Response to “MERIT mercury loop safety” review (EDMS 754444)

1.      The request is acknowledge. The base plate will be fixed to the floor. However, it is noted, that the mercury loop is fixed in lateral position with respect to the base plate, whereas the vertical fixation is by gravity only. The solenoid is fixed both laterally and vertically with respect to the base plate.

2.       MIT test in March 2007 have proven, that such movements have not been detected. No efforts were made at MIT to specifically restrain the nose within the solenoid bore, but that option is still available during commissioning tests at CERN.

3.   Modifications of the hydraulic pump setup are scheduled.

4.        The procurement specification was added to the Appendix of the MERIT Design Ops Report and is also contained in "203-HJT-9000R1b Pump Spec Final.pdf". Pressure test data of the syringe cylinders is in the Appendix of the MERIT Design Ops Report.

5.   Information is provided in file "Hanna Mounting Bolts 706-81637-002".

6.         The term "critical" referred to control system functionality, and these were considered separately from safety sensors. Cylinder position, for instance, is a sensor which is critical for system operation and is redundant. The operational recommendations regarding safety sensors are noted.

7.         The mercury loop provides a pressure release valve, where the exhaust is directed through a filter system (double staged). System schematic is included within the Hg loop installation manual along with detailed procedures for each operation.

8.        The only liquid check valve in the system is between the sump tank and the Hg cylinder and prevents Hg from returning to the sump tank during a jet formation. This check valve is a passive component with no remote readout capability.

9.         The material list is fully compatible with the CERN safety policy and the use of mercury. Cables of the SCEM 04.21.52.140.4 and 04.21.52.100.2, which are in accordance with safety instructions IS 23, are used for wiring inside the secondary box and for the umbilicals between the secondary box and the hydraulic power unit. A list of non-metallic materials used in the Hg system is found in "Flammable Materials List 29Mar07".

10.      The base plate sliding surfaces are fabricated from ultra-high-molecular-weight polyethylene, which does not contain halogenated materials. The sole use of non-compatible material is the LEXAN cover. See below.

11.      The LEXAN cover could be replaced, if the fire scenario would require it. There are no Lexan windows in use with the view ports.

12.     A list of non-metallic materials used in the Hg system is found in "Flammable Materials List 29Mar07".

13.   Leak testing procedures were developed and demonstrated at ORNL and have been included in the system Operating manual. See presentation on MIT test of March 2007.

14.     The MERIT collaboration acknowledges the request and will act accordingly.  V. Graves and A. Carroll will be at CERN for pre-ops testing, and for Hg filling and draining. Either will be at CERN during test operations. Their qualifications are attested in writing to CERN, by the NSTD Safety Officer , or his designee. Contact information will be made available to CERN and a placard will be placed on the MERIT equipment.

15.     See presentation on MIT test of March 2007.

16.     The MERIT collaboration acknowledges the request and will act accordingly.

17.     See Installation Manual R1 (previous version).

18.     See Hg loop operation manual and presentation on MIT tests of March 2007.

19.    The MERIT collaboration uses two different Hg vapor monitor systems. See also on MIT test of March 2007.

20.   The main indicator for Hg release is not an absolute reading, more the sudden change of mercury concentration. See movie on mercury reading at MIT. Higher mercury concentrations can be removed like the case of filling and drainage. A hazard with mercury loss to the secondary containment has to be treated accordingly. A small (~20mL) Hg leak was experienced at ORNL which caused Hg vapor levels to approach exceed 1 mg/m3 inside the secondary containment; no Hg vapors were detected outside the secondary. The alarm threshold inside the secondary will be increased as there were no detrimental effects to the equipment or escape of vapors from the system.

21.     Acknowledged. See also above.

22.   To be done. We expect negligible doses, as the overall activation is small, mercury is self-shielding and the access times to highly irradiated items are not expected to be long.

23.   See logbook of filling and draining (MIT test). Procedures for filling and draining Hg are included in the Hg loop installation manual. Hg will be transported in eleven separate flasks, so partial filling or draining will not cause any operational concerns. The actual amount filled at CERN has been reduced to 60% of the initial total of 23 liter.

24.   Emergency stop actuators are placed in the vicinity of the experimental setup. An emergency stop in the control room is not yet provided, as the experimental cycle of a few seconds is comparably short to any human intervention.

25.   In accordance with the shipping group and the safety group at CERN, the transport has passed successfully. For shipping back to the US, it is envisaged the wait for a year-long cool-down period, such that the material can be transported as low-radioactive classified on the same way as coming to CERN. The material of the mercury loop will as well be classified as "mercury wet".

26.   See 3rd safety review of 30th March 2007.

27. The MERIT collaboration is now providing as much information following the successful tests performed at the beginning of March 2007. This tests were performed later than originally expected.