Alcator C-Mod

Test Procedure for Diborane Gas System

Version: Version 3.3 Released 7/5/2002 by C. Fiore. Reviewed by J. Irby, E. Marmar

Date: 1/9/96 revised 7/5/2002

Date: Translated to HTML 7/03/2002

Computer filename: User10:[fiore.www]dibtest.html

System: Diborane Gas System

Person responsible: C. Fiore, G. Dekow

I. Introduction

It has been postulated that an effective way to coat the walls of the Alcator C-Mod vacuum vessel with a thin layer of boron is to create a gaseous discharge in diborane gas inside the vacuum vessel. Diborane is highly toxic and flammable, and presents an explosion hazard. The gas delivery system must be of high integrity and leak free. Leak detection and remote control are essential. Procedures for handling, maintenance, process, and emergency response are required, as is training of any personnel directly or peripherally involved with using this material.

II. Required Elements:

A.

Scope/Purpose This document covers the testing requirements for the Alcator C-Mod Diborane facility.

B.

Consequences of procedural failure.

Failure to adequately test the diborane system could result in leakage of diborane gas into the cell or into the diborane housing, which could lead to fire or explosion, or to personnel exposure to toxic gas. Diborane is immediately dangerous to life and health at 40 ppm, and an explosion hazard at 9000 ppm.

C.

Definitions

MDA-TLD-1-Gas monitor for the diborane system. One is located at the diborane gas cabinet. The other is located on the igloo, first level under B-port.

SCBA-Self Contained Breathing Apparatus. Two units are located at the entrance to the C-Mod power room, in the control room.

D.

Responsibilities

Test of the performance of the system will be conducted by Joe Bosco, Gary Dekow, and Bob Childs with Catherine Fiore in attendance.

Installation of the diborane gas cylinder: Two persons, trained and approved to wear SCBA, trained in diborane hazards, and trained in all of these procedures will install the diborane gas bottle.

These procedures will be reviewed and approved by a committee of no fewer than 3 knowledgeable persons, appointed by the Safety Officer.

E.

Required Equipment

SCBA

Adapter for helium gas bottle to diborane bottle fitting

Helium leak detector ("sniffer")

Wrenches for gas fittings

Walkie-talkies or cell phones

F.

Required Materials

G.

Assumptions and Prerequisites

The PLC system has been installed and completed.

The diborane system has been installed and completed.

All alarms and warning systems have been installed and completed.

A tv camera for remote viewing of the toxic gas cabinet has been installed and is functional.

H.

Procedure

Check function of the diborane monitors (MDA-TLD-1).

1.

If this test is being done prior to installation of the diborane gas bottle, open valve PV5 in order to observe that it is closed during simulated fault conditions. The access control bit must be jumpered out in order to open PV5. If the diborane is in the toxic gas cabinet, do not open this valve.

2.

Turn the Tape Load Lever to the ``open'' (9 o'clock) position, remove the Chemcassette, and press the Alarm Test Key. The green System Status Indicator will flash. The display will show the word ``VERIFY''.

3.

Insert the test card with position#1 centered in the Detector Head; be sure that the colored chip on the test card faces up and that the card is inserted fully into the Detector Head.

4.

Close the Tape Load Lever and press the Alarm Test Key. The instrument will beep once.

5.

Open the Tape Load Lever and reverse the Test Card, centering position #2 in the Detector Head.

6.

Close the Tape Load Lever and press the Alarm Test Key. If all electronics and optical systems are operating properly, the instrument will go into an alarm condition, with both the audible and visual alarms activated and the alarm relay energized. Check that the process gas valve PV5 has closed if it was opened for this test. Note that the 4-20 mA output will deliver a signal equivalent to 100 ppb to the DIBORANE PLC.

7.

Open the Tape Load Lever and press the Alarm Reset Key. Rethread the Chemcassette Detection Tape and turn the Tape Load Lever to the closed (6 o'clock) position. The test is now complete.

8.

Repeat steps 1-6 for the second monitor.

Vacuum system test procedure

1.

Helium leak check system to 1×10^-7 scc/s from the gas bottle to the Piezo-electric valve by one of the following two methods:

Plug the diborane gas bottle connection. Set the helium system regulator to 30 psi, and open manual valve MV2 to pressurize the system. PV4, PV5, PV3, PV6 and MV1 must be opened. The diborane regulator (REG1) must be set to 30 psi. Use a helium sniffer to check all pressurized points in the system for leakage.

Install the leak checker at the point where the diborane gas cylinder is to be installed. Open the helium system regulator REG2 (make sure the helium bottle valve is closed), and open manual valve MV2. PV4, PV5, PV3, PV6 and MV1 must be opened. The diborane regulator (REG1) must be opened as far as possible. Pump the system out, start the leak checker, and spray helium on the system connections to look for leaks.

PLC safety system test.

Note that the access control bit must be jumpered out in order to open PV5 for these tests. DO NOT TEST PV5 INTERLOCKS WITH DIBORANE.

1.

Install helium gas bottle in the place of the diborane bottle. Note that an adaptor is needed to mate the helium bottle to the diborane connector. Open the valve on this bottle.

2.

Open the nitrogen gas bottle valve for the venturi system and set the regulator REG3 to 100 PSI. Open the helium purge gas valve and set the regulator REG2 to 30 PSI. Open PV3 and PV4. Set the diborane gas regulator REG1 to 30 PSI. Close PV4. Open PV1, and PV2 to evacuate the line. Verify that the diborane transducer TR4 is registering a vacuum and note the reading.

3.

Open PV5 and note that the diborane transducer TR4 registers an increase in pressure. Note the value. PV5 should close on all of the faults to be tested, which will register as a decrease in the pressure measured by the diborane transducer TR4. Should PV5 fail to close on any of the tests, the test should be considered a failure. Close PV5.

4.

Open PV5. Simulate a fault on the diborane cabinet MDA-TLD1, as described above in the section on testing the MDA-TLD1's. Note PV5 status. Reset. Close PV5.

5.

Open PV5. Simulate a fault on the B-side (cell) MDA-TLD1, as described as described above in the section on testing the MDA-TLD1's. Note PV5 status. Reset. Close PV5.

6.

Open PV5. Turn off cell exhaust blower. Note PV5 status. Reset. Close PV5.

7.

Open PV5. Close dampers on the diborane exhaust line. Note PV5 status. Reset. Close PV5.

8.

Open PV5. Close vaporizer valve MV5. Note PV5 status. Reset. Close PV5.

9.

Open PV5. Close house air valve MV6. Note PV5 status. Reset. Close PV5

10.

Search and lock the cell, placing it in full access control. Open PV5. Breach access control system. Note PV5 status. The system safety interlock test is now complete.

11.

Reset the system. Close the valve on the helium gas bottle (at the diborane input point) and open PV5 to evacuate the line. Close PV2, PV3, PV1, MV1 and close the diborane regulator REG1.

Inert gas test

1.

Install the helium gas bottle in the space provided for the diborane bottle, as described in the diborane gas installation procedure. Note that an adaptor is needed to mate the helium bottle to the diborane connector.

2.

Search and lock the cell. Enter the cell under controlled access to perform the next 2 items.

3.

Verify that manual valves MV1 and MV3 are open. Verify that the diborane regulator (REG1) is set to 30 PSI, the venturi regulator (REG3) is set to 100 PSI, and the helium purge gas regulator (REG2) is set to 30 PSI. PV3 and PV4 and manual valve MV2 will have to be open to set the diborane regulator pressure.

4.

Start the flow from the vaporizer into the diborane vent work and the vacuum pump outlet by opening ball valve MV5 and the valve going to the torus roughing pump. Verify that MV4 is open.

5.

Activate the purge procedure from the PLC. The AUTO switch on the DIBORANE PLC must be enabled, and the toggle switch for the diborane bottle valve should be in the closed position. Enable PURGE60. The PLC should open PV valves 1,5,3, and 6.

6.

Observe the purge cycle. PV2 will open, causing a drop in the pressure measured by the diborane transducer TR4. PV2 should then close and PV4 should open for 15 seconds, causing an increase the pressure measured by the diborane transducer TR4. PV4 will then close, and PV2 will open for 15 seconds. This sequence will repeat 20 times.

7.

At the end of the purge cycle, PV4 will close, and then PV2 will close 15 seconds later. PV1, PV5, PV2, PV3, and PV6 will now close. This is the end of the purge sequence, and the discharge cleaning is ready to commence.

8.

Enter the cell under controlled access, taking 2 walkie-talkies with them. One should don the welding glove and open the diborane (helium) bottle while the other watches the toxic gas detector on the cabinet. After exiting, enable the DIBORANE OPN bit on the PLC.

9.

Set up for the discharge cleaning cycle. Enable the Diborane on button on the DIBORANE PLC. Go into the TORVAC PLC. Turn off all filaments specified (IGT, IGP1, IGP2, both RGA's, the Ratiomatic.) Close all of the diagnostic gate valves. Close GV3. Close GV2. Close GV1. Open SV3. Open SV4 to 100. Open GV2. Turn IGP1 back on. If the pressure on IGP1 is less than 5×10^-5 Torr turn on the Dycor RGA. Go into the AFILL screen of TORVAC and clear the fault, even if no fault is indicated.

10.

Set the pressure by entering a requested pressure into the DIBORANE PLC and enable the fill request. PV5, PV3 and PV6 must all open. It will ask for a password (FILL) in order to proceed. Activate the diborane discharge cleaning mode from TORVAC.

11.

Verify that all systems function as expected. Set the piezo electric valve for the desired value and initiate the discharge cleaning. Verify that a discharge has formed in the machine. Maintain discharge cleaning for the desired period.

12.

Shut down discharge cleaning. Verify that the Piezo-electric valve has been asked to close.

13.

Evacuate the gas line. (This can be done automatically from the DIBORANE PLC by enabling AUTO and enabling PURGE5.) Begin by closing PV5. Open PV3. Open PV1. Open PV2 until the diborane transducer indicates the line is under vacuum. Close PV2. Open PV4. Cycle PV2 and PV4 every 15 seconds a total of 20 times.

14.

Enter the cell under access control. Don the welding glove and close the valve on the diborane (helium) bottle. Exit the cell, manually set the switch on the PLC which indicates that the diborane bottle valve has been closed and initiate the PURGE60 cycle.

15.

At completion of the purge cycle, shut PV6, PV1, and PV5 and the Piezo-electric valve. PV2, PV3 and PV4 should already be closed. Release the access control system. Close the REG1 regulator and MV1. The discharge cleaning session is now complete.

16.

When the vacuum vessel has been pumped out (1 to 1.6 mTorr on TC3), GV1 may be reopened, and IGT turned on. The diagnostic valves which were closed at the beginning of this procedure may be re-opened. DO NOT OPEN GV3. Turn on the remaining filaments and RGA's.

I.

Training

Those responsible should review these procedures in detail, and should receive training in toxic gas hazards, and SCBA usage.

J.

Summary Check List

1.

Toxic gas monitor function.

a.

Check gas monitor A.

b.

Check gas monitor B.

2.

Vacuum test of system lines

3.

PLC control system function.

a.

Toxic gas monitor fault, at cabinet

b.

Toxic gas monitor fault, B side

c.

Exhaust blower failure

d.

Vent damper closure

e.

House air loss

f.

Vaporizer gas loss

g.

Access system breach

4.

Inert gas system test.

a.

Setup for the test: Install the helium gas bottle in the space provided for the diborane bottle.

b.

Enter the cell under controlled access to perform the next 2 items.

c.

Verify that manual valves MV1 and MV3 are open. Verify that the diborane regulator (REG1) is set to 30 PSI, the venturi regulator (REG3) is set to 100 PSI, and the helium purge gas regulator (REG2) is set to 30 PSI. PV3 and PV4 and manual valve MV2 will have to be open to set the diborane regulator pressure.

d.

Start the flow from the vapor work and the vacuum pump outlet by opening ball valve MV5 and the valve going to the torus roughing pump.

e.

Verify that MV4 is open.

f.

Activate the purge procedure from the PLC. The AUTO switch on the DIBORANE PLC must be enabled. Enable PURGE60. This will not work unless the DIBORANE CLSD bit is enabled. Do not change this bit without verification of the bottle valve status.

g.

Verify that the PURGE60 cycle is working. Make sure that PV5 is open, and that TR4 is cycling between vacuum and pressure.

h.

Two people should enter the cell under controlled access, taking 2 walkie-talkies. One should don the welding glove and open the diborane (helium) bottle while the other watches the toxic gas detector on the cabinet. Enable the DIBORANE OPN bit on the PLC.

i.

Set up for the discharge cleaning cycle. Enable the Diborane on button on the DIBORANE PLC.

j.

Go into the TORVAC PLC. Turn off all filaments specified (IGT, IGP1, IGP2, both RGA's, the Ratiomatic.) Close all of the diagnostic gate valves.

k.

Close GV3. Close GV2. Close GV1. Open SV3. Open SV4 to 100. Open GV2. Turn IGP1 back on. If the pressure on IGP1 is less than 5×10^-5 Torr turn on the Dycor RGA. Go into the AFILL screen of TORVAC and clear the fault, even if no fault is indicated.

l.

Set the pressure by entering a requested pressure into the DIBORANE PLC and enable the fill request. It will ask for a password (FILL) in order to proceed.

m.

Activate the diborane discharge cleaning mode from TORVAC. Verify that a discharge has formed in the machine. Maintain discharge cleaning for 30 minutes to check system function.

n.

Shut down discharge cleaning. Verify that the Piezo-electric valve has been asked to close.

o.

Evacuate the gas line. (This can be done automatically from the DIBORANE PLC by enabling AUTO and enabling PURGE5.) Begin by closing PV5. Open PV3. Open PV1. Open PV2 until the diborane transducer indicates the line is under vacuum. Close PV2. Open PV4. Cycle PV2 and PV4 every 15 seconds a total of 20 times.

p.

Enter the cell under access control. Don the welding glove and close the valve on the diborane (helium) bottle. Exit the cell.

q.

Enable the DIBORANE CLSD switch on the DIBORANE PLC.

r.

Initiate the PURGE60 cycle.

s.

At completion of the purge cycle verify that all automatic valves are shut.

t.

Release the access control system.

u.

Enter the cell and close the REG1 regulator and MV1. The discharge cleaning session is now complete.

v.

When the vacuum vessel has been pumped out (1 to 1.6 mTorr on TC3), GV1 may be reopened, and IGT turned on. The diagnostic valves which were closed at the beginning of this procedure may be re-opened. Turn on the remaining filaments and RGA's.

K.

Cross references

Procedure for Installation of Diborane Gas.

Procedure for Diborane Gas System Discharge Cleaning.

Procedure for Diborane Gas System Maintenance.

Emergency Procedure for Diborane Gas System.

Safety Analysis Report for Diborane Injection in Alcator C-Mod

L.

Distribution

E. Marmar, J. Irby, C. Reddy, R. Clifford, J. Bosco, B. Childs, I. Hutchinson, F. Silva.

M.

References

Matheson gas catalogue.

MDA Scientific `` TLD-1 Toxic Gas Detector Operating Instructions''