The Spallation Neutron Source has continued to operate at reduced power in recent months while waiting on additional target vessels (there were two vessel failures last fall) to arrive, but the recent operations at SNS have reportedly been good — actually better than good, according to division director Kevin Jones.
“SNS is operating at 850 kW this week, as it has been since we resumed operation in mid-January,” Jones said in an email response to questions. ” We just reported our performance for the January-March quarter to the Department of Energy, and I’m pleased to tell you that our beam availability against schedule for this period was 94%. Just last week we had our first-ever week with beam availability of over 99% (less than one hour of down time for 159 hours of operation).”
More good news: Jones said a newly manufactured target vessel arrived on Thursday, and there are high expectations for future operations. Much effort is being expended to better understand what caused the premature failures last fall and two years ago and to avert them in the future.
“This is a standard mercury flow target, but incorporates two important design changes,” he said. “One design change eliminates the trapezoidal plate that was the location of three of the last four leaks. That component is now machined from a single piece of metal stock.”
The other design change is the “bolt-on water shroud, that will now be standard on all targets we receive,” Jones stated. “This greatly facilitates our ability to do post-irradiation examination (after the vessel has been removed from the target location).”
Besides that, the ORNL team has decided to put in place some additional instruments on the new target to try to get more data on the “structural response” of the vessel after it is put into place and receives its first pounding from the proton beam.
“Specifically, we added 8 very small fiber-optic-based strain gauges at strategic locations on the mercury vessel of the target assembly, and have designed the systems necessary to get data from these strain gauges when this target is installed and first exposed to single beam pulses,” Jones said. “Should this work, we will get very valuable data on strain and deformation that will validate our computational models. These data would be obtained when the target is placed in service.”
The SNS team hasn’t yet ramped up the power level (which means more neutrons for experiments), but that’s coming later this month.
“Next week we will be off for a short scheduled maintenance period, during which we will reconfigure the accelerator to support higher power operation,” Jones said. ” When we decided last fall to run at 850 kW we made some adjustments to reduce our overall power consumption and hence reduce utility costs. We will also undertake some tasks intended to ensure that we can operate well at higher power.”
After the brief pause, the plan is to restart the SNS systems on April 18 and resume neutron production three days later, the ORNL official said.
“Our intention is to run above 1 MW on target, with a goal of about 1.2-1.25 MW for sustained operation not too long after we resume neutron production,” he said.
“If the current target operates well at the increased power level we anticipate that the next scheduled target replacement would occur in early October 2015.”
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