SPERA Newsletter

February 2003

Primary objective: SPERA is a strictly apolitical, scientific organisation. Its primary objective is to encourage and facilitate communication among scientists working in the South Pacific region in the field of environmental radioactivity, which involves the study of the occurrence, behaviour and impact of radioactive species present in the environment due either to natural processes or resulting from human activities.

Biannual Newsletter of the South Pacific Environmental Radioactivity Association

Editor

Paul Martin

Environmental Research Institute of the Supervising Scientist

GPO Box 461

Darwin NT 0801

Australia

Fax: +61 8 89201195

E-mail: Paul.Martin@ea.gov.au

Committee

President: John Twining, ANSTO, Sydney, Australia

jrt@nucleus.ansto.gov.au

Vice President: Sandor Mulsow, IAEA-MEL, Monaco

S.Mulsow@iaea.org

Secretary: Riitta Pilviö, NRL, Christchurch, New Zealand

rick_tinker@nrl.moh.govt.nz

Treasurer: Sue Brown, ANSTO, Sydney, Australia

sab@ansto.gov.au

Oceania representative:

Sitaram Garimella, USP, Fiji

garimella_s@usp.ac.fj

Membership Enquiries

Please send enquiries to the Secretary at the above address.

Quote

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny ...'

Asimov, Isaac (1920-1992)

From the President

I would like to preface my first message with a big ‘Thank you’ to out-going President (and current editor) Paul Martin. He is to be congratulated on his excellent leadership of SPERA over the preceding years during which time SPERA’s profile was raised substantially, particularly outside the region. It is my hope that we can all make SPERA more widely known and active, especially within the region. However, to achieve that goal will require each of us to take any opportunity to promote the association as they arrive. I appreciate your assistance in this matter. For my part, I also plan to make more formal approaches to institutions across the region to make them more aware of SPERA and to seek membership and participation by interested researchers within those laboratories.

To enhance our profile and to promote our major objectives I would like to progress Paul’s idea to encourage students to undertake studies in the South Pacific region using environmental radioactivity. If any of you have suggestions on how this might be achieved I would be pleased to hear from you. Better yet, send them to the editor! As an example, ANSTO are currently involved in setting up a Post-Graduate Certificate Course on Applications of Environmental Radioactivity, with the University of NSW. There will be more on this later in the newsletter.

At the time of writing we are still finishing up the work on SPERA 2002. There were some difficulties arising in relation to publication of the proceedings. However, Paul Martin, Ross Jeffree and I have since been in contact with Steve Sheppard, the new Editor in Chief at the Journal of Environmental Radioactivity, and it looks like we are back on track. More details will be provided as they come to hand. In relation to the conference itself I would like to thank all of my committee for helping to make the occasion a general success. Without naming everyone I would particularly like to mention Gillian Peck’s efforts in keeping the show on track. Thanks Gillian!

We are all now looking forward to our next conference in Valdivia, Chile, 2004. I encourage all members, especially those in the western Pacific, to start the ball rolling to ensure that as many delegates as possible can attend what will be the best SPERA conference yet, both scientifically - and socially!

John Twining

SPERA President

News from the Regions

Environmental Research Institute of the Supervising Scientist (eriss), Northern Territory, Australia - contributed by Andreas Bollhöfer, Andreas.Bollhoefer@ea.gov.au

In 2002 ERISS will be moving to a new laboratory in Darwin. Designing he labs has been keeping us very busy for some time, however we re now finally at the stage where concrete will soon be poured. One of our main considerations has been how to ensure that the concrete used for the flooring of the detector room (and the adjacent rooms) has the lowest possible concentrations of gamma emitting radionuclides, in order to minimise our background count rates.

We have faced this problem twice previously in the pouring of concrete laboratory flooring at our present laboratories in Jabiru East. Our approach has been to test possible sources of sand, gravel and cement and require that the contractors use those materials selected by us. The following are some results from our testing, showing concentrations in the materials we accepted and rejected in 1987, and some results for the materials available this year:

*alternative materials available, but rejected

These results demonstrate the importance of testing building materials prior to laboratory construction. Note especially the dramatic differences in K-40 content of the sands. Choice of the wrong materials could result in the necessity of adding several extra centimeters of lead shielding to a gamma detection system.

In this type of situation, speed in the analysis is crucial. Quick answers are needed in order to provide feedback so that, if all the materials chosen are unacceptable, then a search for new materials can be undertaken. Also, a few days before the pour we test the actual piles of aggregate and sand which will be used, in order to check that the builders have the correct materials. From our experience, it is also important to actually be on the site on the day of the pour, to check that the correct piles are sourced. Out of interest, we also take samples of the concrete itself.

Rather than use our standard techniques, we simply place the sample in a large plastic marinelli beaker and count on a HPGe detector system. We do not worry about radon retention etc. Mainly we are interested in the relative concentrations in different materials, and so high accuracy is not required provided precision in the results is reasonable. If the K-40 concentrations are an order of magnitude different between two sand samples, you don't need to know the answer to an accuracy of a few percent in order to make your choice!! Samples of the final materials used are prepared for more accurate analysis later, but this is mainly out of interest.

Australian Nuclear Science and Technology Organisation (ANSTO), Sydney, Australia – contributed by Peter Airey, pla@ansto.gov.au

Nuclear Education at ANSTO: a New Initiative

Recognising the need to maintain and extend those nuclear capabilities which underpin national development activities, the IAEA recently convened a Meeting of Senior Officials on Managing Nuclear Knowledge¹ (Vienna, 17 to 19 June 2002). The six major recommendations were concerned with the organisation and dissemination of nuclear knowledge through institutions working cooperatively.

The needs articulated by the IAEA reflect the situation in many countries. ANSTO has traditionally responded to the challenge through internal staff development programs. In a new initiative, the Environment Division is joining with the Department of Civil and Environmental Engineering within the University of New South Wales in the development of two topics within the University’s Graduate Certificate program. The topics are: Isotope Techniques: Applications to Industry and the Environment and Radioactivity: Environmental Monitoring and Remediation.

The Isotope Techniques course will cover basic nuclear, radiation and health physics that underpin a range of case studies. These include: the applications of nucleonic gauges to industry and coastal engineering; the application of tracer techniques to studying the fate and behaviour of contaminants in surface waters and sediments; and the applications of environmental isotopes to hydrology, sedimentology and aspects of oceanography. In the Radioactivity course, case studies illustrating environmental monitoring and remediation will be selected from the mining industry (probably uranium mining); from problems associated with technologically enhanced naturally occurring radioactive materials; and from nuclear activities (the Maralinga clean-up, the operations of a nuclear facility, and environmental aspects of safeguards).

Each course will be offered in a ‘short course’ mode and will be available to students in Australia and abroad. Further information can be obtained from Dr Peter Airey (E-mail: pla@ansto.gov.au or Dr William Peirson W.Peirson@unsw.edu.au ).

Marshall Islands Dose Assessments and Radioecology Program, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA - contributed by Terry Hamilton hamilton18@llnl.gov

Consequences of the US Nuclear Testing Program in the Marshall Islands

Bikini and Enewetak Atolls in the Northern Marshall Islands were used in the 1950s by the United States for testing nuclear weapons. The most significant event in the entire US Pacific test campaign was the CASTLE–BRAVO shot on 1 March 1954 that produced widespread radioactive fallout contamination over much of the northern Marshall Islands (Figure 1), and lead to accidental exposure of Marshallese people, US servicemen and a group of Japanese fishermen. Displayed communities on Bikini, Enewetak and Rongelap Atolls continue to struggle between the societal fear of radiation, and desire to resettle their native homelands. Under the auspices of the U.S. Department of Energy, the Health and Ecological Assessment Division at Lawrence Livermore plays a key role in providing measurement data and dose assessments to characterize current radiological conditions on affected islands, and minimize exposures of resettled and resettling populations.

Figure 1. Map of the Marshall Islands, showing the location of the Bikini Atoll and the fallout pattern from the CASTLE-BRAVO shot of 1954.

Cesium-137 Transfer from Soils into Plants

Marshall Island coral soils make cesium-137 much more available for plant uptake than do soils of North America and Europe. For example, soil-to-plant cesium-137 transfer factors (becquerel per kilogram dry weight plant / becquerel per kilogram dry weight soil) for tropical fruits on Bikini Island range between 2 and 40. This compares with values between 0.005 and 0.5 for vegetation growing in temperate zones (IAEA 1994).

This very significant difference occurs because coral soils are composed almost entirely of calcium–magnesium–strontium carbonate with varying amounts of organic matter, essentially little or no aliminosilicate material, and very low concentrations of potassium. Enhanced plant uptake of cesium-137 from coral soils can be attributed to both the absence of clay mineral binding sites and the low concentration of potassium in the soil. Knowledge of preferential uptake of cesium-137 into local food crops was a major factor in (1) reliably predicting the dose for returning residents, and (2) developing a strategy to limit the availability and uptake of cesium-137 into those crops.

Dose Assessments

Doses are estimated for all exposure pathways using radionuclide data for cesium-137, strontium-90, plutonium-239 and -240, and americium-241 in locally grown foods, a diet model for pertinent local food consumption, external gamma exposure calculations, and exposure via inhalation from radionuclide resuspension. We estimate that the ingestion pathway will contribute 70-90% of the dose to island residents, mostly through uptake of cesium-137 into terrestrial foods such as coconut, Pandanus, breadfruit, and papaya. External gamma exposure from cesium-137 accounts for about 10-30% of the dose. Plutonium-239 and -240 and americium-241 are major contributors to the dose via inhalation, but this pathway contributes only about 1% of the total.

The estimated maximum annual effective dose due to weapons testing for current Bikini Island living conditions is about 4 millisieverts per year when imported foods are made available. The natural background dose in the Marshall Islands is about 2.4 millisieverts per year, of which a significant fraction comes from consumption of fresh fish. The estimated background dose plus the bomb-related dose totals ~6.4 millisieverts, which exceeds the average background doses of 3 millisieverts per year in the U.S. and 2.4 millisieverts per year in Europe.

Guidelines for controlling prospective dose to the general public (from nuclear power plants, for example) are not relevant to situations where people want to resettle in areas contaminated by nuclear weapons fallout. General guidance provided by the International Commission on Radiological Protection and the International Atomic Energy Agency recognizes that below an effective annual dose of 10 millisieverts, the situation should be reviewed, and if a cost-effective, socially acceptable, and environmentally sound remediation strategy can be implemented to reduce the dose, it should be considered. Our goal is to develop cost-effective measures to reduce the dose associated with resettlement at the atolls.

Remedial Measures to Reduce Doses

An effective method to reduce the island radionuclide inventory is to remove the organic-rich layer of soil that extends to about 40 cm depth; much of the cesium-137 is retained within this layer. This material, derived largely from litter from surrounding vegetation, supplies nutrients for plant growth and controls the water-retention and cation-exchange capacity of soil. Consequently, its removal leads to severe environmental impacts that require very-long-term commitments to rebuild the soil and revegetate the island.

We have evaluated several other measures to eliminate cesium-137 from the soil and/or reduce its uptake into food crops. The most effective, and the easiest to implement, is the application of potassium to the atoll soils. A dramatic reduction in cesium-137 uptake occurs in tropical fruits after a single application of potassium-rich fertilizer to selected experimental plots on Bikini Island (Figure 2). This treatment reduces the associated ingestion dose to about 5% of pretreatment levels. This option avoids soil removal, and the added potassium increases plant productivity.

Figure 2. Effect of potassium treatment on the concentration of cesium-137 in coconut meat. The availability of potassium ions, an essential nutrient for plants, blocks the uptake of cesium-137 into the fruits, giving the people resettling contaminated atolls an alternative to excavation of the topsoil and destruction of existing plantings of coconuts and other food crops. Our “combined option” recommends removel of soil in housing and village areas where people spend most of their time, in order to reduce the external dose, and treatment of the rest of the island with potassium fertilizer.

Moreover, rainfall transports cesium-137 (and potassium) out of the root zone of plants into the groundwater. In the longer term this will lead to a reduction in cesium-137 levels in local food crops and reduce the current dose estimates even further. We are now focusing on determining the duration of the effects of potassium treatment on cesium-137 uptake into plants, and the rate of environmental loss of cesium-137 in the atoll ecosystem.

Acknowledgment

This work was performed under the auspices of the U.S. Department of Energy, the University of California at the Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

References

International Atomic Energy Agency (1994), Handbook of Parameter Values for the Prediction of Radionuclides Transfer in Temperate Environments, IAEA, Vienna, Technical Reports Series No. 364, p. 74.

Robison, W. L., K. T. Bogen, and C. L. Conrado (1997), “An Updated Dose Assessment for Resettlement Options at Bikini Atoll—A U.S. Nuclear Test Site,” Health Physics 73(1), 100–114.

Robison, W. L., W. A. Phillips, and C. S. Colsher (1977), Dose Assessment at Bikini Atoll, Lawrence Livermore National Laboratory, Livermore, CA, UCRL-51879, Pt. 5.

SPERA2002 Proceedings

A serious problem with the publication of the SPERA2002 proceedings arose last year when the online journal TheScientificWorld closed due to financial difficulties.

The SPERA committee had email discussions with Steve Sheppard, the editor of a print journal (JER: Journal of Environmental Radioactivity) and he has agreed that the proceedings can be placed in that journal after a full refereeing and editorial process.

Unfortunately, Ross Jeffree has reluctantly had to withdraw from the position of editor, as he has been placed in charge of a major project at Ansto and would not be able to devote the necessary time to the editing work. After some dicussions I agreed to take on the role as guest editor for the journal.

I am anxious that the editing work proceed at a reasonable pace, especially given the time which has passed since the conference. However, there will be some difficulties due to the history to date.

Ross has provided me with referees' reports for a number of papers, however given the difficulties which occurred with TheScientificWorld at its closure, a certain amount of history (e.g. possibly some referee reports) will have been lost. Therefore, I am asking that anyone who may have provided a referee report to TheScientificWorld for any SPERA2002 papers please email me letting me know of this fact. Ideal would be the provision of an electronic version of that referee report.

The difficulties experienced up to this time are unfortunate, however the opportunity for the proceedings to be published in this major international journal is a positive for SPERA and for the proceedings authors.

Paul Martin

Newsletter Editor

Paul.Martin@ea.gov.au

Next Newsletter

The newsletter can only be as successful as you make it, by providing material for publication.

The following types of articles are particularly welcome:

• any information of interest to SPERA members

• news about yourself or your organisation

• advice about techniques, equipment, etc.

• advertisements for forthcoming events

• descriptions of projects

• requests for assistance, advice, co-operation

• questions

• abstracts of publications

• book/paper reviews

• anecdotes, cartoons, pictures

A reminder for articles will be e-mailed to all members, so please ensure that your e-mail has been made available to SPERA. If you have not received an e-mail regarding this issue of the SPERA newsletter it means that you are not on the emailing list!