Process engineering support functions for the Spallation Neutron Source (SNS) mercury loop/target system.
SPALLATION NEUTRON SOURCE MERCURY SYSTEM PROCESS DESIGN
The client contracted Process Engineering Associates, LLC (PROCESS) to perform process engineering support functions as required for the Spallation Neutron Source (SNS) mercury loop/target system. The SNS is a neutron scattering research user facility for fundamental research located at the Oak Ridge National Laboratory Facility.
Specifically, PROCESS was assigned the following major project tasks:
- Task 1 – Develop process control diagrams (PCDs) and piping and instrumentation diagrams (P&IDs)
- Task 2 – Perform a process design for a vent stream mercury condenser
- Task 3 – Execute a relief system evaluation for the mercury loop
- Task 4 – Perform a mercury migration analysis for the system piping
- Task 5 – Prepare a process flow diagram (PFD) for the mercury loop system and associated utilities
- Task 6 – Perform a detailed evaluation of the mercury heat exchanger design.
Task 1 involved developing PCDs and P&IDs for the system from initial block flow diagrams prepared by the client. For the PCD, PROCESS executed a process control system design for the mercury loop/target system and performed line sizing calculations for the primary system process, helium, vacuum, and vent lines. The PCDs were upgraded to P&IDs for the purpose of depicting additional process and control system details and for integrating the drawings with those produced previously by PROCESS for the SNS utilities systems. Task 2 involved preparing a process design package for a condenser system designed to remove mercury from a system vent stream. A process design basis was developed for the purpose of defining condensing system capacity and performance requirements. Mass and energy balance calculations for the condenser system were developed using commercial computer process simulation software, and a process control scheme for the system was developed. The mass and energy balance information and controls were depicted in process flow and control diagrams that were prepared for various venting scenarios. The simulation software was also used to calculate the condenser heat transfer area, and an equipment duty specification was prepared for the condenser. Finally, a cost estimate for the purchase of the system major unit operations was prepared. Task 3 included a detailed evaluation of a rupture disk system proposed for mitigating overpressure scenarios for the mercury loop/target system. PROCESS identified all credible relief scenarios, determined relief requirements for all credible scenarios, and calculated pressure relief line sizes based on the requirements using the simulation software pipe simulator package. Task 4 included the development of diffusion calculations for mercury vapor transport through the piping exposed to mercury for the purpose of predicting mercury concentrations versus time in the piping outside the system containment area. Task 5 involved the preparation of a PFD depicting all mercury loop major unit operations and primary stream mass and volumetric flow rates, temperatures, pressures, and compositions for all process and utilities (cooling water, helium, nitrogen, and offgas). Task 6 involved the evaluation of the mercury heat exchanger detail design executed by the selected equipment vendor. As part of this task, PROCESS evaluated the exchanger performance using licensed heat exchanger evaluation software. Accurate simulation of the exchanger operation using the software was particularly challenging due to its configuration (double-wall) and due to the process materials involved (mercury). PROCESS’ evaluation resulted in the discovery of several exchanger design issues that required correction prior to equipment fabrication.
As part of this project, PROCESS also performed several additional mass and energy balance and vapor-liquid equilibrium calculations for the system as required by the client.
- Governmental Research
- Mass and energy balances
- Process flow diagram (PFD) and process control diagram (PFD) creation
- Heat exchanger evaluation
- Basic engineering design (BED)
- Pressure relief valve (PRV) or pressure safety valve (PSV) evaluation