New air intake system for the radon hut

1. Old air intake system [before the change]
2. After installation 9/4/97
3. Completed installation after 11/25/97

Air inlet at the power pole behind the hut:

Originally, Peter had left the extended air inlet unhooked since it was at about the same horizontal level as the kerosine heater's exhaust pipe. Thus, the incoming air was not quite clean and even had a good level of CO concentrations. Since I was checking the system in bypass and "filter-without-regeneration" mode I decided it would be better to reconnect the extension to the lower air inlet. This way the inlet is moved approx. 4 meters further up (approx. 6 meters above street level) and therefore most likely contains a lower radon concentration from the tunnel airflow.

Service blower air filter inside the "vacuum" chamber:

(Already indicating problems with the installation of the new aluminum boxes: The 4.5" pipe studs are too short and blocked by a 3.5" wide 4.8" diameter coupler. Latter one is tightly mounted, not removable with standard equipment...)

New filter box for one of the blower air filters (before installation):

[Actually, this box turned out to be too large to fit over the service blower's intake filter. It needed a redesign (see suggested changes) which was finished by Butch Juds (UCI) in October 97.]

8" to 2 x 6" inlet box at rear hut wall (outside view):

The 8" opening will be hooked up with a flexible hose to a new air intake location up the hill as soon as there is an agreement with the owner of the property.

8" to 2 x 6" inlet box at rear hut wall (inside view):

The 6" regeneration outlet is currently sealed with a pipe stud terminated with a silicone embedded piece of insulation material. Three environment sensors are mounted on the rear side: CO_A (carbon monoxide sensor), TA (temperature), and RHA (relative humidity).

Box over service blower air filter now completely assembled:

In order to fit the new box (too large) onto the filter.muffler unit of the service blower it had to be jacked up for about 3 inches. That's why it appears to be at an angle in the picture above. It now sits tightly positioned just above the rear section of the regeneration blower, and thereby blocking a lubrication port of the regen. blower.

Completed installation after 11/25/97

Filter housing uphill:

This is the new air intake filter housing, mouted uphill in the forest behind the radon hut, approx. 20-25 meters above ground level at the tunnel entrance. It has a little roof to protect the air inlet from direct rain or snow fall and its walls are made of mesh wire to filter falling leaves, forest debris and midsize to large insects. The housing is connected to the radon hut with a 35 meter 8" flexible rubber/plasic hose. The hose might need to be replaced with a sturdy, weather-protected pipe during next spring or summer.

New, smaller box over service blower air filter:

This picture shows the new, smaller filter box mounted at the muffler input of the service blower. The original blue vacuum lid of the fine-filter has been removed so that the incoming airflow is more directly going through the fine filter. A clear plexiglass window helps the maintenance person to quickly check whether the fine filter needs to be replaced soon or not.

Radon monitor data after the first 7 days of operation with the new extended air intake:

The following histograms were plotted with the RNHIST (radon monitor histogram) software at sukslc. The base of the x-axis of all 4 plots is time in days over the 7-day period from 11/26 ... 12/03/97. The y-axis each represent (from top to bottom):

1. "SKDomeAir": Radon monitor (Bq/m³) in the SuperK dome air,
2. "DuctAir": Radon monitor (Bq/m³) in the air duct in the SK dome; i.e. air coming from the radon hut,
3. "MineAir": Radon monitor (Bq/m³) in the mining tunnel outside the SK dome, measured near the SK water purification system,
4. "TA": Temperature (° Celsius) of the ambient (intake) air at the radon hut.

Coincidently during this 7-day period the weather turned out to be unusually warm for a typical end-of-November pattern in the Mozumi area. As shown in the "MineAir" plot, the radon level inside the mine jumped to high levels above 500 Bq/m³ when the outside air temperature was somewhat above 12-13 ° Celsius (as shown in the "TA" plot).

The "DuctAir" plot shows that the radon level of the air delivered by the radon system stayed below 40 Bq/m³ levels during the whole time, averaging at about 15-20 Bq/m³. This is as predicted from the radon surveys in the summer!! Thus, no more feedback effects from radon-rich air blowing out of the mine tunnel back into the radon system as observed before the extended intake installation.
[I'll be preparing a similar plot of earlier data as soon as I have figured out how to retrieve it from sukslc. This will show the feedback effect before the extended air intake installation.]

Even though the air delivered by the radon system was kept at very low radon levels, it appears in the "SKDomeAir" plot that the radon levels inside the dome started rising up to almost 300 Bq/m³ soon after the mine air levels reached its first peak (in the night from day 1 to day 2). It looks like it then took until the end of day 3 to get this level below 100 Bq/m³ again!

The only possible explanation for this effect: During days 1 and 2 there were a lot of LINAC calibration activities scheduled inside the dome. During the LINAC pipe setups the doors to the LINAC cave and to the dome entrance were opened several times for longer duration. This must have allowed radon-rich air to get into the dome and mix with the clean air coming from the radon hut.

Only solution I can think of right now: As Peter already suggested earlier, the doors and all other gaps to the SK dome need to be sealed where radon-rich mine air can sneak in!!

If it is still desired to reach even much lower radon levels than 30 Bq/m³ then regular regeneration of the carbon filters might help. But before spending all the money for a fully-function regeneration system I suggest to spend it on the complete sealing of the SK dome first! Otherwise that money is going to be burned away for nothing, literally...