We were contracted to support the design validation of the Export Transport Bogie, Recovery Bogie and End Stop structures, providing additional capacity to a busy project team and additional capability through our knowledge of non-linear dynamic finite element analysis (FEA). Our approach allowed design changes to be tested in real time.
Our client, working as part of a consortium, were tasked to deliver elements of a facility capable of importing and storing Intermediate Level Waste (ILW) packages, derived from the high hazard plants located on Europe’s most complex nuclear site at Sellafield.
The project, known as the Box Encapsulation Plant Product Store with Direct Import Facility (BEPPS DIF), incorporated the re-design and fit out of a purpose built, above ground nuclear waste store and the construction of a new direct import facility to handle radioactive waste.
We were contracted to support the design validation of the Export Transport Bogie, Recovery Bogie and End Stop structures, providing additional capacity to a busy project team and additional capability through our knowledge of non-linear dynamic finite element analysis (FEA).
We were tasked to structurally assess pieces of bespoke equipment that had been designed expressly for the Intermediate level waste transfer system. The equipment included the Export Transfer Bogie, Recovery Bogie & End Stops and these function as follows;
- The Export Transfer Bogie is utilised as part of the day to day operation of the plant, facilitating the safe transfer of ILW packages which are lowered into place onto the bogie and constrained via a set of corner guides, supported by energy-absorbing crush pads and secured through self-weight. Motorised wheel blocks provided translation of the bogie with the control and electrical supply provided by an adjacent conductor rail.
- The Recovery Bogie was developed to recover the Export Transfer Bogie in the event of a power or mechanical failure – this was operated by a manual winch.
- The End Stops were part of a multi-level safety approach, providing an ultimate end stop capability should control, and sensors fail and the bogie attempt to travel beyond its designated interfaces.
We assessed all equipment for operational and accidental cases, for example, the Recovery Bogie pushing the Export Transfer Bogie back to the facility due to wheel failure and the uncontrolled lowering of a Waste Container onto the Export Transfer Bogie.
We used a mixture of hand calculations, static FEA, and explicit dynamic FEA for the assessment. Over forty-five load cases were considered, including; lifting of the two bogies, validation of extreme rail tolerance loads, lowering of the waste package under normal, misaligned and uncontrolled conditions and impacts into end stops. Depending upon the application there were two primary codes considered; BS 2573-1: 1983 Rules for the design of cranes and BS EN 1993-1-1: 2005 Eurocode 3: Design of steel structures.
Where possible, we used traditional hand calculations – utilising PTC Mathcad for this purpose as the parametric nature of the software allows us to test and reflect changes rapidly.
Where necessary, such as for statically indeterminate or dynamic problems, FEA models were developed. These were mainly composed of high order shell and solid elements, with a complex joint methodology set up to accurately represent bogie wheel degrees of freedom and effects of rail tolerance where applicable.
All calculations and analyses were reviewed and approved by our ISO 9001: 2015 certified Quality Management System and, where applicable, reporting was developed to meet the Sellafield Ltd ‘Design Guide for the Presentation of Finite Element Analysis Reports’ – ES_0_0004_Issue 1.
Ultimately six calculation packages totalling nearly 400 sheets were developed, reviewed, approved and various design changes were proposed, validated and implemented. Through this process, the ability of the equipment to meet the structural, operational and safety requirements of the facility was validated.
- A parametric calculation approach allowed design changes to be tested in real time.
- The risk of the equipment failing in service was minimised; there was confidence that the safety case objective could be met.
- By leveraging the technical team at PDL, the desired project timescales could be achieved