Helium Storage and Transfer Subsystem design description. Revision

The Helium Storage and Transfer Subsystem (HSTS) consists of two parts. The first consists of nine (9) high pressure storage tanks containing helium at 15.6 MPa (2250 psig). These tanks provide makeup and purge helium at a rate of 1216 kg per y (2680 lb/y) to the various helium users, including circulator bearing seals, analysis packages, and cooling system surge tanks. The second, larger part of the system, provides for the low pressure storage of 6078 kg (13,400 lb) of primary coolant helium in 180 storage tanks at 7.0 MPa (1000 psig). The system serves all four (4) reactor modules. The low pressure storage part of the system receives helium from the discharge of Helium Purification Subsystem (HPS) and is activated during depressurization and pumpup operations only. It is not required to operate continuously. Storage capacity is provided for primary helium coolant from two reactor modules. However, since depressurization and pumpup operations are performed for only one reactor module at a time, two 50% capacity low pressure transfer compressors are provided having a total transfer capacity of 340 am{sup 3}/h (200 acfm) which is sufficient to service one module. High pressure helium is supplied continuously to all the four reactor modules simultaneously from the high pressure storage tanks. These tanks are replaced periodically with fresh tanks