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avril 2020

April 15, 2020

Information note

Fires in Ukraine in the exclusion zone around the Chernobyl power plant:
Point position

Since the publication of our previous information note on April 7, 2020, fires in Ukraine have spreadnearby the Chernobyl nuclear power plant. Following numerous questions received by our Instituteabout their radiological consequences, which, according to Ukrainian authorities, which have now beenbrought under control, this note provides an assessment of the possible radiological impacts for thefirefighters as well as for the inhabitants of Kiev. It also reviews cesium 137 (137Cs) airborne activity levels
likely to be detected in France due to the transport of contaminated air masses.

1/ Current situation as of April 15, 2020
Forest fires broke out in Ukraine about ten days ago in a territory heavily contaminated by the 1986
Chernobyl nuclear accident. These fires reached the exclusion zone and the surrounding environment(about 1 km) of the nuclear power plant from April 8, 2020 (see Fig. 1).
Nearly 400 fire-fighters and 90 specialized aerial and terrestrial vehicles, including planes and waterbomber helicopters, have been mobilized for more than a week for the control of the fires. According tosome estimates, the burned area reached about 20,000 ha.
Ukrainian authorities said earlier this week that "the efforts of the fire- fighters and the rain have
reduced the forest fire in the Chernobyl exclusion zone". They assured Tuesday, April 14, 2020 in themorning that the risks of fire spreading were now limited to isolated or smoldering fires.
At the end of April 14, 2020, the Ukrainian authorities indicated that the fires were under control. The
satellite images of April 15, 2020 show no more fire spot in this part of heavily contaminated territories(see Figure 1).

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Figure 1: Daily maps of fire spots between April 3 and April 15, 2020 (source of data: NASA / FIRMS).
Location of the Chernobyl nuclear power plant is marked with a red star and the arc of a red
circle delimits the exclusion zone with a radius of 30 km around the plant.

2/ Available measurements
Ambient gamma dose rate measurements near fire-affected areas are available at
http://www.srp.ecocentre.kiev.ua/MEDO-PS/index.php?lang=ENG. They do not reveal abnormal values.
It should be remembered that these measurement devices are only capable of detecting major
radiological accidents1. Such a probe is installed at the French Embassy in Kiev and is part of the IRSN's
Téléray network deployed in France.
The radioactivity released into the atmosphere by the fires was therefore not high enough to bedetected by these devices.
On the other hand, much more sensitive measurements have been carried out by various Ukrainianscientific bodies which have published airborne 137Cs activities from aerosol samplings2 (see Table 1).

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Gamma radiation resulting from radioactivity in air greater than 1 Bq/m3
Airborne particulate matter2

Table 1: Measurements of Airborne cesium 137 activity in Kiev and in the Chernobyl exclusion zone
reported by two Ukrainian scientific bodies.
Central Geophyscial Observatory, Kiev
Sampling period

05-06
April

137
AirborneCs
83
activity (µBq/m3)

06-07
April

07-08
April

08-09
April

09-10
April

10-11
April

11-12
April

12April< 110<140290<140700170<18006-08April

08-09
April

09-10April

65

220470

Ukrainian Hydrometeorological Institute, Kiev
Sampling period

27 March 27 March 06-07-5 April-6 AprilApril

137
AirborneCs50
activity (µBq/m3)

5657

Measurements in the exclusion zone3
LocationDate
ASKRS Chernobyl
10 April 2020
ASKRS Kids
08 April 2020
ASKRS Kopachi
11 April 2020
ASKRS Kopachi
08 April 2020
ASKRS GRP-750
08 April 2020
Chernobyl, vul. Kirov, 42
11 April 2020
Chernobyl, Vul. school, 612 April 2020
Korohods'kyi Peninsula 12 kv
12 April 2020
Korogodske L-in 41 m2
12 April 2020
Chernobyl NPP Ukrenergomontazh - GRP13 April 2020
750

Airborne 137Cs activity (µBq/m3)
240541000
72630
2600
290
42000
1600
180000In Kiev, the highest airborne 137Cs activities in the air were recorded from April 9 to 11, 2020: 470 micro
becquerel/cubic meter (µBq/m3) from April 9 to 10 ; 700 µBq/m3 from April 10 to 11. A value of 1,200µBq/m3 during the night of April 4 to 5, 2020 has also been reported by the Scientific State and TechnicalCenter for Nuclear and Radiological Safety in Ukraine but has not been confirmed.

3

Ukrainian Government Agency for the management of exclusion zones: http://dazv.gov.ua/novini-ta-media/vsinovyny/radiatsijna-situatsiya-v-zoni-vidchuzhennya-v-rajoni-pozhezhi- stanom-na-12-3.html

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These values are significantly higher than the values usually measured for cesium 137 in the air in Kiev
4and show evidence of the passage of contaminated air masses. However, they remain moderate andhave no health consequences (see Chapter 4).
In the Chernobyl exclusion zone, much greater air contamination is observed due to the closeness to themeasuring devices in the burned area. The possible consequences of this contamination are assessed inChapter 4.

3/ Modelization
IRSN has performed a modeling estimation of the amount of radioactivity re-emitted by fires. This would
be around 200 GBq 5 issued between April 3, 2020 at 12:00 p.m. and April 13, 2020 at 12:00 p.m.
The simulations carried out show a good agreement between measurements provided by the Ukrainians
and modeling results.
On this basis, IRSN simulations indicate that air masses from the area of the fires that occurred on April 5and 6 were able to reach France in the evening of April 7, 2020. As of April 14, these air masses still
covered half of the territory (see Figure 2). Expected radioactivity levels in France are extremely low,
below 1 µBq/m3 in 137Cs.
The releases occurring between April 9 and April 11, 2020 are more significant according to themodeling. The weather conditions that prevailed until April 14 favored the transport of air masses toBelarus, southern Ukraine, eastern Romania and Bulgaria. They have not reached France to date.
Aerosol sampling on filters by large-volume devices from the IRSN’s OPERA-AIR network and associatedlow-level measurements are underway. This search for traces requires the implementation of very
precise and long measurements, the results will not be available until the end of next week.

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5About 6 µBq/m3 of 137Cs
1 GBq = 109 Bq = 1,000,000,000 Becquerels

4Figure 2: Modeling of the plume dispersion over Europe. Red triangles represent the fire locations of thefires and the blue dots the measurement stations in Ukraine). A video is also available on theIRSN web site6.

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https://www.irsn.fr/EN/newsroom/News/Pages/20200415_Fires-in-Ukraine-in-the-Exclusion-Zone-aroundchernobyl.aspx

54 / Dosimetric impact
IRSN has carried out an estimation of the dosimetric impact of the fires according to different scenarios:- For a fire-fighter who worked for 100 hours in the exclusion zone in an environment with an airborne
activity level of 1 Bq/m3 (or 1,000,000 µBq/m3) of cesium 137 and 1 Bq/m3 of strontium 90 (a major
assumption compared to the measurements carried out in the area), the calculated dose corresponding
to the inhalation of radioactive fire smokes is approximately 13 micro sievert (µSv) 7.
It should be noted that this dose is much lower than that which results from the external exposure offire-fighters by the radiation emitted by the contaminated soil and which, in the exclusion zone, is very
often greater than 1 µSv/h. This is consistent with estimates made by Ukrainian scientists which indicatethat the doses received by fire-fighters as a result of smoke inhalation are in the range of 1% of the dose
induced from the exposure to ground radiation8.
- for a resident of Kiev exposed for a few days to radioactivity levels comparable to those measured by
Ukrainian organizations in Kiev, the inhalation dose received by an adult is less than 1 nano sievert (1 nSv= 0.001 µSv) which is extremely weak9.
- IRSN completed its assessment by considering the exposure due to the ingestion of contaminatedfoodstuffs in Ukraine, near the disaster areas, by the deposit of radioactive ashes transported in the fireplume. The evaluation was made by assuming the consumption of 500 grammes of leafy vegetables(most penalizing case) per day for a two-month period10. The effective dose committed for an adultwould reach, after two months of consumption, 30 µSv for strontium 90 (90Sr) and 15 µSv for 137Cs. This
exposure remains low.
As mentioned in the IRSN note of April 7, 2020, the impact resulting from the inhalation of theradioactivity carried by the masses in the air arriving in France should be insignificant.

5 / Risk for storage facilities
The last reactor at the Chernobyl plant was shut down in 2000 (20 years ago), but there are still
radioactive materials on site. These are first of all the structures and debris from unit 4 which exploded
in 1986, the removal of which poses significant technical difficulties, and waste from the cleanup anddismantling of the reactors and the site, on which they are located. The spent fuel from the other threereactors (1 to 3) is stored on site, in a dedicated facility (ISF2). This is a dry storage.

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11 µSv for 90Sr and 1.4 µSv for 137Cs. 1 µSv = 0.001 mSv
V. A. Kashparov, S. M. Lundin, A. M. Kadygrib, V. P. Protsak, S. E. Levtchuk, V. I. Yoschenko, V. A. Kashpur, N. M.
Talerko. Forest fires in the territory contaminated as a result of the Chernobyl accident: radioactive aerosol
resuspension and exposure of fire-fighters. Journal of Environmental Radioactivity, 51, (2000), 281-298.
9The annual public exposure limit is 1,000 µSv as an added effective dose.
10Doses by ingestion of contaminated food induced by airborne activities of 1 Bq/m 3 of 137Cs and 1 Bq/m3 of 90Sr for
24 hours. In this season, only vegetables, milk and meat can be produced. For this estimate, IRSN retained the casepenalizing leafy vegetables with a consumption of 500 grams / day. Considering a dry deposit with a deposition
velocity of 5 10-3 m/s, the deposited activity is then 430 Bq/m2.
86Very significant efforts have been made by the Ukrainians and the international community to ensurethat these radioactive materials are stored securely in new installations designed and built in accordancewith current safety standards. This is the case for the on-site waste storage facilities and the newsarcophagus which now protects the damaged unit. The risks of accidents were taken into account in thesafety studies which were produced to support their design. Particularly endowed with a robust civilengineering, the risk that these installations could release the radioactivity which they contain due tofires is unlikely.
There are also storage facilities and waste deposits in the exclusion zone, which are located in areas
which were a priori affected by the fires. Table 2 summarizes the main characteristics of these deposits
and the map in Figure 3 specifies their location.
Table 2: Main waste storage and warehousing facilities in the Chernobyl exclusion zone
Facilities

Characteristics

Waste Types

Buriakovkastorage

Trench storage still in use

Poldesny storage

Storageincasemates

Storage of so- Storage
called phase III buildings
waste from theChernobyl nuclearsite(« ChNPP
stage III »)Waste
repositories(« RICS »)inLow andwaste levels

inintermediate 2.6 1015 Bq(Cs, Sr, Eu, Pu, Am)

concrete Sanitation waste following 2.6 1015 Bq
the accident (high-level and 137( Cs, 90Sr, 134Cs, 154Eu,
long-lived waste)
155
Eu, 238Pu, 239,240Pu, 241Pu,241Am)
concrete Sanitation waste produced 3.4 1014 Bq
during the emergency 137
Cs, 90Sr, 155Eu,phase (low and medium (239,240Pu, 241Pu, 241Am
activities and long life)

Open ground trenches and Low andwells)
waste levels

Storageof Storage
Vektor's
buildings
radioactive waste

Inventories

238Pu,intermediate 2 1015 Bq au total(spread over 9 sites)

concrete Low-level solid waste from 1.7 1011 Bq
theChernobylpower 90 137 134 135 235( Sr, Cs, Cs, Cs, U,
station and other sites
236
U, 238U, 237Np, 241Pu,241Am, 242Am)

Storage of used Long-term storage
sealedsources radioactive sourcesfrom Vektor

1.6 1013 Bqof

1,634 sources of Cs, Co,Am, Ra7

Figure 3: Map of waste storage and warehousing facilities in the exclusion zone.

These facilities are mostly old and some of them were created in an emergency to meet the needs toreduce the consequences of the accident in the exclusion zone. Generally sketchy in design, however,they have characteristics that offer good resistance to the remobilization of waste activity by fires. Thus,
the Buriakovka site consists of trenches covered with a compact layer of clay material. It is also cleared(see Figure 4). The storage facilities at Podlesny (see Figure 5) and at phase III of the Chernobyl nuclear
site are made of concrete and are also located in cleared areas. The more recently commissioned Vektor
storage and warehousing facility is intended to store mostly essential waste.

Figure 4: View of the Buriakovka storage site

Figure 5: View of the Podlesny storage site

The most basic sites are the trench waste deposits distributed in the exclusion zone (RICS: Raw InterimConfinement Sites) and whose main radioactive inventory is mainly grouped in 9 zones located near thepower plant. These are trenches containing waste produced in the exclusion zone, including metal parts,
rubble and contaminated wood.
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Even if, strictly speaking, they do not have barriers against the long-term dissemination of activity in theenvironment, these sites remain not very vulnerable with regard to the risk of fire because the waste isburied and covered with a layer of soil or sand.
In conclusion, even if there is a very significant activity in the exclusion zone linked to waste deposits, itappears to be not very mobilizable by fire. In fact, there is no measure in the exclusion zone published todate which suggests that a storage or warehousing site has been reached and may have released asignificant part of the radioactivity it contains.

IRSN will continue to monitor the radiological situation in Ukraine in the coming days and will publish theresults of air radioactivity measurements it will perform on the aerosol filters of its OPERA-AIR network
in France.

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