Spent Fuel Management at the Chornobyl NPP
Spent nuclear fuel is managed on the site of the State Specialized Enterprise “Chornobyl NPP” (henceforth ChNPP) according to SNRIU licenses ЕО No. 000040 “ChNPP Decommissioning” (issued on 22 March 2002) and ЕО No. 000859 “ChNPP ISF-1 Operation” (issued on 25 June 2008).
The operator, SSE Chornobyl NPP, currently performs the activities related to implementation of the following:
- “Plan of ISF-1 Safety Improvement Measures” approved by the SNRIU on 24 June 2008;
- “Plan of Safety Improvement Measures for ChNPP Nuclear Facilities” approved by the SNRIU on 12 December 2011;
- “Plan of Measures to Implement the Process of Stabilization, Transfer and Storage of Special Canisters Containing Damaged Spent Fuel” approved by the SNRIU on 25 March 2014 (efforts aimed at transfer and storage of damaged fuel assemblies from reactor spent fuel pools at power units No. 1 and 2 to ISF-1 SFP is planned during 2015 according to the stated Plan of Measures).
The majority of spent fuel assemblies (SFA) is stored in the spent fuel pool (SFP) of the spent fuel wet storage facility (ISF-1), which was put into operation in 1986. ISF-1 is currently operated according to SNRIU license No. 000859 of 25 June 2008. The rest of spent fuel is stored in spent fuel pools at ChNPP units No. 1 and 2.
According to the National Program for Chornobyl NPP Decommissioning and Shelter Conversion into the Environmental Safety System, spent nuclear fuel should be removed from power units No. 1 and 2.
There is no SNF at ChNPP unit No. 3, and further use of the spent fuel pool at this power unit is not envisaged for spent fuel storage. Considering the above, on 07 December 2012 the SNRIU agreed the decision of ChNPP “On Consideration of Power Unit No. 3 a Radwaste Management Facility”. Thus, starting from 08 December 2012, ChNPP unit No. 3 is considered a radwaste management facility.
Resulting from stress-test of power units No. 1, 2, 3 and ISF-1 conducted in 2011, ChNPP developed and agreed with the SNRIU the following:
- “Plan of Safety Improvement Measures for ChNPP Nuclear Facilities”;
- “Decision on Location and Storage of Spent Nuclear Fuel (except damaged one) Accumulated During Operation of Power Units No. 1,2, and 3 in ISF-1 Spent Fuel Pool Section 5”.
ISF-1 lifetime specified resulting from safety review in 2011 expires in the end of 2025. Thus, a new spent fuel dry storage facility (ISF-2) is under construction for long-term safe storage of SNF on ChNPP site.
Project for Completion of Spent Fuel Dry Storage Facility at Chornobyl NPP (ChNPP ISF-2)
Since spent nuclear fuel at three NPP units is still stored in ISF-1 operated since 1986 and due to the fact that the lifetime of the storage facility is limited, it was decided to construct a new spent fuel dry storage facility (ISF-2).
According to Andrii Savin, Chief Engineer of the Project, ISF-2 was designed for long-term storage during 100 years for spent fuel at Chornobyl NPP 1-3. The Client of facility construction is SSE Chornobyl NPP, and General Subcontractor is American company Holtec International.
Several Ukrainian enterprises perform construction activity, namely: Utem-Engineering, Ukrtransbud, Energoprominvest, etc. Companies from many countries of the world including Ukraine deal with equipment supply.
About 200 workers are currently involved in ISF-2 construction. Two shifts of 140 workers will be involved to ensure day-and night operation of the facility, 17 persons will be involved into technological process. Now, 80% of construction work was completed, the remaining 20% include mounting completion and testing.
Spent nuclear fuel processing and storage: how will operate ISF-2?
After ISF-2 commissioning, special container car will transport nine fuel assemblies from the existing storage facility to new one. The frequency of spent nuclear fuel transport and processing is 2.5 thousand fuel assemblies per year. Thus, 9.5 years are required for transport of all fuel elements and their processing. Car will enter the facility building for fuel preparation for storage.
Spent nuclear fuel for Chornobyl NPP is specific and differs from fuel for other reactors since it consists of the lower and upper fuel bundles. Thus, fuel elements should be divided into bundles and packaged into canisters; canisters should be transported for storage in helium environment.
Spent nuclear fuel processing cycle is significantly complicated. After spent nuclear fuel arrival to ISF-2, a special container will be put from horizontal to vertical position; the container will include a cover with nine fuel assemblies. It will be withdrawn and lifted to the so-called hot cell, that is, the main room for fuel processing. The whole equipment used in the hot cell was already manufactured. Most of it shall be in a newly constructed building of the facility, equipment shall be mounted.
The canister to be placed in concrete storage modules is made of stainless steel and is double-walled. After canister filling, spent nuclear fuel will be dried to form safe conditions for further storage, covers will be welded, and helium environment will be created inside for heat removal and storage during 100 years. Canisters will be transported to concrete storage modules and put in horizontal position to special cells.
In general, 231 canisters will be installed 229 of which will be used for spent nuclear fuel storage and two of them will be redundant. During spent nuclear fuel storage, visual inspection of canister surface will be performed by means of special equipment, radiation monitoring, temperature measurement, etc. Only a few canisters will be withdrawn periodically once per ten years (according to the requirements of the nuclear legislation of Ukraine) from concrete cells for more comprehensive monitoring (measurement of helium density and additional radiation monitoring) and safety review. If repackaging is required, it may be performed in redundant canisters. Holtec International supplies canisters from the USA – 45 units are already at the site.
Andrii Savin underlined that the matter is currently not final disposal but fuel storage during 100 years. After transfer of all fuel assemblies to ISF-2, operating ISF-1 will be decommissioned.
The completion of ISF-2 equipment mounting is planned in spring 2016, and further cold testing of individual equipment and systems without spent fuel assemblies will be performed.
The comprehensive tests of ISF-2 (without spent fuel assemblies) in whole will start in the second quarter of 2017.
Hot tests with spent fuel assemblies are planned in the fourth quarter of 2017; subsequently, appropriate decision should be approved by the State Nuclear Regulatory Inspectorate of Ukraine. 186 spent fuel assemblies will be transported from ISF-1 to ISF-2 under hot tests. A license for facility operation will be issued after completion of the tests. The final commissioning will start in the third quarter of 2018.
It is necessary to note that the centralized spent nuclear fuel storage facility for three Ukrainian NPPs, namely Rivne, Khmelnytsky and South Ukraine NPPs, will be constructed at the distance of 18 kilometers from ISF-2 the Client of which is the Energoatom Company.