Liquid high-level waste (HRW) is the greatest danger because of its high specific activity and long-lived radionuclides. The procedures for handling liquid HRW require waste solidification in the super-rigid matrix. The solidified product must be placed for long-term storage, and potentially for final disposal in a deep geological formation.
At present, one of the major matrix materials is glass. According to the procedure applicable at Mayak PA, the vitrified HLW is loaded into special cans, and then full HLW cans are placed into two-cell or three-cell canisters. An important problem for safety assessment of the HLW final disposal is the obtainment of data on the chemical composition, radionuclide content, activity and other characteristics of the vitrified HLW.
In 2021, Sosny R&D Company designed and fabricated the equipment for core sampling from the cans with vitrified HLW, placing the core samples into tight ampoules and loading the full ampoules into a ТUК-19 transport cask for shipment to the research study.
This equipment includes:
- a sampling facility with the local control system,
- ampoules for sample transportation in a TUK-19 cask,
- an ampule clamping system,
- a basket for the ampule clamping system / HLW can,
- a grapple for empty ampule transfer with a hoisting equipment,
- a cooling water supply, collection and filtration system,
- a transfer cask for ampule transportation between the hot cell and a TUK-19 cask, and for loading the core sampler into the ampule,
- a shielded plug for placing a transfer cask above the airlock in the hot cell ceiling,
- a canister grapple for transportation of the canister with its lid cut off from the hot cell to the solid waste handling area,
- a facility for vacuum drying of the can with vitrified HLW before it is sent back to the storage facility,
- a basket for ampules with samples to be arranged inside TUK-19 cask,
- equipment for handling TUK-19 cask (a service platform, a guide plate, a support for ТUК-19 cask lid, a leak test facility).
We checked the functionality of some parts and assemblies, and tried out some process operations and conditions for glass sampling at the mockup sampling facility. Based on the results of the core drill mock-up testing, we selected an optimum design for the sampling facility and determined the drilling conditions.
The sampling facility is for the operations in the hot cell. Before using a core drill, it shall be fixed onto the rotating support that can move the core drill away from the in-cell rotary vise for loading and removal of the equipment and a can with vitrified HLW, and enables core sampling in the boundary areas of the HLW can.
The core drill has a rod with the diamond core bit at its bottom. Three load cells monitor the longitudinal load on the core bit. The core drill is for drilling a hole in glass at the depth up to 900 mm, taking a core sample, breaking it off and loading the core sample into an ampule. Also, the core drill can make a hole in the upper part of the HLW can body.
After drilling, the core sample remains fixed in the sampler by a clamping device. The transfer cask serves to put the full core sampler in and take it out of the ampule.
The sampling facility is controlled remotely from a control panel in the operator’s room.
Specifications of the sampling facility:
|Safety class||4 according to NP-016−05|
|Dimensions (LxWxH)||1225x750x3970 mm|
|Minimum continuous operation time||6 h|
|Diameter of core sample||47.6 mm|
|Maximum height of core sample||900 mm|
An ampule for core sample transportation in a ТUК-19 cask is equipment of safety class 3, according to NP-016–05. A vitrified HLW sample is loaded into the ampule together with the core sampler. The ampule plug has two spring-loaded locks, radial seals and a pintle.
A clamping system keeps an ampule and opens its locks when removing/inserting the ampule plug. It has some elements for centering the ampule. The ampule clamping system is operated manually by using the manipulators.
A cooling water supply, collection and filtration system supplies water to the core rod, collects water from the glass inside the HLW can, purifies water from the cutting products, and drains water to the hot cell drainage system.
A vacuum drying facility comprises a vacuum chamber for the HLW can, a vacuum pump and a control system. After vacuum drying, the maximum volume of moisture remaining in the can with vitrified HLW is 10 g/m3. The vacuum pump removes the environment of the vacuum chamber into the process vent system of the hot cell.
A basket for ТUК-19 caskis a part of the ТUК-19 transport packaging. It serves to transport three ampoules with vitrified HLW samples inside the ТUК-19 package (one ampule per each of the three guide tubes). The basket has perforations to ensure circulation of the cooling air and drainage of water/decontamination solutions.
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