Is Chornobyl town suitable for living of people with regard to radiological factor?

"Life goes on" Klimakovych Vitaly Born 2002 ( zhytomyr.info ) That's essentially was a key question during the  press ...

"Life goes on"
Klimakovych Vitaly
Born 2002 (zhytomyr.info)
That's essentially was a key question during the press conference organized by Glavcom.ua on August 15, 2012. The information pretext was a request of 35 former Chornobyl town residents to the Prime Minister of Ukraine that certainly echoed in Ukrainian mass media. Among other experts I was invited to the press conference. The format of the press conference did not give an opportunity to present solid scientific arguments, therefore in order to facilitate the discussion of this issue in the spirit of respect for the actual state of affairs and balanced judgment, then after the press conference I decided to add my personal comments, which I was entitled to do due to my qualification level and practical experience (e.g. see below an excerpt from my autobiographical references).

So, as a specialist in radiation protection I'm going to talk about primarily and mainly radiological factors, according to which some time ago zoning of the radioactively contaminated territories of Ukraine was perforemed (see Article 2 of the Laws of Ukraine [1, 2]).

External exposure of the personnel


The main acceptable in the world radiological indicator is the individual dose for a term of 1 calendar year. The main direct data source of individual exposure in the Exclusion Zone including Chornobyl city is data on individual dose monitoring (IDM) of the personnel of enterprises that conduct their activities there. So according to the IDM data register of the Chornobyl Radiioecological Centre (the director of which I had a honor to work in the period 2005-2011) since 2001, the average annual individual dose of external exposure of the personnel (it was from 3 to 7 thousand employees) varied within 0.9 - 1.2 mSv (millisievert).

For example, a long-term trend of individual and collective doses and the number of the personnel in the Exclusion Zone (excluding the Chornobyl NPP personnel, which has its own IDM service that serves its own staff, contractors and visitors) is presented in the graph. The dose value for 2009 in the graph presented excluding data for November and December.


Legend:
  • blue solid - individual dose, mSv/year;
  • red solid - personnel number, thousand;
  • green dashed - collective dose, man·Sv/year;
  • magenta dashed - maximal individual dose, mSv/year;
As it is seen from the graph, there are certainly some cases when the maximum dose of 3 - 10 times higher than the average one. However, one has to understand that we are talking in such cases about occupational exposure, that is received outside the Chornobyl town at workplaces related to radioactive materials with higher levels of activity that are located in the immediate vicinity of the Chornobyl nuclear power plant. Group of personnel exposed to these elevated lebvels is relatively small - a dozen of people, but the maximum dose ever are received by ones. Moreover, even the maximum dose in recent years do not exceed the established regulatory dose limit for professionals, i.e. 20 mSv per year.

Whatever happened, the average dose of irradiation according the IDM characterizes the level of human exposure during their stay (or rather - their dosimeters) in the Exclusion Zone. This time in the majority of cases is very close to the whole year except a vacation period.

But the main interest in the analysis of these data lies in the fact that the measured average annual individual dose of external exposure of personnel is not purely professional dose, and in fact is the sum of three components, namely:
  1. occupational exposure to radiation at hazardous workplaces (can be applied the a small part of the whole personnel);
  2. "Chornobyl background" radiation (i.e. sources of Chornobyl origin in dissipated in the environment) and
  3. natural exposure.
The latter dose component in average over the territory of Ukraine (including the Exclusion Zone) is about 1 mSv/year, i.e. up to the error, it is of the same size as the average annual individual dose of external irradiation of the personnel !

Internal exposure


Exposure to human is defined as internal and external depending on where a source of radiation is located: outside or inside a body (e.g., see IAEA Glossary).

Internal radiation is formed mainly due to intake of radioactivity into a human body through food, including drinking water, and through inhalation of radioactive substances.

It should be admitted that data on internal exposure of the personnel of the Exclusion Zone are absent (according to a mandatory annual reporting form No. 10-RTB-3. The only thing that is systematically done for internal exposure monitoring - annual measurement of 137Cs content in body of workers during their medical examination. However, this method is not suitable for tracking down of inhalation (breathing) intake of radionuclides in such a way that it could be linked to professional activity of a worker. But on the other hand we have the source general hygienic information. So in recent years, about 3/4 of personnel of the Exclusion Zone demonstrated their individual whole body content of 137Cs below the detection capability of a method used, which is about 600 Bq. On the other end every year there are a few individuals showing the excess of reference level of 5,000 Bq per body.

The only group of workers who are provided internal exposure IDM - is a group involved in the project for building a "New Safe Confinement" (NSC or Sarcophagus-2). However, this group is not representative, because it is relatively small and consists mainly of contractors who are hired outside the Zone, work at the site of and are registered by IDM of the Chornobyl NPP. Then they leave the Exclusion Zone after the end of their contracts.

Therefore, it is worthwhile to consider radiological characteristics of factors (according to long-term observations of the Chornobyl Radioecological Centre), forming internal exposure at staying in Chornobyl town, in particular:
  • The average concentration of 137Cs in the air in Chornobyl town is approximately 2·10-5 Bq/m3, and the maximum concentration in short periods of time reaches 2·10-4 Bq/m3.
  • The average concentration of 137Cs and 90Sr in water of Prypyat river in the alignment of Chornobyl town is stable in recent years and is at level of 70 and 150 Bq/m3, respectively (total of dissolved and suspended forms).
  • The average concentration of 137Cs and 90Sr in the water for drinking purpose from groundwater sources in the area of Chornobyl town is about 3 - 4 Bq/m3.

Comparison with permissible levels


In order to assess a degree of risks presented by the aforementioned radiological factors, regulatory limits established for doses and concentrations of radionuclides in various substances that surround a person or that a person uses have to be involved to the analysis. Also levels of nutural exposure to the public should be taken into account. The result of this comparison is as follows:

Radiological indices
of residence in Chornobyl town (minus the professional and natural exposure)
Actual average indicator in Chornobyl town
Dose limit or permissible value for a member of the public
External dose, mSv/year
0.1 (*)
1 (****)
Internal dose, mSv/year
Data not available
137 Cs concentration in air, Bq/m3
2·10-5
0.8
Concentration in water, Bq/m3137Cs
4 (**)
100 000
90Sr
4 (***)
10 000
137Cs content in human body, Bq/kg
10
435 (*****)

Notes:
(*) Direct data are not available. External dose for living in Chornobyl town is assessed as the difference between nominal external IDM data and the level of natural exposure at level of 0.1 mSv/year. Strictly speaking, this estimate is not sufficiently correct: actually the considered value can not be determined using the existing IDM methodology.
(**) The 137Cs concentration in water of Prypyat river - 70 Bq/m3 (this water is not used for drinking).
(***) The 90Sr concentration in water Prнpyat river - 150 Bq/m3 (this water is not used for drinking).
(****) The total of external and internal exposure.
(*****) Constant 137 Cs content of such a value roughly corresponds to 1 mSv/year for peroral pattern intake, using the dose conversion factor from [4].

Transuranium elements (isotopes of plutonium 238, 239, 240 and 241, and 241Am) is not presented in this analysis because the possible exposure to them by several orders of magnitude lower than current exposure from 137Cs and 90Sr.

Summarizing the available factual data one can not state about the discovery of any significant human exposure from sources of the Chornobyl origin precisely for living in Chornobyl town.

Contamination of territory and public exposure in the Exclusion Zone


For radiological assessment of the Exclusion Zone in the first approximation a map of radioactive contamination can be used. The map of 137Cs contamination of the Exclusion Zone as for December 01, 2002 is presented below.



To assess external exposure of a person living at a territory of radioactive contamination the conversion factors from [3, 4] can be used. Taking into account that the external dose of 1 mSv/year corresponds to the contamination density approximately of 1000 kBq/m2 of 137Cs, it can be seen that already in 2002 Chornobyl town was located between isolines 200 and 400 kBq/m2. Of course, by today the situation has been further improved due to natural decay of 137Cs. Today Chornobyl town is located on isoline 0.2 mSv/year of external exposure for condition of permanent residence at this territory of radioactive contamination. Also it is a well known fact that due to human activities cleaning of the urban environment, which is Chornobyl town, is developed much faster than of the natural environment. Therefore, this estimated level of exposure in the town is even lower.

Natural radiation


For an adequate perception of the estimated exposure levels for stays in Chornobyl town attention has to be payed to the current levels of exposure from natural origin. According to UNSCEAR world average annual rates of natural exposure to human look as follows (mSv/year) (see, e.g., here ):

Internal exposure

1.55
External radiation0.87
The total exposure2.42

But in some countries, including Europe (and Ukraine), these levels are much higher. Distribution the total dose (and its components) of natural exposure to most European countries is presented in the figure below (see here).



Territory zoning


In addition the presented map of radioactive contamination gives an idea of ​​the territory parts having a higher priority for returning to normal use. As it can be seen these are the southern part of the Zone, the western part around the railway station Vilcha and north side protruding towards Belarus. It is for these reasons some time ago the State Administration of the Exclusion Zone (now - the State Agency for Exclusion Zone Management) drafted a map of functional diivision of the Exclusion Zone and Zone of Obligatory resettlement (shown below). This map proposed the division of the territory into three areas: industrial (I), buffer (II), and residential (III).



It is advisable to take this map as a basis for future development of the Exclusion Zone.

Prerequisites for transition to recovery phase


The main prerequisite for the early development of the exclusion zone is not even the radiological situation, but the fact that human activity in the Exclusion Zone has never ceased, including:
  • The basis of daily life in the Zone are projects of radioactive waste management, construction Sarcophagus-2 and decommissioning of the Chornobyl NPP (several thousand permanent jobs);
  • Business activity: export of wood and metal, as well as trading activity, etc. are performed on a commercial basis;
  • Squatters (self-settlers) have always lived in the Exclusion Zone;
  • Gradually, new settlers have been "colonizing" Chornobyl ;
  • Annually tens of thousands of visitors let entering the Zone in with the especial peak on Memorial Days (end of April - beginning of May).
The main components of transfer to renewable phase in mitigation of aftermath of the Chornobyl accident are:
  • level of knowledge about the actual level of radioactive contamination of the environment, human exposure formation for living in conditions of radioactive contamination, radiobiological effects of ionizing radiation to humans;
  • knowledge of radiological indices of the Zone, sometimes called radiological situation;
  • availability of legally established criteria for clearance the territory from regulatory control;
  • economic capability and feasibility of such a transition;
  • availability of legal mechanisms to ensure this transition, particularly with using legal mechanisms of the Law of Ukraine "On the zone of ecological emergency" [5];
  • political will and public support.
It can be asserted that today there is no shortage in full any of the above components (except possibly the last one) to start and make the transition to normal life for a significant part of the Exclusion Zone, including Chornobyl town.

Certain changes are observed in the Ukrainian society in relation to the return on the abandoned land. A striking evidence is the cited above appeal of the 35 former inhabitants of Chornobyl to the Premiere.

Also according to media reports in the Parliament do not exclude that evictees will soon return to Chornobyl. In particular, Anatoly Semynoha, the Head of a Parliamentarian Committee for Environmental Policy, Natural Resources and Elimination of Consequences of the Chornobyl Catastrophe said in comments to UNN that return of people to Chornobyl is theoretically possible, but it should solved with each family individually.

Settling the areas


In fact, positive thinking is what realy lacks in addressing many Chornobyl issues. Observations of sociologists and physicians in the post accident years show that many people have developed uncontained (and sometimes pegged) the "Chornobyl victim" syndrome. Moreover, paternalistic preferences are inherent to much of the public. Negative thinking - this is indeed the legacy of Chornobyl, which should be overcome.

For example, if one clarify a question from the title in a way "is it possible or not possible to return back in Chornobyl?", it will be a shining example of negative thinking, which is basically backed by a sense of uncertainty. In contrast, positive thinking makes a start by another dialectical contradiction (as a source of development), e.g.: "Is there a need or there is not a need to come back to Chornobyl?". Thinking in such a way makes logical the next question: "How can it be done?"

There are a lot examples of positive thinking just around us, but the point is to be able to discern them and develop them further. Inter alia one can look at:
Just a few practical steps for the post-Chornobyl recovery and development of Northern Ukraine:
  • Cardinal review of the list of settlements (towards their reduction) from the zones of radioactive contamination outside the Exclusion Zone (this process is already under control of the Cabinet of Ministers of Ukraine).
  • Preparation of a legal act of the completion of the Chornobyl accident and the beginning of the transition to renewable phase (in accordance with the regulatory classification phase radiation accidents).
  • The primarily withdrawal of Chornobyl town from the Exclusion Zone, introduction of "civil" local authorities with further development of towns Vilcha and Polisske.
  • Urgent development and launch of the program for development of abandoned lands of the Zone, released from regulatory control.

Epilogue


My older daughters has been already visited Chornobyl, in adult age. I have a dream to come freely to Chornobyl with my youngest son before he reaches 18 ...

References

  1. Law of Ukraine "On Legal Regime of the territories contaminated by the Chornobyl disaster" dated February 27, 1991 No. 791st-XII ( http://zakon2.rada.gov.ua/laws/show/791% D0% B0-12 )
  2. Law of Ukraine "On the status and social protection of citizens who suffered from the Chornobyl disaster" dated February 28, 1991 No. 796-XII (http://zakon3.rada.gov.ua/laws/show/796-12)
  3. O.O. Bondarenko Exclusion Zone - a factor of radiation risk to the public. SES - preventive medicine, No. 2, 2005, p. 88-95.
  4. Balonov M.I., Barkovskyy A.N., Brook G.J. and others Radiation monitoring of public exposure in laotdalennыy period after the accident at the Chornobyl nuclear power plant. TC project RER/9/074, IAEA, Vienna, Austria, 2007.
  5. Law of Ukraine "On the zone of ecological emergency" dated July 13, 2000 No.1908-III (http://zakon.rada.gov.ua/cgi-bin/laws/main.cgi?nreg=1908-14)

Author


Oleg Bondarenko

Excerpts from autobiography (in the context of this publication):

  • 1980 - graduate of the Physics Department of Kyiv State University. Tarasa Shevchenko, specialty - nuclear physics, qualification - experimental nuclear physics, Kyiv.
  • 2002 - Diploma of Doctor of Biology (specialty radiobiology) for the successful defense of a thesis entitled "Problems of internal dosimetry of human exposure by transuranic radionuclides", Kyiv
  • 2002-2005 - Deputy Director - Head of the radiation safety, State Specialized Scientific Industrial Enterprise "Chornobyl Radioecological Centre", Chornobyl responsibilities: management of the radiation safety in the Chornobyl Exclusion Zone and Zone (compulsory) resettlement.
  • 2005-2011 - Director of the Specialized Scientific Industrial Enterprise "Chornobyl Radiological Center", Chornobyl, responsibilities: implementation of regulations for dose and radiation monitoring of the Chornobyl Exclusion Zone and Zone of Obligatory Resettlement.

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