1. RELIABILITY OF JAPAN PROTON ACCELERATOR RESEARCH COMPLEX
K. Yamamoto#, K. Hasegawa, M. Kinsho, H. Oguri, N. Hayashi, Y. Yamazaki and K. Kikuchi
JAEA/J-PARC, Tokai-mura, Japan
F. Naito, T. Koseki, N. Yamamoto, M. Yoshii and Y. Hori, KEK/J-PARC, Tokai-mura, Japan #
Intro
The Japan Proton Accelerator Research Complex (J-PARC) is a multipurpose facility for scientific experiments.
J-PARC consists of three accelerators and three experimental facilities. The user operation began in December 2008.
We continued the operation but encountered some accidental suspensions. We describe the major incidents and metrics.
Operation status of J-PARC
Neutron target failures
RCS-BM oil pump failure
SX septum failure
Water leak of MR-inj septum
Linac HVTR failure
Neutron target failures
RCS-BM oil pump failure
SX septum failure
Water leak of MR-inj septum
Linac HVTR failure
MTBF is dominated by the condition of RFQ
Only NU operation : low duty
Seemed to be gradually improved
300 kW
200 kW
500 kW -> Neutron target failures
100 kW
Old RFQ
After N-target failures, beam power was restricted less than 200 kW
New RFQ
20 kW
Earthquake
Radiation accident of Hadron facility
RFQ contaminated by the vacuum leak due to the earthquake
Mean Time to Repair
Availability
Acceleration particles in RCS
Mean Time Between Failure
Operation status before the 2011 earthquake
Operation of 2011 – 2012; Tohoku Region Pacific Coast Earthquake and HVTR failure
Discharge of the thyratron in RCS extraction kicker magnet system
HVTR failure and replacement
Magnet displacement in linac
discharge of the RFQ
See Thursday evening session
“Effort for the Reliable Operation in J-PARC Rapid Cycling Synchrotron”
CX1193C
by TELEDYNE e2v Ltd.
The facilities of J-PARC were seriously damaged by the March 11 earthquake.
Completed the recovery work in nine months.
A high voltage transformer (HVTR) of the klystron power supply #1 was disabled.
Approximately 10 days for replacement work.
Cause of low availability in this period:
discharge of the Radio Frequency Quadrupole linac (RFQ) and the thyratron
degradation of the finemet cores in the ring (RCS and MR) RF cavity
Core buckling of RF cavity in RCS
Operation of 2013 – 2014; Troubles related with SX beam extraction
Operation of 2015; Neutron target failures and decrease of flow rate in linac cooling water
system
Distortion of SX septum plate
The neutron target of the MLF was broken twice during the operation of the 500 kW beam and the cooling water leaked.
Radioactive material leak at the Hadron Experimental Facility
Mercury target
Mon201
Mon202
Plate distortion
Outer shroud wall
Inner shroud wall
Mercury vessel
Bolt
Diffusion bonded surface
Seal welding
Water
Helium
Exhaust by air fans
Air conditioning fans
Mon203
Rad-monitors
The beam spot of the gold target heated up and the gold target sublimed.
Water drop
The proton beam was extracted within much shorter time than in normal operations.
The SX septum broke before the HD accident.
Resulted in an unscheduled 3-day shutdown and the switching of the beam mode from SX to FX.
Decrease in the cooling water flow of linac contributed to the downtime. We adjusted the cooling-water-flow rates at the weekly scheduled maintenance, but some flow rates still dropped unexpectedly. Finally we installed additional valves.
Part of the gold target sublimed and absorbed on the vacuum window
Operation of 2016; Many troubles
Status of this year
Vacuum leak
A similar event was reported at CERN during the same time period
Breakdown of helium compressor
short circuit by water leak
Wires snapping of SX septum
A helium compressor at the neutrino beam line produced trouble
The user operation suspended for about two weeks
One of the electro-static septum of the SX failed
We coped with this issue for about three weeks
We encountered one obstacle after another in 2016.
The RCS collimators was broken.
Three troubles by the noise in MR (vacuum leak due to strike the miss-kicked beam, the initial failure of the new injection-septum power supply, overheating of the transformer in the anode power supply of the RF cavity)
Two large short circuits in MR (at the coil of the BM and at the new transformer in the injection-septum magnet.)
Snapping of wires
No protection cover for small animal
Secondary cooling water
Primary cooling water
Cooling water pump trouble in Linac
Heat exchanger
Purifier
Deaerator
Boilers
A new, additional water cooling pump had been prepared during the previous summer shutdown
But it was failed in Feb.
Separated this failed pump from the cooling-water system and operation restarted the next day
Some cooling pipes were clogged with iron particles
Impeller scraped them from the casing
Removed these particles in every maintenance period
Large noise
No noise
Temp.
Control
tank
Pump (old)
Valve
Before improvement
After
Boiler
Open
Initial charging circuit works just
3 minutes.
However, not turned off by the noise.
Finally transformer was overheated.
Close
Adjuster
Accelerator
components
3 IGBTs were broken
Failure
cooling pipes were clogged with iron particles
Pump (new)
Discussion and Summary
In the eleven years since the start of the beam commissioning, Troubles due to system aging have increased. Some spare parts have become obsolete, and we cannot obtain similar new ones. Even though the manufacturer guaranteed backward compatibility, many troubles have resulted from the new system.
When we install a new system, we have to pay very close attention after installation. Even if we check the stability by continuous operation for about a week in a factory or laboratory, problems often arise after installation. Thus long-term monitoring is also necessary.
After the Fukushima Daiichi nuclear disaster, surrounding residents have been nervous about any incident at the radiation facility. J-PARC caused a radioactive material leak accident at Hadron Facility and all facilities were shut down for 9 months. Even if it is not a radiation related accident, any minor incident in the facility that handles radiation is strictly blamed. Therefore, in order to achieve high availability, the accelerator operation must be carried out with utmost safety.