Transfer Factors for Nuclear Emergency Preparedness

Nordisk kernesikkerhedsforskning Norrænar kjamoryggisrannséknir Pohjoismainen ydinturvallisuustutkimus Nord isk kjernesikkerhetsforskning Nordisk kårnsåkerhetsforskning Nordic nuclear safety research DK0300006 NKS-78 ISBN 87-7893-134-7 Transfer Factors for Nuclear Emergency Preparedness Eila Kostiainen, Riitta Hånninen Radiation and Nuclear Safety Authority (STUK), Finland Klas Rosen, Enok Haak, Åke Eriksson Swedish University of Agricultural Science Sven Poul Nielsen, Miranda Keith-Roach Risø National Laboratory, Denmark Brit Salbu Agricultural University of Norway . .34/15 December 2002 Abstract This report by the NKS/BOK-1.4 project subgroup describes transfer factors for radiocaesium and radiostrontium for the fallout year and the years after the fallout. The intention has been to collect information on tools to assess the order of magnitude of radioactive contamination of agricultural products in an emergency situation in Nordic environment. The report describes transfer paths from fallout to plant, from soil to plant and to animal products. The transfer factors of radionuclides (Sr, Cs, I) given in the report are intended to be used for making rough estimates of the contamination of agricultural products soon after the heaviness and composition of the deposition (Bq m ) is known. Key words Transfer factor; Agriculture; Emergency Preparedness; Sr; Cs; I; NKS-78 ISBN 87-7893-134-7 Pitney Bowes Management Services Denmark A/S, 2003 The report can be obtained from NKS Secretariat P.O. Box 30 DK - 4000 Roskilde, Denmark Phone +45 4677 4045 Fax +45 4677 4046 www.nks.org e-mail [email protected] Transfer Factors for Nuclear Emergency Preparedness Report from the NKS/BOK-1.4 project group Countermeasures in Agriculture and Forestry Eila Kostiainen * Riitta Hanninen * Klas Rosen" Enok Haak" Åke Eriksson' Sven Poul Nielsen * Miranda Keith-Roach * Brit Salbu" * Radiation and Nuclear Safety Authority (STUK), Finland # Swedish University of Agricultural Science, Sweden + Risø National Laboratory, Denmark B Agricultural University of Norway Preface Within the NKS/BOK-1.4 project countermeasures in agriculture and forestry a survey of environmental transfer factors to be used in emergency preparedness planning was carried out. The survey covered the existing Nordic data on transfer factors in agricultural environment. This report is the result of the survey, participants of collecting the data were: Denmark: Sven Poul Nielsen, Miranda Keith-Roach , Risø National Laboratory Finland: Eila Kostiainen, Riitta Hanninen, Radiation and Nuclear Safety Authority (STUK) Norway: Brit Salbu, Agricultural University of Norway Sweden: Klas Rosen, Enok Haak and Ake Eriksson, Swedish University of Agricultural Science The conclusions and recommendations issued in this report are solely the responsibility of the authors and not of NKS. Present address: Dept. of Environmental Sciences, University of Plymouth Contents Summary 5 1 Background and introduction 5 2 Methods 5 3 Transfer paths 6 3.1 Transfer fallout-to-plant 6 3.1.1 Retention by grass crops 7 3.1.2 Retention by grain crops 10 3.2 Transfer soil-to-plant 13 3.3 Transfer to animal products 14 4 UNSCEAR report data 15 SNRPBdata 17 6 Discussion 20 7 References 21 Appendix 1: Transfer factors 22 Appendix 2: Bibliographic database 23 Summary The project was to find tools to assess the order of magnitude of radioactive contamination of agricultural products in an emergency situation. Making a literature survey of transfer factors did this. The review was mainly Nordic data, but to some extent also international data of environmental calculation models. The database of publications including transfer data was collected country-wise. Transfer factors for radiocaesium and radiostrontium are given in this report, for the fallout year and for the years after the fallout. They are intended to be used for making rough estimates of the contamination of agricultural products soon after the heaviness and composition of the deposition (Bq m"2) is known. They are aimed to give a basis for making decisions on the need of measurements for monitoring feedstuffs and for taking relevant countermeasures in agriculture to decrease radionuclide transfer to food items. 1 Background and introduction In the connection of the late-phase nuclear emergency exercise Huginn (Lauritzen, 2001) the assessment of radionuclide concentrations was found difficult especially for the fallout year, because transfer data was not easily to be found for the fallout occurring during the growing season. The most reliable assessments of the radionuclide concentrations pertained to the year fol- lowing the fallout year. There was a need for a survey of transfer factors especially for the fallout year (growing season). The transfer factors for plant root uptake of 137Cs and 90Sr are generally available for the first year after the fallout year, and this data can be used also for assessments, if the fallout happens in spring before the growing season. This data concerns the root uptake of plants, but data con- cerning the transfer from the leaves to edible parts of the plant is scarce. For plants which are planted before deposition early in spring, only some contamination on the above ground parts would be expected, but little or no activity in the roots, because caesium is known to migrate very slowly in soil. Caesium is not expected to reach the depth of the roots before the fields have been ploughed and tilled and therefore considerable transfer from soil to plant through the roots cannot be expected before next year. 2 Methods A review of literature was made by participating countries during the project work, concentrat- ing in the data from Nordic countries published in literature and in-house reports. Both experi- mental data, and data related to real conditions (after Chernobyl) were looked through. The ex- perimental data was the only data found for assessing the transfer of radionuclides when deposition takes place during the growing season. The transfer data after the Chernobyl accident for the next years was available for Nordic countries to be used for the years after the fallout year. The data included in environmental calculation models was gone over. Also the international literature was reviewed using databases of INIS, Springer-Verlag, Elsevier and Academic Press. The database of publications including data of transfer factors was made as an Excel table with columns: Author/source, Publication name, Site, Deposition, Product(s), Soil, season, Transfer factor/foodchain transfer models. The data was compiled according to the author and publishing year (Appendix 2). 3 Transfer paths In fallout situation the human population can be exposed to external and internal radiation by different pathways, Figure 1. We consider here the internal radiation from intake of food products, due to transfer of radionuclides to crops and animals in agriculture. As generally found, the transfer to a certain crop will be much less if fallout takes place between two growth seasons than during a growth season. The direct transfer from fallout to a crop exposed to the atmosphere during a growth season will always be much higher than the indirect transfer from a contami- nated ground surface, which in turn will be higher than the transfer by root uptake from a con- taminated soil or plough layer. AtfciOSPH£R£ WET /» DEPOSITION t i RV.LOFF RD07 Figure 1. Main pathways for radionuclides to man (Rosen, 1996). Different measures and units are used to evaluate and compare the transfer of radionuclides from one sector to another sector within the nutrient chains of ecosystems. Aspects on use of some of them will be treated below in the order: transfer from fallout-to-plant; transfer from soil-to- plant; transfer from feedingstuff-to-animal products. Some of the most used transfer factors/ ratios/coefficients are defined in Appendix 1. 3.1 Transfer fallout-to-plant To describe the direct interception and retention of fallout radionuclides by agricultural crops, two types of measures, TRd-value, and FRd-value, can be used. The TRd-value, is obtained when the activity of a radionuclide transferred to 1 kg dry weight of the crop is weighted by the deposition, d, per square meter at the time of fallout: Concentration in plant (Bq (kg d.w.) ) TRd = (D Deposition on ground (Bq m"-2)\ where d = deposition. The calculated value of TRd is proportional to the contamination level of the growing crop and independent of the fallout level at the moment of deposition. It is a yield independent measure, easy to compare fore different field situations. If the yield per unit area is determined, the amount of a nuclide intercepted and retained by a crop per unit area can be weighted by the amount deposited through this unit area. The result of this operation is the Fraction of the deposition Retained by the crop. This fraction, denoted FRd, can be found by multiplying TRd by the crop weight per unit area: FRd = Yield*TRd = m2(kg d.w.)"1 * (kg d.w.) m'2 (2) The FRd-value is a yield dependent measure, which can be expressed as the fraction or percent of initial fallout. The fraction recovered by the growing crop, FRd, is dimensionless and influ- enced by the same factors as TRd. The time of year and growth stage when radioactive fallout takes place greatly determine the nuclide transfer to an agricultural crop. After initial interception of the fallout and up to harvest, there is a period of time dependent falloff, which reduces the nuclide content in the crop. By repeated sampling during that part of the season the changes in the crop can be observed and half-times calculated, both with regard to the nuclide content per unit dry weight or TRd, and with regard to reduction in nuclide recovery or FRd. 3.1.1 Retention by grass crops Grass fields, pastures or leys, are dynamic systems, used for feeding cattle.

Load more