Radon Hut Mini Status Report, 11 March 2004

HGB, Mozumi/Japan, updated 3/13/2004.

[Note: click on the pictures below to see them full sized.]


SK radon hut & newly finished KamLAND radon hut

New water intake filter and hose installed

Jeff and I installed a new larger water intake filter with checkvalve and flexhose on March 9, 2004. Jeff also added a fine-webbed stainless steel cage underneath the intake filter/checkvalve which keeps the intake steadily in pleace in the water stream about 2" above the rocky ground. It'll prevent rocks and debris larger than 1/4" diameter from entering the pumps.

Please note also the added pipe structure from the new KamLAND fresh air system. KamLAND technicians recently installed a sump pump within approx. 2 feet downstream of our water intake, together with a filter box and bypass pipe as shown in the third photo below.


new water inlet filter

new inlet installed

water pumps overview

ICRR technicians installed a fire alarm system in the hut

Technicians hired by ICRR were busy installing improved fire alarm systems all over the Super-K experiment area, as part of the new safety requirements introduced for ICRR. They also began installing a fire alarm system in the radon hut which will be networked with the Super-K fire alarm system within the next couple of days.

alarm panel in hut extension
new smoke detector
above the blowers
alarm signal & emergency button
inside the hut at main door
alarm bell outside at main door

New air velocity sensor implemented in suktest DAQ

Roy and Hank installed an air velocity sensor at the air duct in the mine before the first branch to the XMASS area. It is now connected to a free input of the custom radonbox & A/D VME card in the OD TEST VME crate, controlled by suktest (sister workstation of the OD-DAQ online machine sukant).

Note: Actually, the originally installed sensor seemed not to be calibrated correctly. It measured approx. 40% more air velocity than the velocity measured in the radon hut, despite the same duct diameter and almost same air temperatures in the ducts. After turning the probe by 180 degrees, the velocity readout decreased, although it was still more than 10% above the value from the radon hut; see plot below. I replaced the whole sensor unit (probe and electronics enclosure) with a spare sensor and this one is much closer to the data in the radon hut, within approx. 5%.

air velocity sensor
velocity data plot with two different sensors

The velocity data is recorded every 10 minutes along with various temperature sensors in and around the SK dome area. See updated weekly plots of a) the raw velocity data (FPM) and b) the converted and temperature-compensated flow volume (cubicmeter-per-minute) below.

For the latter converted plots I'm applying the same temperature-compensation equation than for the airflow data of the sensor in the radon hut, assuming identical temperature dependency behavior of the moving air in the air duct. The data between them seems to be close, but I don't know how accurate either of them are, though. The datasheet claims the sensor has an accuracy of 2% at operating temperatures from 32 F up to 180 F, but I can clearly see a strong temperature dependency in the airflow data from the radon hut where the values are fluctuating from -20% to +50% for temperatures between 50 F and 100 F despite constant airflow provided by the blower. Therefore, to correctly compare the two airflow sensors, we should calibrate them at the same source eventually.

plots for last 24 hoursplots for last 7 days

raw air velocity data (FPM) of last 24 hours

raw air velocity data (FPM) of last 7 days

temperature-compensated air flow (m^3/min) of last 24 hours

temperature-compensated air flow (m^3/min) of last 7 days

Misc. Notes

Jeff and I had a meeting with Nishitani-san, Kiyoko, and a mining company engineer (whose name I forgot) at the Atotsu office on March 10, 2004. We were shown photos and samples of the air duct repair work they did earlier this year. They replaced 10 of the worst leaking duct couplings in the tunnel that I had listed in an excel sheet in September last year and put new couplings with additional waterproof taping. The other 12 problem couplings were also examined and either repaired with old, but good coupling material or left alone where no actual leak was detected. The 90-degree duct section after the outlet filter behind the hut was also fixed and doesn't leak anymore, and same with the follow-up coupling where Roy had drilled a test hold for a flow sensor last summer and patched with tape.

They pointed out that the duct sections in the tunnel have probably straigtened out during the recent cold months and some of the couplings that leaked in September didn't leak in January/February anymore. Most of the problem couplings showed heavy wear on the rubber seals, which came unglued at some sections caused by water in the pipe and high pressure. This wouldn't have happened if the air had been dried (dehumidified) before blown through the duct.


example of leaky coupling

another example

air duct couplings of
SK system vs.
KamLAND system

So, we were asked if it's possible to make the air drier, i.e. adding an active dehumidifier to the system like in our previous setup with the old blowers. Bleeders are simply not enough to get water out of the pipes; need to prevent water from getting into the pipe at first. (Our answer: we would like to, but it'll be very expensive and we'd need to free up a lot of space in the hut to install a suitable heat exchanger). They also mentioned that KamLAND techs had learned from our experiences and therefore added a heat exchanger with dehumidifier at the air inlet in addition to a passive water chiller at the outlet. The design for the KamLAND air duct couplings was also improved with stainless steel clamps and additional tension clamps as a result of observing our problems with the plastic couplings.

Last not least, we requested a cost estimate for adding more support brackets along the first ~500 meters of the tunnel to straighten the air duct as good as possible and prevent further bending even if condensation water is collecing inside. They'll also let us know soon how much it'll cost to upgrade all ~120 duct couplings at the first 500 meters with improved rubber seals and additional waterproof tape. A complete coupling clamp set costs approx. 6,000 JPY per coupling. They'll check if its possible just to replace the rubber seals but re-use the actual PVC parts in order to save costs.