The Segmented Drum Scanner Facility is the first and only licensed facility in South Africa to assay drummed nuclear waste non-destructively. The Segment Drum Scanner (SDS) has the ability to quantify all the relevant nuclides in nuclear waste. Nuclides in the waste are measured or inferred by the SDS. The facility is managed by Nuclear Waste Management Services.

The purpose of the segmented drum(SDS) scanner is to perform non-destructive assay on drums of nuclear waste. The assay results are used to determine whether the drum content meet the acceptance criteria for further processing, disposal or transfer to an interim storage.

The SDS is an automated facility for assaying drums of nuclear waste. Each waste drum presented for assay is identified by an unique barcode number which is recorded in a database. The database contains historical data pertaining to the origin , geometry and contents of the drum. The SDS measures gamma vision emission from the drum over a wide energy spectrum and then computes the drum inventory from the measurement and other inferred characteristics which are determined by prior characterisation of the waste stream. The result is used to classify the contents of the drum in accordance with the waste classification scheme. After the classification, the drum is marked by spraying coloured rings around the circumference to assist operators in handling. The classification is also recorded in the database which serves as the primary record of the drum inventory and history

The SDS facility consists of the following:

A drum reception area with a gravity conveyor.

A driven conveyor system for moving the drums to the SDS.

A bar code reader which identifies the waste drum.

The Segmented Drum Scanner.

A driven conveyor system which moves assayed drums from the SDS to a colour coding booth.

A colour coding booth where a set of coloured rings (which identified the waste class into which the drum has been sorted) are sprayed onto the drum.

A driven conveyor which moves the marked drums from the colour coding booth.

A gravity conveyor for moving the drums to the dispatch area.

A programmable electronic system which reads the bar code on the drum. controls the SDS and conveyor system to ensure the orderly flow of drums through the process, and transmits the assay result to a central database.

Drums are delivered by road to the reception area in the facility. No drum is accepted unless it is accompanied by the necessary documentation. On acceptance the drums are off-loaded for further processing. Rejected drums are returned to the dispatching facility. Drums may be either be loaded directly on the conveyor or temporarily stored in the receiving area.

Figure 1: Receiving area and conveyor system

The drums are moved manually along the gravity conveyor system until the reach the driven conveyor which feeds the SDS. The driven conveyor is controlled by the sequencing PLC which controls the identification and orderly progress of the drums through the scanning system. A optical sensor is used to sense the presence of the drums on the conveyor and prevent overloading.

When the scanner is ready to accept a drum, the operator initiates the process by actuating a switch. The conveyor feeds the drum to the weighing system, the drum is weighed and the result is stored in the PLC for subsequent use. The system then moves the drum onto the scanner turntable. The operator then manually initiates the measuring process from the control computer and selects the applicable waste stream as indicated on the batch list.

Figure 2: Drum on turntable while its rotating and lifting

The system reads the barcode and scans the drum by lifting and rotating the drum to through a scanning sequence which allows the detectors to acquire typically 12 segments of the drums. The average duration of the sequence is about 300 seconds. Upon completion of the sequence the turntable is halted, the drum is unloaded and the spectral data are analysed. The results are interpreted in accordance with the approved interpretation model for the specific waste stream and waste type.

Figure 3: Operator panel with measure spectra of the drum content

Drums which satisfy the appropriate criteria are marked in the spray booth The marking consists of coloured rings sprayed onto the circumference of the drum. Drums which do not meet the criteria are rejected. Drums which have been rejected pass through the system without been marked and are set aside for investigation and correction of the problem which cause the problem.

Figure 4: Colour coding booth where drums are marked

Marked drums are removed from the conveyor for dispatch to the appropriate destination undercover of a computer generated drum transfer certificate.

Figure 5: Drums on the conveyor after is was marked in colour booth

Figure 6: Drums ready for dispatching