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New - Orleans, June 3-3, 1984 POTENTIAL RADIATION DOSES TO PEOPLE LIVING NEAR PLUTONIUM CONTAMINATED AREAS IN PALOMARES JUNTA DE ENERGIA NUCLEAR - SPAIN
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POTENTIAL RADIATION DOSES TO PEOPLE LIVING NEAR PLUTONIUM CONTAMINATED AREAS IN PALOMARES. JUNTA DE ENERGIA NUCLEAR, SPAIN On January 17, 1966, there was an aviation accident vertically above the town of Palomares (Cuevas de Almanzora) in Spain. As a consequence of this accident, four thermonuclear bombs carried by one of the planes fell, and due to the impact on hitting the ground, the nuclear fuel in two of them ignited,This gave.rise t the formation of an aerosol, which , in varying degrees of magni tude, contaminated approximately a 226-hectare area correspon ding to underbrush , farmland and urban areas. The contaminated region and full extent of the areas correspon ding to the different levels of alpha ray contamination resulting and measured in the period inmediately following the accident can be observed in Figure 1. The points where the impact of the two thermonuclear devices, which due to the numbering assigned them, corresponded to bombs 2 and 3, respectively, ocurred on the groun are indicated in Figure 1. The'other two were recovered intact, one in the dry bed of the Almanzora River near its mouth and the other one in the sea. The contaminated vegetation and surface layer of soil (appro ximately 10 cm deep), where the total surface alpha contamination values were greater thaji 1.17 x 10 Bq x 100 cm , were colie ted , separated and disposed of as radioactive wastes. The rest of the contaminated area devoted to agriculture was irrigated - thoroughly , plowed to a depth of approximately 30 cm,and was subjected to a light homogenization to reduce the concentration of radionuclides contaminating the surface of the soil and to di lute them in a significant volume of soil to get concentration levels considered sufficiently safe, so that there would not -
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be any unacceptable existing plutonium i sotopes inha 1 ation risks from resuspension for people living in this area or farming the From the moment the decontamination operations in the area - were finished by removing the wastes and restoring the farmland, a research program was begun. For the purpose of maintaining a constant reference for the various studies on air, vegetation, soil and persons planned for the Palomares area, the area contaminated during the acci dent has been subdivided into three zones. These zones corres pond respectively to the two which were greatly influenced by - contamination arising from each of the thermonuclear bombs that broke up and partially ignited and to the urban zone in which ninety percent of the population lives. The two zones correspon ding to the points of impact have been called 2 and 3 , in accor dance with the numbering order of the bombs that impact on them; the zone containing the urban area has been labelled 5. In figu re 1, the relative location of each one of these zones and their boundaries can be observed. The experimental program on the contamination of breathable air in the area was planned for the following purposes: - measurement of existing Pu concentrations in the air of some zones of the area. - determination of the inhalation risk for people living and far ming in the area, and as a consequence, the internal radiation risk for those who live and work there all or most of their lives - practical deduction about whether the decontamination and resto ration actions in the area were correct , and consequently , .whether the theoretical reasoning used to estimate the future - residual contamination risk was adequate. In this report the following matters are shown and diseased: - average annual Pu air concentrations during the 15-year period corresponding to 1966-1980.
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- cumulative dose equivalents to various tissues during the periods 1966-19 30 and 1966-201 5 for dwellers a®C groups who have continually been inhaling the ’ Pu ave rage annual air concentration during the fifteen-year period - committed dose^^u1 ents for various tissues due to the inhalation of ’ Pu average annual air concentration as an aerosol of'l (AMAD) by the standard man during the fif We believe that these values can show a first estimation of the incidence that the existing plutonium resuspension in the soil will have on the population living and farming that area. 2.- SAMPLING , ANALYTICAL AND CALCULATION PROCEDURES. Throughout the area four sampling stations were set up-two in zone 2, since it is the most extensive and has greater topo graphical variation, and one in zone 5, which corresponds to the town , and another in zone 3. In Figure 1, the location of each one is shown. The number and location of the air sampling stations was selec ted by taken into account the size of the contaminated area, its topographical characteristics and the irregular dwelling distri The characteristics of the area surrounding each of the four sampling stations are the followings: This station is located in the little valley whose boundaries are the hills around the point of impact of bomb No.2. The soil of the^ ■ close surrounding area is rocky and hardly has any brush or other wild plants. Due to these characteristics, plowing it was not po ssible. The station was located in the center of an area in which the surface contamination levels originating froij} the accident va ried, at tha£ time, from 1.17 x 10 Bq x 100 cm to 1.17 x IQ3
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It was located on a parcel of land devoted to farming and near a group of inhabited dwellings. In this parcel and ^ts environs, surface contagjination levels were between 1.17 x 10 Bq x 100 cm mination levels were produced in the surrounding land that was cultivated, perhaps due to its topographical characteristics. This station is located in the town and is considered represen tative of the air breathed by people living in the urban center. The surface contamination in the parcel in ^hich it is located and those around it was less than 1.17 x 10 Bq x 100 cm This station is located in the center of a strip of cultivated land, which ,. if the surrounding land near the point of impact is excepted, would hav£ the greatest contamination from the im pact of bomb No.3. It is located in a flat area where the land is cultivated, and it is five meters below the level at which the impact occurred. Surface alpha contamination of parcels near th| sampling station reached values between 1.17 x 10 Bq x 100 cm and 1.17 x 10 In station 2-2 and P, samples have been taken every day of the year throughout the period 1966-1980; and in stations 2-1 and 3-1, every day during the period from July 1966 to October 1969. The aerosol sample corresponds to an average air volume on the order of 90 m , and the sampling time is 24 continuous hours. The analyses were performed on compound samples, correspon ding to a period of ten days, for each of the sampling stations. This means that the spectrometric measurement of each of the com pound sample^ corresponds to a breathable air volume on the or The radioanalysis technique used to determine the concentratic
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of all the ’ Pu in the aerosol samples from each of the sam pling stations is that which, with slight modifications, has been developed and used in Los Alamos National Laboratory (U.S.A.) This technique essentially includes plutonium dissolution using nitric acid, its separation by ionic exchange, electroplating on stainless steel disk and alpha spectrometric measurement of its activity. 2.3.- Estimation of cumulative dose equivalents. To estimate the cumulative dose equivalents to varios tissues for people of different ages a model has beer developed; the mo del is based on some specific parameters (1,2)and the standard I.C.R.P. dosimetric parameters proposed by the ICRP Task Group o:1 1,,ng Dynamics (3' and the later considerations made by ICRP The model is valid for a number of radionuclides (NUC) equal to or less than 20, whose concentration remain constant during each of the various variable time intervals (NIC) which occur consecu tively throughout a considerable period of time. The hipotheses established for the model are the following: - A constant concentration of the radionuclide in air exist during a certain time i nt er va 1 j, - The inhalation rate, R^(m x s ), changes for some age groups during a fraction of the time Fu. in relation with the inhalation time interval due to the fact that the standard age of a person can change during the period. reaches the organ k and is exponentially eliminated from this or gan by means of a effective half life. - The number of atoms of the radionuclide n existing in the or gan k at the beginning of the interval i is equal to the number of atoms of the radionuclide n existing in the organ k at the end of - The mass organ is variable with the time interval, since the person can go from one age classification to another during the
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The FORTRAN V codification of this model has been named DOSIN The DOSIN Program has been applied to the Pu inhalation by three population groups. Each group represent people who have been children and youths, youths and adults and adults during the period 1966-1980, that is to say people who were age 1,11 or 18 in 1966. We think they are representative of the whole population group with regag{jgt£4Jhe number of years that dwellers have been exposed to the ’ Pu inhalation risk in each one of the stan dard ages during the period 1966-1980. Bearing in mind that we do not possess a exact knowledge of the particle size in the plutonium aerosol captured at each sam pling station we have done the calculation for five different AMADS. The AMADs considered have been 0.3, 0.5, 1,2 and 5 jim . The results of Pu concentration in samples taken at the air sampling stations and the dose equivalents assess to various tissues in the hipothesis of continuous exposure to inhalation of the average annual concentrations by the three groups of dwe llers are discussed below. a),- In the ten-days samples taken along the years in the £^r240 sampling stations the frequency of the existence of ’ Pl particles ^n concentration exceeding the detection limit (1.9 x 10 Bq x m ) during the period 1966-1980 are shown »* From the discussion of values set forth in Table 1 it can be deduced that : “Plutonium dioxide particles are resuspended in the air due to meteorological factors, agricultural labor and movement of the earth. The presence of such particles has been established in sam ples taken at the four stations.
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- The frequency of the existence of plutonium particles in sam ples corresponding to each one of the ten-day periods has been varying as a function of time for each one of the sampling sta The sampling station location with regard to residual con tamination is clearly shown in the results obtained , since the percentage of concentrations greater than the detection limit - during the period 1966-1969 was 37.0 in the zone of the town , while at station 2-2, it was 60.0 ; values corresponding to these percentages at stations 2-1 and 3-2 were 42.7 and 49.1 respecti For samples taken in stations 2-2 and P during the period 1966-1980 , the percentage with values greater than the detec tion limit was 33 at station 2-2, while at station P, it was At station 2-2 l4o^e max^mum values for the sampling percentage with a ’ Pu content in excess of the detec tions limit occurred in 1967, with values of 81.8 and 74,3 23gA^4gtati°n 2-2, minimum percentages of samples having a * Pu content in excess of the detection limit occurred in 1973 and 1976, with a value of 8.3 in both cases. As of 1977, an increase in these values began and reached a value of 51.4% by 1 ' §' 2I03 means as 1977, the resuspension of exis ting * Pu in the soil of zone 2 increased, as it had grea ter direct incidence at station 2-2. The resuspension increase is, as can be proven , related to transformation operations on farmlands located in parts of zone 2, which either had not been cultivated since the accident or never had been cultivated, due to hills covered with poor-quality wild vegetation. ^^s^f 196 8 , the number of samples at station P with a Pu content greater than the detection limit diminished 1 *c ons i d e rab 1 y , so that between 19 6 9 and 19 76 , percentages of samples with a content exceeding the detection limit were - between 2.8 and 0. As of 1977, and in the case of station 2-2 an increase in these percentages occurred , reaching a value of 34.3 in 1980, which we think without a doubt was due to earth movement and transformations produced in the Palomares area, and especially in zones 2 and 5 , in order to convert uncultivable land into cultivatable land and to build greenhouses.
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b).- Average annual concentrations of Pu have been asse ssed through the results of the analysis made in all tendays samples taken every year in e|^ station. The values for the average annual ’ Pu air concentra tion during the fifteen-year period 1966-1980 for stations 2-2 and P are those shown in Table 2. Average annual con centrations for stations 2-1 and 3-1 during the period 1966-1969 are also shown. From the air concentration values shown in Table 2 we can arrive to the following. - Most of the average annual concentration of ’ Pu in the air has been less than a tenth of the Derived Air Concentration (DAC) of Class Y plutonium compounds for the public at all the sampling stations and in each and every year of the period studied for each one of them. The exceptions corresponds to air sampling station 2-2 (1967 and 1969) and air sampling station 2-1 (1969). - At station P, wl^pse values are representative of the exposure of the Palomares dwellers, m ax imum__ average annual concentration was in 1966, 1.5 x 10 Bq x ra , ' and then a decline occurred, which for the period 1968 to 1976 remained more or less constant. As of 1977, the annual concentration of activity increased, and in 1980, it rgached thg maximum value for the entire period, 2.8 x 10 Bq x m .This increase was, as previous ly indicated, related to earth movement following the transformation of part of the hilly zone with residual surface contamination corresponding to zone 2 and tracts of uncultivated land corresponding to zone 5 into culti - At station 2-2, whose values are representative of the dou ble influence of working contaminated land and of the …
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