Pressure safety approach for PIP-II cryogenic distribution system and cryomodules

TL;DR

This paper presents a comprehensive pressure safety approach for the PIP-II cryogenic system, detailing relief sizing, heat flux analysis, and safety measures to prevent over-pressure hazards in a superconducting linear accelerator.

Contribution

It introduces a detailed pressure safety methodology tailored for the PIP-II cryogenic distribution system, including relief sizing and hazard mitigation strategies.

Findings

Relief device sizing for all cryogenic volumes

Heat flux determination methods for safety analysis

Ventilation strategies for tunnel relief scenarios

Abstract

The Proton Improvement Plan-II (PIP-II) is a superconducting linear accelerator being built at Fermilab that will provide 800 MeV proton beam for neutrino production. The linac consists of a total of twenty-three (23) cryomodules of five (5) different types. Cooling is required at 2K, 5K and 40K. The Cryogenic Distribution System (CDS) consists of a Distribution Valve Box, ~285 m of cryogenic transfer line, modular Bayonet Cans to interface with cryomodules, and a Turnaround Can. The cryogenic system must provide protection from over-pressure by sizing pressure relief devices for all volumes and process line circuits. The cryomodule cavity circuits have dual pressure ratings, 4.1 bara when cold and 2.05 bara when warm (T>80K). Worst case relieving cases will be identified. The methods for determining heat flux will be presented. For the relieving occurring in the linac tunnel, flow must vent to outside to avoid an oxygen deficiency hazard. Also, we will present vacuum vessel relief sizing to protect the cryogenic distribution system vacuum shells from over pressure during an internal line rupture. The project is funded by US DOE Offices of Science, High Energy Physics.