BRIEFING NOTE

DATE: 21/04/2021

Chernobyl nuclear accident
Status of site facilities Safety - Situation in April 2021

I. Background and general condition of the Chernobyl NPP’s reactors
Thirty-five years ago, on 26 April 1986 at 1.23 a.m. in Ukraine, the Chernobyl NPP’s RBMK Reactor 4 accidentally
exploded during a technical test. The accident led to the complete destruction of Reactor 4, resulting in a firethat could only be extinguished by dumping approximately 17,000 tonnes of various materials into the guttedreactor. The explosion of Reactor 4 in the Chernobyl NPP was classified level 7 on the INES 1 scale. This accident
had serious consequences both on the health of the surrounding populations and on the radiological state of theenvironment.
Reactor 4 was hastily confined in a temporary sarcophagus or object shelter (OS). The uncertainties about thestructural resistance of this OS beyond a period of approximately forty years led the Chernobyl NPP’s operator,
with financial and technical support from the international community, to build the New Safe Confinement (NSC),
an arch-shaped structural shelter, to protect the environment and allow the OS to be decommissioned. Built onan outdoor area away from the reactor, construction work on the NSC began in 2008 and was completed in 2017with its installation over the OS.

The New Safe Confinement over the Chernobyl NPP’s damaged Reactor 4 (source ChNPP: Viktor Kuchynskyi)

RBMK reactors are thermal neutron reactors using graphite as the moderator and boiling light water as the heattransfer fluid. The fuel is U-235 enriched uranium oxide.

1

INES: International Nuclear Event Scale

The other three RBMK Reactors, 1, 2, and 3, built on the Chernobyl NPP site continued to operate until December
2000, when the last reactor in operation, Reactor 3, was permanently shut down. The decommissioning of thesethree reactors is in progress.
The Chernobyl exclusion zone (30 km around Reactor 4) is managed by the State Agency of Ukraine on Exclusionzone management (SAUEZM) on which SSE ChNPP, the Chernobyl NPP operator (State Specialised Enterprise
Chernobyl NPP), in charge of decommissioning the reactors and managing the waste and spent fuel from the site,and CRME (State Specialised Enterprise - Centralised Radioactive Waste Management Company), in charge ofmanaging waste from the exclusion zone around the NPP site, depend.
Given the specific situation of the Chernobyl NPP site, SSE ChNPP’s overall site decommissioning strategy favours
postponed phased decommissioning of all reactors by 2050. This strategy would require the operation of theNSC over Reactor 4 for a hundred years (2017-2117).

II.

Decommissioning strategy for Chernobyl nuclear power plan reactors
Decommissioning strategy for Reactor 4The NSC is 257 m wide, 162 m long, and 109 m high (36,000 tonnes). In July 2020, SSE ChNPP obtained thecommissioning authorisation to ensure the proper operation of its equipment (ventilation, handling cranes). The
next step, which will be very delicate to achieve, will be to dismantle the OS’s unstable structures. This step is
expected to be completed by the end of 2023, and will be followed by a waiting period during which additionalsafety studies on the feasibility and preparation of the recovery of fuel containing material (FCM) will be carriedout. During this period, a final disposal solution for the waste produced by this work will be sought. SSE ChNPP’s
goal is to begin FCM recovery operations by 2050. The operator estimates that these operations, including FCM
processing and packaging for final storage, will take forty years. The target end state calls for thedecommissioning of the NSC once all of the remaining structures of Reactor 4 have been remediated.

(source SSE ChNPP: Viktor Kuchynskyi)2

Decommissioning strategy for Reactors 1, 2, and 3

The decommissioning strategy developed by SSE ChNPP for Reactors 1, 2, and 3 was approved by the Ukrainian
Safety Authority in 2008. The decommissioning stages for Reactors 1,2, and 3 provide for partial
decommissioning (removal of activated guide tubes, reconstruction of reactor roofs, and dismantling of handlingcranes and fuel assembly loading/unloading machines), monitoring for a little less than twenty years, and thendecommissioning the reactors themselves from 2045. The work is expected to be completed in 2064, following
the clean-up of the three reactors’ civil engineering structures.

(source SSE ChNPP: Viktor Kuchynskyi)2Final state of the Chernobyl NPP

Given the uncertainties regarding the decommissioning of Reactor 4, subsequent industrial use of the site ispreferred.

III.

Management of spent fuel from the Chernobyl NPP

Central storage pool: ISF-1

During the operation of the reactors from 1977 to 2000, the Chernobyl NPP used 21,284 fuelassemblies. Since the end of 2016, all these fuel assemblies have been stored in a central storage pool (ISF-1).
Pool ISF-1 was commissioned in 1986. This facility is not designed for the long-term storage of spent fuel, and its
operation is planned until 2028. All spent fuel assemblies will then be transferred to a new dry storage facility(ISF-2).
Dry storage: ISF-2
ISF-2 was designed with a service life of a hundred years and consists of two parts; a facility for processing spent
fuel assemblies and a storage area made up of horizontal concrete storage modules. The facility is designed witha processing capacity of 2,500 fuel assemblies per year. On 18 November 2020, during live testing of the ISF-2
facility, the first package loaded with spent fuel assemblies was inserted into one of the concrete modules in thefacility's storage area. The active phase of hot testing ended on 14 December 2020. The authorisation to operate
ISF-2 is expected to be issued by the Ukrainian Security Authority in April 2021.

Source: SNRIU website - The first drum containing spent nuclear fuel being placed in the ‘dry’ spent nuclear fuel storage facility – ISF-232https://inis.iaea.org/collection/NCLCollectionStore/_Public/48/047/48047388.pdf

3The first drum containing spent nuclear fuel being placed in the ‘dry’ spent nuclear fuel storage facility – ISF-2 (dazv.gov.ua)

IV. Management of waste produced by activities on the Chernobyl NPP site
There are two types of waste produced by activities on the Chernobyl NPP site:

waste produced by the normal operation of site facilities;
waste from the 1986 accident, including waste from the OS.

The Chernobyl NPP’s operator estimates that there will be around 177,255 m 3 of radioactive waste from thedecommissioning operations on the four reactors. Liquid radioactive waste is estimated at 36,148 m3 and solid
waste, at 141,107 m34. Currently, 22,645 m3 of solid and liquid waste are stored on the site, the majority of which
is liquid waste (20,133 m3) requiring subsequent treatment (Cf. LRTP below).
Treatment of solid and liquid waste produced on siteoSolid waste management: an Industrial Complex for Solid Radioactive Waste Management (ICSRM) was built
between 2001 and 2009 to treat all solid waste from the Chernobyl site. This facility was designed to treat
3,500 m3 of solid waste per year. After processing and storage on site, the waste packages produced will betransferred to the surface storage facility located on the Buryakovka site, in the Chernobyl exclusion zone.
The ICSRM is made up of various sub-assemblies (sorting, processing, storage), all of which should becommissioned in 2021, for thirty years.

oLiquid Waste Management: liquid radioactive waste will be treated by a cementation process at the Liquid
Radioactive waste Treatment Plant (LRTP) and encapsulated in 200-litre steel drums. This facility is designed
to treat 2,500 m3 of liquid waste per year. The 200-litre drums are packed in fours in a reinforced concrete
container which is then stored before being transferred to a surface storage facility located on the Vector
industrial site. The LRTP was commissioned in 2014 and, to date, has only treated 3.4 m 3 of liquid waste
generating forty packages of solid waste.

Interim and final storage of radioactive waste produced by the Chernobyl NPP
The storage facilities on the NPP site are expected to be saturated within two to three years. A storage facility is
being built in Reactor 1’s engine room to temporarily store 16,000 m3 of waste packaged in 200-litre drums (3,200packages).

4 https://chnpp.gov.ua/en/activity/radioactive-material-management/radioactive-waste-management