One of the most common mistakes of Chornobyl NPP guests including journalists is to name the spent nuclear fuel storage facilities (ISFs) as “nuclear repositories”. To put in order the definitions we’ll try to tell about all – former and future – storage facilities of Exclusion Zone and how they are different from one another.

Exclusion Zone “Storage facilities” can be nominally classified into 4 types as follows:

— spent nuclear fuel storage facilities;
— radioactive waste and material storage facilities;
— radioactive waste disposal sites;
— sites for temporary localization of RAW including the termini for contaminated vehicles.

SNF storage facilities

Nuclear fuel for RBMK is uranium pellets packed inside the fuel elements (FEs). A FE couple in a special container makes a fuel assembly (FA). A little more than one thousand six hundred of exactly these FAs plunged into the reactor core (RBMK) generate power. After uranium burn-up the “tired” fuel assemblies are pulled from the reactor and for cooling and activity level reduction are transferred to special spent fuel pools where they are kept for some years. And then the time comes for the spent nuclear fuel (it is exactly the name for FAs after all mentioned procedures) to get to a spent fuel storage facility (ISF).

Very important aspect! SNF is not radioactive waste. Radioactive, yes, it’s true; waste, no! It’s false! Why?

Neither of the currently existing reactors can ensure full burn-up of the fuel. It means that there is a possibility, for example, to carry out a number of not simple process operations with the fuel elements, to separate them from the accumulated fission products, to enrich them again with ²³⁵U isotope and to include them repeatedly into a fuel cycle. Unfortunately, at present, the cost of spent fuel reprocessing and the cost of fresh fuel extraction are about the same but the technologies are being improved, and waiting for the time when SNF can be reused efficiently the spent FAs “sleep” in storage facilities. And they are placed there with observance of all radiation and nuclear safety standards not having any adverse impact on the environment.

So, spent nuclear fuel is a valuable source of raw material for the technologies of future and ISF is the groundwork for long-time prospects. There is no sense in disposal of something that can be used later.

ISF-1

There are two ISFs at Chornobyl NPP.  

In the interim spent nuclear fuel storage facility of wet type (ISF-1), which was built yet while the USSR existed, there are FAs from Chornobyl NPP three power units – over 21 thousand fuel assemblies (everybody knows where the fuel from Power Unit 4 is). Fuel assemblies at ISF-1 are kept in water (that’s why it is a wet type storage facility); this is allowable only during some limited time. But in total, this facility does not longer meet the up-to-date standards.

So that the fuel can be safely stored for a hundred years, an interim dry storage facility for spent nuclear fuel (ISF-2) was constructed at ChNPP industrial site. The history of its construction is not simple as the first contractor – French company “Framatome” – somehow ended up having made the building with cracks in its concrete body and could not decide how to remove water from the damaged FEs. However, in 2007, the project was taken on by US Company Holteс International and since June 2021, ChNPP has started the transportation of fuel from ISF-1 to ISF-2.

ISF-1 construction was funded from the Nuclear Safety Account (NSA) administered by the EBRD. The project will provide for acceptance for storage, preparation for storage and the storage itself for 100 years of 21,000 RBMK-1000 SFAs at the throughput of 2,500 SFAs per year (it means that the transportation of fuel from ISF-1 to ISF-2 will be carried out during about 10 years).

ISF-2 nominally consists of 2 modules. The first one is the Spent Fuel Processing Facility (SFPF) to where spent fuel assemblies (SFAs) will be transported in a special railcar. Inside the SFPF there is a “hot” cell where the SFAs will be cut into two halves (bundles), put into fuel tubes and those, in their turn, will be loaded into the custom-made steel double-walled shielded canisters (196 halves for every canister).

After drying (for removal of residual liquid) the canisters will be taken to the second module – the Spent Fuel Storage Area (SFSA), where the fuel will be stored in the special concrete modules during 100 years.

More details about ISF-2

CSFSF

As it is clear from its name, the Centralized Spent Fuel Storage Facility (CSFSF) is designed for the same thing as the ChNPP ISFs, namely to place the spent nuclear fuel for long time period. The only difference is that ChNPP ISFs place the fuel of Chornobyl NPP only and CSFSF will accept the fuel from other Ukrainian nuclear power plants. And here it’s important to pay attention to these two words, namely “fuel” and “Ukraine”. No sooner had a talk turned to CSFSF construction than the “enlighten” folks threw a mind-boggling tantrum, which, in general, can be verbalized as “In Ukraine a nuclear repository is built for radioactive waste from the USA and Europe”.  Both parts of this statement are false. First, storage of waste and storage of fuel have essentially different methods of preparation and placement. Secondly, there are international agreements (in our case, underpinned by the Ukrainian legislation) that oblige a country having nuclear power industry to bear the final responsibility for safe management of the nuclear fuel built-up at its NPPs. It means that the spent nuclear fuel of any country in the world cannot get to Ukraine. However, Ukraine must take back its own one. Until recent time all spent fuel from three Ukrainian NPPs, namely Khmelnytskyi, Rivne and South-Ukraine NPPs (since 2001, Zaporizhzhia NPP has run its own on-site storage facility) – at a considerable price, about 200 mln US dollars per year – was moved for interim storage and processing to Russia. All valuable elements were extracted in Russia from the VVER-440 SNF and the fuel – now as high-level waste – was returned, and SNF from VVER-1000 was in Russia just for the chargeable interim storage.

Very likely, the expenditures for CSFSF construction and operation will be fourfold lower than total expenditures incurred today by Ukraine moving SNF to Russia. After the commissioning stage is constructed, the spent nuclear fuel of Ukrainian NPPs will be placed at its own CSFSF. The design capacity of the storage facility is about 16.53 thousand spent fuel elements (12.01 thousand – from VVER-1000 power units and 4.52 thousand – from VVER-400); it will be enough for the entire period of Ukrainian reactors operation. The CSFSF lifetime is 100 years.

On December 22, 2020, with the participation of top managers of NNEGC “Energoatom”, Holtec International (the USA), JSC “Turboatom” (Kharkiv) and other companies who were involved in the project implementation, as well as at the presence of mass media, the first start-up complex of the Centralized Spent Fuel Storage Facility (CSFSF) was opened.

During the visit to CSFSF the journalists were convinced of the facility full readiness to receive the spent nuclear fuel from the Ukrainian NPPs for storage.

As of now, the construction of all civil structures and utilities for receiving and storing the spent nuclear fuel has been completed, as well as the site itself where the containers with spent fuel will be placed. Pre-commissioning and testing the equipment and components supplied by Holtec have started. The operation of the first start-up complex will start as soon as the 43-kilometer railway track is constructed to this storage facility and connects it to the railway network of Ukraine. Other 14 start-up complexes of CSFSF will have been built by 2040; simultaneously the Storage Facility site will be filled with SNF containers.

Source: SE NNEGC Energoatom

Vector Complex for radioactive waste management 

First, Vector located 17 km from ChNPP is intended for decontamination and subsequent storage (or disposal) of radioactive waste distributed around the Chornobyl Exclusion Zone. At a rough estimate, there are about 3 mln cubic meters of radioactive materials in the zone. The first commissioning stage includes a facility for RAW disposal in concrete reinforced containers (SRW-1) and a module facility for radioactive waste disposal in bulk (SRW-2) and necessary utilities (vehicle washing, radiological laboratory, changing facility etc.).

Furthermore, the radioactive waste built-up at Chornobyl NPP during the operation period and the waste to be produced during ChNPP decommissioning will be disposed here. Liquid and solid waste (LRW and SRW) following the relevant procedures at the Liquid Radwaste Treatment Plant (LRTP) and Industrial Complex for Solid Radwaste Management (ICSRM) will be moved to the Engineered Near Surface Disposal Facility for Solid RAW (ENSDF, capacity is 50,250 m³ ) at Vector. The first containers from ChNPP have been loaded there already.

And finally, the returned from russia HLW of SNF – products after processing of Rivne NPP VVER-400 reactors fuel that we mentioned above – will be placed here. This is vitrified high-level waste which cannot be used neither in nuclear industry or anywhere else. The waste from specialized integrated plants of Radon system will be handed over here too. Maybe, also RAW from other Ukrainian NPPs will be placed right here.

When the first row is filled with containers it will be poured with concrete and the next row will be stacked on it. When 4 concrete reinforced layers are complete, the disposal facility will be closed and covered with layers of clay and soil and grassed over. In such a way, the waste will be disposed for 300 years.

The international practice provides for two options of radioactive waste disposal: in deep geological formations underground or in the near surface disposal facilities. As for the geological repositories it is  hard with them in Ukraine (if such a facility starts to be built it will be not less than in 50 years but Vector complex is suitable in full. Firstly, it has a near surface disposal facility, secondly, it is situated within the Exclusion Zone).

What’s better: to take some mud from a clamp and put it into the nearest pit, or to take this mud in handfuls across the whole yard to some corner spattering it all around and taking a risk that in the clean up to this moment corner some person will get in it? It so fell out that in the area of 10-km zone it is impossible to settle within the nearest few thousands of years. Where is the good of polluting the rest of Ukraine?

In any case, all waste emplaced at Vector will be only of Ukrainian origin.

Here is an interesting document where you can find, for example, the information on the filling of existing RAW storage facilities of the operating Ukrainian NPPs which lets understand that very soon there will be no place to move RAW to, except to Vector.

Захоронения послеаварийных РАО

When urgent actions for mitigation of the Chornobyl NPP accident were taken in 1986-1987, some facilities to dispose and localize a great volume of accident RAW were established within the Exclusion Zone. They are RAW disposal sites, namely RWDS “Buriakivka”, “Pidlisnyi”, “ChNPP 3-rd Generation” and sites for temporary localization of RAW (RWTLS).

RWDS “Buriakivka”

RWDS “Buriakivka” is intended for disposal of solid low-and intermediate-level RAW which will be under administrative control within 30 years and under sanitary control within 300 years. The disposal site has been used since 1987 and it consists of 30 near surface facilities (trenches) for RAW disposal. The main engineered barrier providing the radionuclide containment is a specially constructed clay shield of 1 meter thick. Totally, since the start of operation, about 1330.5 thousand tons (665.25 thousand m³) of Chornobyl origin RAW were emplaced in “Buriakivka” facilities (trenches).

Moreover, in a specially made area within this RWDS there are radioactively contaminated vehicles, which were used during mitigation of the Chornobyl disaster.  In 2012, the SSE CERWM, subject to approval by the State Nuclear Regulatory Inspectorate of Ukraine, started dismantling and size-reduction of these vehicles.

Some years ago, as agreed upon with the Regulator, Buriakivka site was extended by 120 thousand meters of 6 additional disposal facilities between trenches.

<ore about "Buriakivka"...

Other RWDS

Non-operating currently RWDS “Pidlisnyi” and “ChNPP 3-rd Generation” were established in the first years of the ChNPP accident mitigation. In these facilities, the most dangerous high-level and long-lived accident-origin RAW were placed. Ideally, in the future the RAW should be retrieved from these sites and re-disposed in geological repositories. While Ukraine is searching for a decision as for a geological formation, the activities were carried out at these RWDS in 2012 aimed at protection against degradation and at maintenance of required containing functions of their engineered barriers, the additional barriers were constructed and the monitoring systems were improved.

RWTLS

Finally, within the Exclusion Zone there are nine sites for temporary localization of radioactive waste (RWTLS), namely “Yaniv Station”, “Naftobaza”, “Pishchane Plateau”, “Red Forest”, “Stara Budbaza”, “Nova Budbaza”, “Prypiat”, “Kopachi”, and “Chystohalivka” with the total area of about 10 hectares. These about 1,000 trenches and clamps with RAW are hastily made sites where everything possible were put and buried. They are continuously monitored and from time to time their content is re-disposed in other places if any risk of flooding etc. emerges.

“Rozsokha”

The most famous of temporary localization sites for RAW is “Rozsokha”. It is the now-defunct 20-hectare “terminus” for contaminated vehicles where the machines were located to wait for natural reduction of dose up to the acceptable values.

What does “reduction up to the acceptable values” mean?

If you look at the table of radioactive element half-lives, you can see that for different radioisotopes this half-life makes from 28 years (Strontium-90) to 24 thousand years (Plutonium-239). Here, a lot of people falsely assume that if a half-life makes 28 years then the total lifetime makes 28 * 2 = 56, but it is not true.

No matter, what is the initial quantity of Strontium-90, in 28 years exactly half of this quantity will remain, in the following 28 years – one quarter, in another 28 years – one eighth, and so on. In order to understand the approximate time of total decay it is necessary to multiply the hall-life by 20. For example, for Strontium-90 the time of total decay makes about 560 years (and for plutonium, respectively, half a million years). If we know what isotopes contaminated the environment or machinery we can estimate the time period within which it is impossible to settle in the zone or how many years will pass till it is allowed to melt down the machinery.

Currently, all vehicles from “Rozsokha” have been fragmented or “repeatedly put into economic use”.