Integrated Regional Risk Assessments: The case of radioactive contamination on the Kola peninsula. R. Bergman, National Defence Research Institute, Umeå, Sweden; A. Baklanov, Kola Science Centre, Apatiti, Russia; B. Segerståhl, International Institute for Applied System Analysis, Laxenburg, Austria
INTRODUCTION
On the Kola peninsula and in the adjacent parts of the Arctic seas there are several sources contributing to the present radioactive contamination, as well as constituting potential cases of future releases. Nuclear weapons testing, has been performed on and close to the Novaya Zemlya island. A nuclear submarine carrying nuclear weapons sunk 1989 outside the Bear Island. This event, as well as the extensive dumping in the Arctic seas of liquid and solid waste has become an international focus of interest during, the last five years, and the subject of several investigations in situ or in the form of case studies of hypothetical release situations.
Other causes of concern stems from the use of nuclear reactors, primarily on submarines -- in operation as well as on those awaiting decommissioning -- and on icebreakers. The big amount of spent nuclear fuel accumulated from this use, in addition to liquid and solid radioactive waste, are presently in storage on and along the coast of Kola. On the peninsula there is, furthermore, a nuclear power plant with four WER-440 reactors (including two old of type 213).
LEVELS OF RADIOACTIVITY IN THE ENVIRONMENT
In comparing the levels of radioactive contamination commonly
found in the aquatic and terrestrial ecosystems on Kola with
those in most other parts of Europe, it is obvious that the Kola
peninsula at present is very clean. The same conclusion is valid
with regard to the concentrations of radioactive nuclides present
in the adjacent marine environment. At certain sites on land and
in the sea, however, significant contamination has been
recognised -- but mostly confined to local environments -- as a
result of explosions, accidental emission or problems at
radioactive waste depositories.
The principal radiological hazard for the region, as well as
for more distant areas, is consequently the potential
future risk of radioactive pollution from accidents and
mismanagement. To interpret and estimate source-effect
relationships for some of these release conditions it is of
interest to know the current levels, and how the contamination
has responded during the preceding decades to changing inputs,
due to global fallout and mostly waterborne input from other
sources.
The present environmental contamination in the Kola-Barents
region mainly reflects the transfer of radioactive fallout from
the nuclear weapons testing (primarily the atmospheric explosions
at Novaya Zemlya), and from sources outside this region, namely:
SOURCE RELATED DATA AND CASE STUDIES
Much new information about radioactive waste, burial sites and nuclear installations in the Kola-Barents region has recently become attainable through research programs, focused on various radiation issues, which just have been completed or currently are carried out by many Russian and international organisations. The abundant material now accumulated establishes an appropriate basis for -- and also reveals the necessity of -- a comprehensive analysis of radioactive sources and their actual or potential radiological consequences, preferably with observance of completeness, consistency and reliability of this extensive information. In our present study (Baklanov et al. 1996) the available data has been examined from this point of view.
The actual and potential risks, associated with these sources for radioactive contamination and significant radiological consequences, in some cases mainly affects the conditions at local and regional levels, yet in other appear to be far reaching, and of considerable concern for the whole Arctic region, or large parts of Europe. Several case studies for release from the nuclear power plant, from sunken submarines, or from radioactive waste and objects in the sea deals with this issue.
The investigation of levels of radioactive contamination is focused on 90Sr, 137Cs and 239,240Pu, although other radioactive nuclides also are considered. The high availability in important food-chains of 90Sr and 137Cs released into a terrestrial or aquatic environment -- particularly at the northern latitudes of the boreal and arctic areas of the Kola-Barents region -- the relatively high amount of these nuclides already in circulation or present in various storage's, and their radiological importance, indicate that these radionuclides are likely to be of a primary concern. The radiotoxicity of inhaled plutonium and the presence of plutonium isotopes (primarily 239Pu and 240Pu) in nuclear reactors, spent nuclear fuel, nuclear weapons and as a global component of the fallout from nuclear weapons testing, also motivates particular attention.
Sensitivity of the environment
Sensitivity in the general sense considered in this analysis
comprises environmental, as well as demographic characteristics
of the areas that are affected by the prevailing radioactive
contamination, or that potentially may be exposed due to releases
from any of the sources. Ecological sensitivity results from
environmental processes implying relatively high concentrations
or long-time persistence in whole ecosystems, at particular
sites, and in food-chains of key impotence. The demographic
aspects cover the population distribution in relation to the
distribution of release sources, and areas potentially affected
by significant exposure, due primarily to distance from the
source and the extent of food utilisation from contaminated
areas.
RANKNG OF RISKS AND CONSEQUENCES
In order to single out risk cases implying high priority research issues, the main findings from the analysis have first been condensed and arranged in a simple structure allowing, only for a preliminary crude ranking of risks, but identifying those factors that will be subject to closer attention.
Cases definitely known to -- or that with high probability -- belong, to the "high risk" category, may comprise links needed to be more closely analysed in order to yield a satisfactory basis for the assessment process; i.e. priority for research may in such cases be largely based on the demand for better precision or accuracy. Other cases might potentially pertain to the high risk category provided closer examinations would indicate that the necessary physical conditions may be attained for the accident to occur at all , or to become sufficiently severe. These two risk categories establish the basic framework for the classification.
Ranking of consequences - in terms of the radiological significance of a release - is illustrated in table 1 based on two categories of risks: I) those for which release is known to have occurred or for which a significant probability for release has been confidently estimated, and II) those expected to constitute a risk for considerable release provided the outcome of further analysis of certain steps in the event chain (e.g,. for release subsequent to overheating, fire, or critical conditions for spent nuclear fuel under storage).
For consequences connected with a particular release situation the ranking recognises three qualities: H, L and U indicating expected consequences if substantial release occurs - in terms of dose to certain groups* or total populations from external exposure and consumption of food-products derived from the contaminated region. H relatively high radiological consequence; L relatively low radiological consequence; U undetermined consequence ranking has not been done.
* Dose due to external exposure of working personnel, e.g. at decommissioning or submarine operation, is not included.
Further dimensions than considered in this crude ranking are generally needed for a satisfactory analysis of priorities. For instance, the level H comprises some cases leading to relatively high radiological effects mostly in the source region, as well as other cases associated with significant consequences also at long distances from the point of release. Furthermore, the risk may focus on relatively short lasting but intense radioactive release (e.g. a criticality accident in a reactor), or at protracted release to the environment over several years (e.g. stored or dumped radioactive waste).
CONCLUSIONS
The main risk objects in the category "Known or probable risk"
Among the different objects and situations considered in the
category Known or probable risk in table 1, the nuclear
power plant and submarines at refueling are classified as high
risk factors. The sunken submarine Komsomolets, as well as the
radioactive matter dumped in the Barents and Kara Seas in liquid
and solid form, on the other hand, appear to be associated with
relatively low radiological consequences, even if release of all
the presently remaining radioactivity should occur during, a very
short time. Despite the considerable uncertainties still
prevalent in predictions of probable radiological effects for
these cases, the contention is that -- with respect to the large
areas that might suffer from relatively high deposition of
radioactive matter in case of a severe accident, and the
likelihood for such an event -- the Kola nuclear power plant at
Polyarny Zori constitutes the major risk object in this category.
The main risk objects in the category "Potential risk"
Although the specific case of the sunken submarine Komsomolets
is not considered to involve relatively high risk of
environmental contamination now or in the future (NACC 1995), the
known and frequent incidence of other accidents leading to
criticality in reactors on submarines in operation, as well as
during refueling give evidence of the prevalent risk for future
scenarios, possibly in a more serious context with high risk of
exposure of nearby populations, particularly to airborne
releases. This accentuates a general concern for the high number
of submarines present along the coast of Kola.
It is obvious that -- besides the moored submarines still in
operative use -- the accumulation of inactive submarines
containing their spent nuclear fuel, or at different stages of
dismantlement constitutes a potentially serious environmental
hazard.
In addition to the submarines Russia has one decommissioned
nuclear-powered icebreaker, the Lenin, and a decommissioned
service ship, the Lepse. The Bellona report ( Nilsen and Bøhmer
1994) suggests designing a dry dock at a distance from inhabited
areas to store the Lepse, so that the risk of a sinking, is
minimised. Currently, a Russian plan is under discussion
suggesting to tow the Lepse to Novaya Zemlya and bury it there.
No plans seems to exist for dismantling or disposing of the
Lenin.
Due to delays in dealing with the civil and naval
decommissioning issues, there is widespread concern in the Navy
and among city and regional officials in areas where nuclear
shipyards and naval bases are located that these vessels may sink
causing ecological catastrophe. Civilian authorities are also
concerned about accident during defueling and scrapping
operations, as well as about dangers posed by overfilled and
decrepit storage sites or nuclear service ships which are used
for holding solid and liquid radioactive waste.
As evidenced, among other, by the accident in 1986 at the
nuclear fuel storage facility in Zapadnaya Litsa -- which
resulted in a severe contamination problem, and the potential for
a nuclear criticality event (OTA1995) -- very severe accidents
with spent nuclear fuel cannot be excluded. This is also
reflected in some case studies indicating that a fire in a
nuclear spent fuel storage on land or on board a ship, and/or an
accidental chain reaction (a criticality accident) should be
considered. A high priority issue must, therefore, be to analyse
closely the feasibility of such accidents. For those that cannot
be rejected on physical arounds, the further analyses need to
consider whether radioactive release from the spent nuclear fuel
storage in may involve several assemblies or several core
equivalents of fuel -- and in that case under what conditions
release may occur.
References
Baklanov A., Bergman R., Segerståhl B. 1996. Radioactive sources in the Kola region: Actual and potential radiological consequences for man. (submitted).
Nilsen T., Bøhmer N. 1994. Sources to radioactive contamination in Murmansk and Arkhangelsk counties. Bellona report vol 1. The Bellona Foundation.
NACC 1995. Cross-border environmental problems emanating from defence-related installations and activities. Vol 1. Phase 1: 1993-1995. Report no 204. North Atlantic Treaty Organisation.
OTA 1995. Nuclear Wastes in the Arctic. An Analysis of Arctic
and Other Regional Impacts from Soviet Nuclear Contamination.
Washington, Office of technology Assessment. Congress of the
United States.