Mechanical engineering note - safety analysis of molten uranium/water interaction in the uranium foundry furnace Page: 14 of 84
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5.2 System Response
The Primary system response to a water leak occurs inside the vessel and is provided by
the operation of the roughing pump, which will maintain a low hydrogen and steam
inventory in the vessel. If the primary response is defeated the system has two back up
responses. The first back up is to vent the chamber using two pressure relief valves. If
either or both of the pressure relief valves malfunction, the second back up is to vent the
chamber through a rupture disc. The details of the system response to a chamber over
pressure are shown in Fig. 6, and described below.
a. Ion pressure gauge, IG-1 (see Fig. 4), inside the vessel sense a pressure rise from the
normal operating pressure of <10- Torr. If the pressure rises to greater than 6 x 104
Torr, the control system automatically shuts off the induction power supplies, closes
the cryopump isolation valves V-1 and V-2 and sends an alarm to the operator.
b. If the pressure rise sensed by the convectron gauge, CG- 1, is below 30 mTorr, the
operator may reopen the high vacuum isolation valves (V-1 and V-2) in an attempt to
continue operation. If the pressure is reduced to 10-6 Torr range by this action then
the induction power supplies can be manually turned back on. If the pressure is not
reduced to 10-6 Tort range, the operator must identify the gas source or terminate the
c. If the convectron gauge, CG-1, reports a pressure rise greater than 30 mTorr, the
control system automatically opens the roughing isolation valve V-5, allowing the
roughing system to pump on the vessel. If the pressure stabilizes below 30 mTorr,
then the operator may attempt to cross back over to high vacuum. When the
convectron gage senses chamber pressure greater than 1 mTorr the ion gauge shuts
off independently of the control system as well as closes the RGA isolation valve to
protect equipment and to eliminate a possible ignition source.
d. The roughing pump has a capacity of 3200 cfm and the pump exhaust is connected to
the negative air system to prevent the possibility of releasing any contaminant into
the atmosphere. The worst case scenario described in Section 5.1 will only occur if
the rough pump fail to pump the vessel.
e. If the convectron gauge CG-1 indicates the chamber pressure > 20 Torr and the flow
sensor indicates a decrease of coolant flow below the setpoint, then the system
response as if there is a major water leak inside the chamber. The control system
then automatically closes both inlet and outlet control valves of that cooling loop to
minimize water egress into the chamber and sends an alarm signal to the operator.
Water in other cooling loops continues to flow. The objective of this action is to
limit the amount of water available to potentially react with molten uranium. If the
solenoid valves fail to stop the cooling water, the operator can manually close two
ball valves to shutoff the water flow.
Each cooling loop has two water pressure relief valves for redundancy to prevent
over pressure in the cooling lines. If the cooling line pressure buildup to 150 psig or
210*F, the pressure relief valve will vent the line pressure into the closed loop water
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Gourdin, W H & Sze, J. Mechanical engineering note - safety analysis of molten uranium/water interaction in the uranium foundry furnace, report, August 19, 1999; California. (digital.library.unt.edu/ark:/67531/metadc622935/m1/14/: accessed December 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.