SPERA Newsletter

March 2002

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

Rick Tinker

National Radiation Laboratory

PO Box 25-099

Christchurch

New Zealand

Fax: +64 3 366 1156

E-mail: rtinker@nrl.moh.govt.nz

Committee

President: Paul Martin, ERISS, Northern Territory, Australia

paulm@eriss.erin.gov.au

Vice President: John Twining, ANSTO, Sydney, Australia

jrt@nucleus.ansto.gov.au

Secretary: Rick Tinker, NRL, Christchurch, New Zealand

rick_tinker@nrl.moh.govt.nz

Treasurer: Sue Brown, ANSTO, Sydney, Australia

sab@ansto.gov.au

Membership Enquiries

Please send enquiries to the Secretary at the above address or via

the email shown below or via the web-site (under construction).

spera@nrl.moh.govt.nz

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)

Editorial

After four great years of living in New Zealand and employment at the

National Radiation Laboratory (NRL) as Team Leader of the

Environmental Laboratory, I have decided to uproot and move on. I

have accepted an offer to join the Environmental Team at the

Australian Radiation Protection and Nuclear Safety Agency

(ARPANSA) Melbourne office. Among other duties, my main

responsibly will be the development, implementation and operation of

a metrics facility capable of measuring ultra low levels of radionuclides

that may result from clandestine nuclear weapon detonations.

In departing NRL, I believe it to be necessary to resign my position of

SPERA secretary. Among other reasons, the SPERA constitution

requires that the SPERA Committee be comprised of at least one

member from Australia, New Zealand and French Polynesia. So I

urge those from the South Pacific who would like to become more

involved in their association to consider nomination for the SPERA

committee at the next election at the General Meeting to be held

during the SPERA 2002 conference. On a personal note, the highlight

of this position was the role I played as acting president during the

SPERA 2002 New Caledonia conference.

Another SPERA duty I have taken on has been that of the SPERA

newsletter editor. Newsletters have been published biannually with

many contributions from regions around the South Pacific and around

the world. Although I would like to continue my role as SPERA

newsletter editor, it probably needs new blood to generate fresh

enthusiasm and a new look. For this reason I would recommend that

a new editor be found at the May General Meeting. So again, if you

are interested, put your hand up. I would like to personally thank the

continued support from a small main stay of contributors and I hope,

with their continued support, others are encouraged to provide articles

for the next SPERA newsletter, who ever the editor may be!

For myself I have enjoyed my involvement with SPERA and I am

certain it will continue well into the future.

Rick Tinker

SPERA Secretary and Newsletter Editor

In September I represented SPERA as a keynote speaker at the 26th

annual conference of the Australasian Radiation Protection Society

(ARPS). The theme of the conference was "Radiation Safety -

Measurements Matter" (Somehow I have the feeling that Riaz Akber

and Ross Kleinschmidt were involved in this choice of theme).

I talked about gamma and alpha spectrometry with a particular

emphasis on applications in the mining and milling industry. Many

thanks to those SPERA members who supplied me with information

and graphics so that I could give the audience an overall picture of the

measurement facilities which are available in the region and the

various approaches people are taking to problems.

SPERA2002 is fast approaching, and by the end of November all

abstracts should hopefully be submitted. You can keep yourself up to

date on developments from the website

(http://www.ansto.gov.au/spera2002/).

And don't forget to consider putting your hand up for organizing

SPERA2004 - if you are interested, your committee you love to hear

from you.

On a personal note, our Secretary Rick Tinker will be getting married

in May of next year in Aviano, a small Italian village north of Venice.

Rick is busy brushing up on his Italian so he'll know when he has to

say "I do". I am sure I am speaking on behalf of all SPERA members

in wishing Rick and Sylvia all the best for their future together.

Paul Martin

SPERA President

Environmental Research Institute of the Supervising Scientists

(ERISS), Northern Territory, Australia - contributed by Paul

Martin, paulm@eriss.erin.gov.au

Environmental Research Institute of the Supervising Scientist

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.

University of Salzburg, Inst. Of Physics and Biophysics, Vienna,

Austria – contributed by Peter Bossew, p.bossew@magnet.at

and Peter Hofer, peter.hofer@irf.univie.ac.at, Institute of Risk

Research, University of Vienna, Austria

Hot Particles in Soil from the Chernobyl exclusion zone

This year‘s research excursion to Chernobyl (Sept. 2001) was

focused on the search for hot particles in soil and the small scale

horizontal variabilities of the radioactive inventory and the depth

distribution parameters. Our investigation area is a meadow located

near the abondoned village of Kopachi ca. 6 km south of the NPP.

The 137Cs inventory of the site is between 1 and 3 MBq/m²; from

meteorolocigal records of the time of the accident (26 April 1986) it is

known that the deposition is entirely due to dry fallout. In an early

survey it has been estimated that in this region around 75% of the

initial fallout was particulate, mainly consisting of small fuel fragments,

as opposed to the mainly condensed fallout in Central and Western

Europe.

Furthermore it is known that the particles are subject to a relatively

fast and efficient erosion in soil due to acidic components of the soil

solution and to microbial activity. Therefore, after a few years after

fallout a major part of the radioactivity contained in the particle is

available for convective-diffusive transport with the soil solution. In fact

the soil activity profiles measured 15 years after fallout look very much

the same as the ones known from Western Europe, i. e. typically

convective-diffusive shaped.

The task is now to screen actual soil columns for hot particles, in

order to identify single particles; measure their activities; calculate the

fraction of the total activity contained in particles; and investigate the

depth distribution of both particles and sorbable components.

Screening soil samples is a cumbersome and time consuming job. It

is done with a small window beta monitor which is being moved above

a thin layer of dry soil spread out on a sheet of paper (see picture).

In order to keep the background low the layer must be kept as thin as

possible. Particles with a minimum 137Cs activity of 1-2 Bq can be

detected this way. The regions of the sample with higher count rates

are then separated, spread on another sheet, again screened, an so

on, until one (mostly unvisible) particle has been identified, which is

then fixed with ordinary adhesive tape.

Some preliminary results out of the investigation of a few samples are:

• Around 10% of the total 137Cs activity of the soil column is

contained in hot particles (> 1 Bq) out of the initial > 75%,

which is in accordance with literature (Bar‘yakhtar et al.,

1998); in single soil layers (each 1.5 cm thick, 18 cm² cross

section) the fraction can be more than 50%. Per soil layer (27

cm³) up to 10 particles (> 1 Bq) have been found.

• The particles are mainly composed of 137,134Cs, 90Sr, 241Am,

154,155Eu, 239,240Pu; however no detailed alpha and beta

spectrometry have been performed so far. The maximum

137Cs activity found so far is 90 Bq.

• There are basically two groups of particles: one with a

154Eu/137Cs ratio around 0.75%, the second having ca. 3% (up

to >10%). Few particles consist almost only of Cs, one has

been found with 60Co, apparently a fragment of activated

structural material. The ratio 239/240Pu : 154Eu is around 3:1,

quite constant for all particles (Pu is calculated out of the

easily measurable 241Am, based on the known initial ratios

241Pu : 239,240Pu, thus avoiding radiochemical Pu analysis).

The Eu,Pu/Cs ratios are dependent of the temperature of the

reactor at the time when they were emitted: particles from the

first explosion (the reactivity excursion) have more Cs, as

opposed to particles expelled in later stages, when the reactor

had heated up, which are depleted in the more volatile (and

therefore emitted in gaseous form) caesium.

• Unexpectedly, there is a considerable mobility of particles in

soil. Some particles have been found in a depth of 10 cm

below surface; the profiles appeared undisturbed by human or

animal intrusion, however, as can be conclued from the shape

of the activity profiles. Therefore a considerable downward

transport of particles (probably by percolation with rainwater)

can be anticipated.

• The size of the particles can be estimated from their 154Eu

activity (replacing 144Ce which is traditionally used for this

purpose (Wagenpfeil & Tschiersch 2001), but which has

decayed below detectibility since 1986). Typical diameters

calculated this way are between 9 and 25 μm, which can be

confirmed by visual inspection with an ordinary light

microscope, in which the particles appear as irregularly

shaped black corns. (X-ray fluorescence electron microscopy

is planned.) Fig. 1 shows the frequency distribution of the

particle sizes; one can see that the contribution of small

particles (< 10 μm corresponding to the approx. detection

limit) is probably small.

Fig.1: cumulative particle size distribution: approximately lognormal,

GM = 15.4 μm, GSD = 1.43

These Chernobyl research activities are organized as a cooperation

between the universities of Vienna and Salzburg with the European

Centre of Technogenic Safety (TESEC), Kiev, Ukraine. The latter

provides the infrastructural support (lot of burocracy is involved when

working in the exclusion zone and when taking out samples, which is

heavily restricted by Ukrainian law, which is now being enforced, by

the way), laboratory facilities, site knowledge, research ideas,

accommodation etc. The cooperation is open to everybody, so those

interested in participating can contact us or TESEC (head Dr. Victor

Poyarkov, urtc@mipk.kiev.ua). Costs must be borne by the

participants, however.

The TESEC also organizes workshops for students or people involved

with radiation protection. Last september a group of students from

Vienna and Salzburg attended a course about monitoring procedures

in radiological emergencies, personel and equipment protection etc.

(with field exercises in the exclusion zone, thus simulating quasiserious

conditions). A similar course is planned for 2002.

References

Bar‘yakhtar V. et al. (1998): Comprehensive risk assessment of the

consequences of the Chornobyl accident. Report, Science and

Technology Center in Ukraine & Ukrainian Radiation Training Centre,

project No. 369, Kyiv 1998.

Wagenpfeil F. & J. Tschiersch (2001): Resuspension of coarse fuel

hot particles in the Chernobyl area. J. Environ. Radioactivity 52, 5-16

For a review of properties, formation etc. of hot particles see Sandalls,

Segal & Victorova (1993): Hot Partcles from Chernobyl: A review, J.

Environ. Radioactivity 18, 5-22.

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.

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.

The National Radiation Laboratory (NRL) in Christchurch, New

Zealand, is seeking an analytical chemist (preferably with

radiochemistry experience) to work in its environmental radioactivity

laboratory.

NRL is a specialist business unit of the Ministry of Health and is the

nationally recognised authority on the safety aspects of exposure to

ionising and non-ionising radiation. For radioactivity measurements,

the NRL maintains a specialised environmental radiochemistry

laboratory dedicated to low-level radioactivity measurements,

providing a range of services to many clients.

The primary requirements for this intermediate position are

qualifications and experience as an analytical chemist (desirably in

radiochemistry). The candidate will work as a team member in the

Environmental radioactivity laboratory with an emphasis on

measurement of radioactivity in a variety of sample matrices (air,

water, soils, slurries, and foodstuffs). Experience with quality systems

and the application and maintenance of instrumentation would be of

advantage. A detailed job description and person specification can be

found on our website: www.nrl.moh.govt.nz.

Please submit a C.V. with your letter of application to arrive by 30

April 2002 to:

The Manager,

National Radiation Laboratory

PO Box 25-099,

Christchurch

New Zealand

Email: jim_turnbull@nrl.moh.govt.nz

For additional information, please contact Dr Riitta Pilviö at

Riitta_pilvio@nrl.moh.govt.nz or on (+64) 3 366 5059.

The NRL has a commitment to the Treaty of Waitangi and has an

Equal Employment Opportunities Policy

The Lord of the Rings: an allegory of the PhD?

For anyone who has written, is writing, or is considering a masters or

PhD - be assured that it's all part of an ancient quest!

The story starts with Frodo: a young hobbit, quite bright, a bit

dissatisfied with what he's learnt so far and with his mates back home

who just want to get jobs and settle down and drink beer. He's also

very much in awe of his tutor and mentor, the very senior professor

Gandalf, so when Gandalf suggests he take on a short project for him

(carrying the Ring to Rivendell), he agrees. Frodo very quickly

encounters the shadowy forces of fear and despair which will haunt

the rest of his journey and leave permanent scars on his psyche, but

he also makes some useful friends. In particular, he spends an

evening down at the pub with Aragorn, who has been wandering the

world for many years as Gandalf's postdoc and becomes Frodo's

adviser when Gandalf isn't around.

After Frodo has completed his first project, Gandalf (along with head

of department Elrond) proposes that the work should be extended. He

assembles a large research group, including visiting students Gimli

and Legolas, the foreign postdoc Boromir,and several of Frodo's own

friends from his undergraduate days. Frodo agrees to tackle this

larger project, though he has mixed feelings about it. ("'I will take the

Ring', he said, 'although I do not know why.'")

Very rapidly, things go wrong. First, Gandalf disappears and has no

more interaction with Frodo until everything is over. (Frodo assumes

his supervisor is dead: in fact, he's simply found a more interesting

topic and is working on that instead.) At his first international

conference in Lorien, Frodo is cross-examined terrifyingly by Galadriel

and betrayed by Boromir, who is anxious to take the credit for the

work himself. Frodo cuts himself off from the rest of his team: from

now on, he will only discuss his work with Sam, an old friend who

doesn't really understand what it's all about, but in any case is

prepared to give Frodo credit for being rather cleverer than he is.

Then he sets out towards Mordor.

The last and darkest period of Frodo's journey clearly represents the

writing-up stage, as he struggles towards Mount Doom (submission),

finding his burden growing heavier and heavier yet more and more a

part of himself; more and more terrified of failure; plagued by the

figure of Gollum, the student who carried the Ring before him but

never wrote up and still hangs around as a burnt-out, jealous shadow;

talking less and less even to Sam. When he submits the Ring to the

fire, it is in desperate confusion rather than with confidence, and for a

while the world seems empty.

Eventually it is over: the Ring is gone, everyone congratulates him,

and for a few days he can convince himself that his troubles are over.

But there is one more obstacle to overcome: months later, back in the

Shire, he must confront the external examiner Saruman, an old enemy

of Gandalf, who seeks to humiliate and destroy his rival's protege.

With the help of his friends and colleagues, Frodo passes through this

ordeal, but discovers at the end that victory has no value left for him.

While his friends return to settling down and finding jobs and starting

families, Frodo remains in limbo; finally, along with Gandalf, Elrond

and many others, he joins the brain drain across the Western ocean

to the new land beyond.

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!