P wave reflector or, if present, the impedance contrast is less than 2% in the lowermost mantle under East China. Another interpretation in terms of gradient zone thickness or reflector topography is also possible.

Short and medium effects on the environment of Valencia, Spain, of the chernobyl nuclear plant accident

As a consequence of the 26 April 1986 accident at the Chernobyl nuclear plant, a large amount of radioactivity was released into the atmosphere. The radioactive plume formed could be detected in practically the whole of the Northern Hemisphere a few days later. The zone most affected by the radioactive cloud over Spain was that of the Mediterranean coast and the Balearic Islands. In this paper, the authors examine the level of the radioactive contamination reached in various receptive media in Valencia, such as air, dry-fallout, water, soil, grass and milk samples collected in Valencia immediately after the accident. The activity levels are compared with those found during 1964 and 1965 due to the Chinese nuclear atmospheric explosions. The levels of contamination presented by four species of migratory birds which spend the winter in this area is analyzed. Lastly, an estimate is made of the absorbed dose.

Determination of fissile materials in highly radioactive particles using a solid-state track detector method

Highly radioactive fallout particles collected from the 19th Chinese nuclear explosion test in the atmosphere were subjected to neutron irradiation in a reactor after being sandwiched with mica detectors. Star-like fission track patterns were revealed on the etched surface of the mica detectors. Uranium or plutonium could cause such prominent track patterns within the particles. Simple chemical separation procedure was applied for uranium and plutonium and both resultant fractions were examined with similar, highly sensitive fission tracking detection. Subsequently, a representative track pattern from a black spherical particle was analyzed for the determination of fissile nuclide content by comparing the total evaluated track numbers on the basis of the numerical calculation of track densities with the employed total thermal neutron fluence. The results implied that the uranium is responsible for the main fissile nuclide remaining within a particle as unfissioned fractions and should certainly be enriched with respect to235U within such small fallout particles.

Radionuclide concentrations in several seaweeds and their annual variations

To examine the radionuclide concentrations in the environment, seaweeds were collected once a year since 1976 at two different places. A marked change was observed in the number of radionuclides in seaweeds. The increase of radionuclides is attributed to contamination by radioactive fallout from Chinese nuclear explosion tests. The radionuclide concentrations were strongly dependent on the species of seaweeds. A gradual decrease of the137Cs/40K activity ratio was observed in spite of the input of additional137Cs fallout from Chinese nuclear tests. This implies that the amounts of137Cs introduced into seawater by these detonations were small in comparison with those already contained in seawater. The cesium content in seawater was estimated by using specific activities of137Cs in seaweeds and137Cs concentration in seawater. The results show good agreement with the reported values by direct analysis of seawater.

The detection of the 21st Chinese nuclear explosion in eastern Canada.

Measurements of the radioactive fallout from the 21 st atmospheric test by the People's Republic of China are presented, discussed and compared with those of the two previous Chinese nuclear explosions. The nationwide daily monitoring carried out by the Canadian Department of Health and Welfare could not detect any activity in surface air and precipitation that could be attributed to the test. We could detect it by collecting the sludge in water filtration plants, a sampling technique that we have been using to study the radioactivity in waters. The measurements were done on sludge collected at the Charny and Ste. Foy water filtration plants, fed respectively by the Chaudiere and the St. Lawrence rivers. The rivers are located in eastern Canada. Comparison of these measurements with those carried out since October 1977 on sludge indicates that the fallout intensity was in the ratio of 0.1: 1.0: 1.5 for the 21 st, 20th and 19th tests respectively.

Fallout 239Pu, 240Pu and 90Sr in surface-air in Ibaraki-Prefecture, Japan.

Measurements of 239, 240Pu and 90Sr were performed on air-dust samples collected by means of filtration with cellulose-asbestos filter at Ibaraki prefecture, Japan during 1974 to 1979. The ranges of 239, 240Pu and 90Sr content determined in these samples are 0.041-1.9 microBq/m3-air (1.1-52 aCi/m3-) and 2.3 87 microBq/m3-air (0.062-2.3 fCi/m3) respectively. The activity ratios of 239, 240Pu/90Sr are found to be in a range between 0.008 to 0.026 with a mean value of 0.017. General trend on time variation of the content of 239, 240Pu and 90Sr in the surface air was in similar pattern each other. The content of these nuclides increased after the Chinese nuclear test explosions, and also in spring seasons with the exception of a few cases.

Persistence of Cesium-137 in Arctic Lichens, Dryas integrifolia, and Lake Sediments

Samples of soils and plants collected at various locations in the Canadian Arctic for biomass and primary production study were also tested for radioactive contamination arising from nuclear weapons testing. Measurements with a gamma ray spectrometer showed that all the organic samples were contaminated with cesium-137, whereas the soils were relatively free of this isotope. A surprisingly high level of cesium-137 was observed in the fine organic sediments taken from a high-arctic oligotrophic lake. The radial distribution of cesium-137 in an rctic cushion plant, Dryas integrifolia, was determined and used to confirm a dating procedure for this type of plant. Samples collected in 1977 show radioactive contamination due to the Chinese nuclear explosion of September 1976. 26 references, 4 figures, 2 tables.

Determination of Fallout Nuclides by the 19th Chinese Nuclear Explosion Test

This paper describes analysis of the fallout from the 19th Chinese nuclear explosion test. 1. The analysis identified the following 16 nuclides using the radioactive decay method: 95Zr, 95Nb, 97Zr, 97Nb, 99Mo, 99mTc, 131I, 132Te, 1321, 133I, 137Cs, 140La, 143Ce, 147Nd, 237U and 239Np.2. Assessment of a baby's thyroid dose by radioiodine based on this nuclear explosion test was carried out. Culculated dose is 4.5 mrem/yr which is nearly one-third of radioiodine release guideline for a light-water-cooled nuclear power station.3. Nuclide concentration, (number of nuclides)/(nuclear fission yield), going back to predicted fission time was calculated. Assuming the fast fission of 239Pu, the concentration curves of each nuclide crossed at approximately the same point.The reported fission time by ERDA of U.S.A. fell into the authors' speculated fission time region which was calculated from the time dependent nuclide concentration curves mentioned above.4. The 237U was identified from the decay curves of 239Np photopeak (278 keV) and of multiplet of 239Np and 237U (207 keV). The estimated atomic ratio of 239Np: 237U at fission time was 28: 1.

Determination of Fallout Nuclides by the 19th Chinese Nuclear Explosion Test

This paper describes analysis of the fallout from the 19th Chinese nuclear explosion test. 1. The analysis identified the following 16 nuclides using the radioactive decay method: 95Zr, 95Nb, 97Zr, 97Nb, 99Mo, 99mTc, 131I, 132Te, 1321, 133I, 137Cs, 140La, 143Ce, 147Nd, 237U and 239Np.2. Assessment of a baby's thyroid dose by radioiodine based on this nuclear explosion test was carried out. Culculated dose is 4.5 mrem/yr which is nearly one-third of radioiodine release guideline for a light-water-cooled nuclear power station.3. Nuclide concentration, (number of nuclides)/(nuclear fission yield), going back to predicted fission time was calculated. Assuming the fast fission of 239Pu, the concentration curves of each nuclide crossed at approximately the same point.The reported fission time by ERDA of U.S.A. fell into the authors' speculated fission time region which was calculated from the time dependent nuclide concentration curves mentioned above.4. The 237U was identified from the decay curves of 239Np photopeak (278 keV) and of multiplet of 239Np and 237U (207 keV). The estimated atomic ratio of 239Np: 237U at fission time was 28: 1.

Long term survey on food pollution and contamination by radioactive fallout in Fukuoka, Japan (1961-1976) (author's transl)

The contamination and the pollution of foodstuffs by radioactive fallout have been investigated since 1961 in Fukuoka city and its suburban area. The results obtained were as follows.1) Recently, the degree of the contamination of greens by radioactive fallout which fell on the leaves decreased to one thousandth in the early stage of the investigation (1961-1962). In the period of the investigation, the remarkable increase of the radioactivity of fallout was observed within a week after the Chinese nuclear bomb explosion in the atmosphere (1st, 2nd, 5th, 12th, 13th, and 15th). The radioactivity was 2 to 300 times higher than the usual level.2) The radioactivity was not remarkable in vegetables which were washed with soap, but it decreased gradually year by year. The increase of the radioactivity was also observed a few days after the atmospheric nuclear explosion.3) In milk, there were no remarkable yearly decreases of the radioactivity from the beginning of the investigation, but the seasonal variations of the radioactivity, such as higher in April and May, were observed.4) The radioactivity in diets based on the standard food production in Japan was the highest in 1967. It decreased gradually from 1967 to 1971 and after that the remarkable variation of the activity was not observed.5) 137Cs contamination of foodstuffs has been observed quantitatively by the method of gamma spectrometry, while sometimes 95Zr-95Nb, 103Ru, and 131I were also detected from the specimens obtained immediately after the nuclear explosions.

Radioactive hot particles from the recent Chinese nuclear weapons tests

Variations in the number of individual fallout particles in the ground-level air at Fayetteville (36°N, 94°W), Arkansas, were measured for a period of about seven months after the 13th (January 7, 1972) and the 14th (March 18, 1972) Chinese nuclear test explosions. The fallout from the 13th test was typical of a tropospheric injection of debris and the effect lasted only for about five weeks, but the fallout from the 14th test persisted for about five months until August 1972, indicating that the fresh debris entered the stratosphere. The diameters of the particles ranged from about 0.1 to 7 μm in diameter, but a single unusually large particle (34 μm in diameter) was found during the night of March 23, 1972. Radiochemical studies were made on this 34-μm particle, in which the fission products belonging to the ‘volatile’ mass chains 89, 90, 91, 140, and 141 were highly depleted. The formation interval Ξ of this particle was calculated from the extent to which the volatile fission decay chains were depleted. A value very close to Ξ = 0 (second) was obtained from the mass 91 chain, but no positive Ξ values could be calculated from mass 140 and 141 chains. This discrepancy was explained as being due to the difference in the melting points of the oxides, of the elements belonging to the fission product decay chains (e.g., Rb, Cs, Sr, and Ba).

World-wide movement of fallout particles from nuclear explosions.

Abstract The major peak concentrations of single particles in the ground-level air measured at Fayetteville (94°W, 36°N), Arkansas after the third Chinese nuclear explosion of 9 May, 1966 was explained by the calculated air trajectories. The long range air trajectories at 500 mbar were calculated and a positive correlation was found between the variation of meteorological situations and the daily fluctuations of the particle concentration.

Temporal distributions of radioactivity and89Sr/90Sr ratios during rainstorms

Radionuciide concentrations for 89Sr, 90Sr, 144Ce, and 137Cs were sequentially sampled from two rainstorms to study fallout behavior as a function of rainfall rate and type of storm approximately 7 months after the eighth Chinese nuclear explosion of December 27, 1968. Great time variability in the 89Sr/90Sr ratio was found in conjunction with a well-developed storm on July 21, but a nearly steady ratio was observed in a stratified stable-type storm on August 14. Tapping of stratospheric air appeared to be the cause of the ratio changes. For both storms, a strong trend was found for concentrations of radioisotopes to decrease with increase in rainfall rate. Detailed discussions on meteorological factors, including a dilution effect, are given to interpret the experimental data.

Radioactive Strontium and Barium Fallout

Radiostrontium and radiobarium data in rain obtained in this laboratory indicate that (a) the radioisotopes injected into the troposphere generally travel eastward and circle the earth a number of times before being completely washed out by rain, and (b) the 90Sr inventory in the northern stratosphere appears to have decreased during the past several years at a rate corresponding to the stratospheric mean residence time of 1.1 yr. The paths of the radioisotopes injected into the lower atmosphere were traced by 300 mb and 500 mb air trajectories. During a period of two to three tropospheric mean residence times (60–90 days), the fallout particles seem to circle the earth three to four times. In calculating the stratospheric mean residence time, corrections were applied for the fresh injections of 90Sr into the atmosphere by the Chinese nuclear explosions.

Inter-hemispheric transfer of fresh debris from French nuclear tests in 1968.

NUCLEAR debris particles from the recent Chinese nuclear explosions provided a suitable medium for studying the global atmospheric circulation of airborne material in the northern hemisphere1–3. We have investigated the inter-hemispheric transfer of airborne material by measuring the radioactivities in Japan of short-lived fission products resulting from the recent French nuclear tests in the South Pacific in 1968.

Variation of the Sr89/Sr90ratio in rain caused by the Chinese nuclear explosions of December 28, 1966, and June 17, 1967

Variation of the Sr⁸⁹/Sr⁹⁰ratio in rain caused by the Chinese nuclear explosions of December 28, 1966, and June 17, 1967

Radionuclide fractionation in fallout particles from a land surface burst

The radionuclide fractionation appearing in individual hot particles (highly radioactive fallout particles) from the fifth Chinese nuclear explosion of December 28, 1966, which is believed to have been a land surface burst of several hundred kiloton yield, has been investigated by γ-ray spectrometry. The activities of the ten radionuclides Zr95, Zr97, Mo99, Ru103, I131, Te132, Xe133, Ba140, Ce141, and Np239 were determined, and the initial atom numbers of these nuclides contained in each sample were estimated. The fractionation factors defined with respect to Zr95 were calculated in order to express the degree of fractionation. The results obtained are discussed in relation to the fission-product decay chains and are compared with the results formerly obtained on hot particles from air bursts. It was found that there was considerable difference in radiochemical nature between these hot particles from a surface burst and the hot particles from air bursts. Some assumptions about the mechanism of fractionation in fallout particles are presented, although it now seems difficult to understand the mechanism satisfactorily.

Geochemical Fractionation of Induced Radionuclides in Fresh Nuclear Debris through the Atmosphere—Np-239 and Co-60

Abstract The atmospheric fractionation of induced radionuclides is discussed in some detail on the basis of results obtained by making a radiochemical analysis of fresh nuclear debris originating from recent Chinese nuclear test explosions. Among fresh nuclear debris particles collected at Niigata about 4000km downwind from the Chinese test site, the trend for the enrichment of 239Np was somewhat modified as compared with that derived from an averaged sample collected by a large-scale and high-altitude sampling procedure; more 239Np was present in smaller-size fallout particles. Furthermore, it was found, in rain-water samples collected after the third Chinese nuclear explosion, that the atomic ratio at time-zero of 60Co/95Zr increased with a decrease in the 95Zr-concentration in rain and vice versa. This suggests that the atmospheric fractionation of 60Co-rich particles from 95Zr-rich ones takes place during the travel of atomic clouds around the world.

508. 核爆発による放射性塵の測定および分析

The radioactive airborne debris that reached the sky over Japan in the wake of the 7th Chinese nuclear test explosion of December 24, 1967 were collected with the use of an airborne dust sampler mounted on aircraft and subjected to gross β-activity measurement, γ-ray spectrometry and mass spectrometry. The concentration of radioactive debris in the air stood at about 18, 000pCi/m3 on December 25, from where it decreased gradually to reach a level below 1pCi/m3 on December 28, the level prevalent before the test explosion. Short-lived rodionuclides such as 239Np, 143Ce, 132l and 99Mo were clearly detected by γ-ray spectrometry, but the presence of 237U was not confirmed. The elementary composition of the debris collected shortly after the explosion was not substantially different from those collected at normal times. The content of lithium however, was about 120 times as high as the level before the test explosion. The isotopic abundance ratio of 6Li was 14.6%, about twice the natural isotopic abundance ratio.

The ionization of the air due to beta- and gamma-radiations near the ground. (II).

The results of the measurements of ionization due to the beta and gamma-radiations near the ground surface from 1967 through 1969 are reported, and are discussed comparing with those obtained from 1963 through 1966. The ionization due to the beta-radiation decreased gradually, and the mean value for this period is about I J at one meter above the ground surface, and that by the gamma-radiation (including the cosmic rays) is almost constant, i. e., 5-6 J. In January 1967, sudden increase of the ionization due to the fallout radioactivity caused by the 5th Chinese nuclear explosion test was observed. 137Cs, 90Sr+90Y, 106Ru, and 144Ce were detected from the grass and soil samples taken on the campus of this university in 1964. 144Ce, 140La, 95Zr, 132I, and 132Te were also detected from the fallout particles caused by the 3rd Chinese nuclear explosion test on May 9, 1966.