At current location just behind the hut:	10.2 pCi/liter
Approx. 20 m uphill behind the hut:	0.5 pCi/liter
Approx. 10 m uphill above tunnel entrance:	1.9 pCi/liter
At the big parking lot near the river:	1.8 pCi/liter
In the tunnel, just behind the entrance gate:	70.0 pCi/liter ()*
East side of the Atotsu (?) office building:	6.9 pCi/liter ()*

Radon-Free Air System Report

Hans Berns, UW (and UC/I)
11/22/97

Status Report

The "Radon-free Air Supply System" in the "Radon hut" is fully functioning (in "bypass" and "filter-without-regeneration" mode).
Under full-power conditions the service blower can deliver up to 10 m³/min air into the pipe to the SK dome.

"filter-without-regeneration" mode: 10.0 m³/min

"bypass" mode: 9.0 m³/min

"filter-with-regeneration" mode: 9.6 m³/min (heat cycle)

4.8 m³/min (cool cycle)
In all modes - except "filter-with-regeneration" mode - it can run unsupervised, but it should be physically checked by a shift person at least once every 24 hours.
[Maybe day shift only.]
Regular maintenance is needed for the service blower (oil change + grease every 40 days) and other sections of the system (water ok?, filters clean?, etc.). This was previously performed by an employee of the mining company who no longer works there.
We should arrange for a replacement a.s.a.p.!
The "filter-with-regeneration" mode should for now only be enabled if it is possible to babysit the system around the clock - especially during regeneration cycles (approx. every 8-12 hours with a duration of approx. 4 hours).
An expert (Hans or Tomasz) should be available on site as well.
Now installing an air intake extension into forest above the hut to access cleaner air away from mine entrance. With the new intake in place expect much cleaner air (in the summer approx. factor 10-20 better than the current location), the need for further radon-filtering might be obsolete - unless radon levels much lower than 2 pCi/liter are desired.

Why is the system needed?

see http://mochi/~berns/SUPERK/RADON/rnlogs.html

Accomplishments during the summer:

Surveyed the air quality around the hut in July (during the hot summer days) to find a better location for a radon-cleaner air intake.
see http://mochi/~berns/SUPERK/RADON/rnsurvey.html
Results over 7-day period in July 1997:

At current location just behind the hut: 10.2 pCi/liter

Approx. 20 m uphill behind the hut: 0.5 pCi/liter

Approx. 10 m uphill above tunnel entrance: 1.9 pCi/liter

At the big parking lot near the river: 1.8 pCi/liter

In the tunnel, just behind the entrance gate: 70.0 pCi/liter (*)

East side of the Atotsu (?) office building: 6.9 pCi/liter (*)

(*) different time period and different sensor.
[1 pCi/liter = ~37 Bq/m³; 4 pCi/liter or lower is considered free of health risk]

The desired new location will be uphill, at least 20 meters behind the hut, preferably 40 meters (i.e. 20-25 meters above tunnel entrance level). It also has the advantage of being the closest alternative location to the hut, keeping the additional pipes or hoses economically short.

With the help of Miss Yoko Koshizawa we got permission of the land owner to use the desired piece of land for our purpose.
Fixed the cooling water supply (from the tunnel water stream) to prevent water pressure disruption causing the pump to shut down the system.
Especially when the system was turned off for more than 2 hours it used to be a complicated procedure to get it back online again - mostly only with expert help.
Fixed various problems in the heat exchanger unit (needed for de-humidifying the processed air to prevent condensation water from clogging the supplying pipe in the tunnel).
Improved the command+control line quality to/from the control room (9600 baud serial connection). Now about 99.9% noise free.
Mounted electronics in the hut into a rack to make a little more space for the expert. Also, the GPS receiver was moved down from the attic into the electronics rack for much easier access.
see also http://mochi/~berns/SUPERK/RADON/PICS/elecrack.jpg
Relaxed alarm levels in the control software:
- Now allow higher sensor tolerances at non-critical positions.
- Except in "filter-with-regeneration" mode, the system can now be fully controlled remotely from the control room (sukwat console), including turning off (by typing "stop" or "q") and back on (by typing "start").
- Also, except in "filter-with-regeneration" mode, the requirement to push the START button is changed from the previous 8 hour span to a 24 hour span.
  [Note: After the START button has been pushed and the system is running fine the software will wait for 6 hours before it warns the user to push the START button again. Then, if the button hasn't been pushed within the next 24 hours it will shut down the system.]
Started installing an improved sealed air intake system at the service blower. This will prevent radon-rich tunnel air from sneaking into the air intake during warm weather periods.
see also http://mochi/~berns/SUPERK/RADON/newintake.html
The actual air intake opening will soon be relocated away from the hut to a radon-clean position approx. 40 meters away from the hill, and about 20 meters above the tunnel level.
[A filter housing for forest debris and large insects is already installed. Help needed for moving the 8" flexible hoses up the hill to get it connected with the vacuum system in the hut. Need to finish this job early next week, before snow.]

Remaining problems and improvement needs:

The CO sensors used now are not very accurate. They're reliable enough to shut down the system in case of a sudden rise in CO levels, but their absolute readings fluctuate -30 ... +30 ppm, even if the air is completely free of CO.
The temperature inside the hut can reach 40 deg C in the summer, which can cause the water pump and compressor in the heat exchanger to overheat. Excessive heat is not good for the blower engine and the control computer (inside the control panel), either!
Recommendation: Air conditioner or other method of cooling the hut! Without additional cooling in the hot summer days, the "filter-with-regeneration" mode is not possible without constant supervision and the door completely open.
On rare occasions, electrical noise causes some of the electronic sensors to give false alarms and the control software shuts down the system. Some rewiring of critical cables and additional AC power conditioning might improve stability.
If the "regeneration" mode is still desired, then major upgrades will be needed for safety and reliability of the system. E.g. thermal insulation of the carbon tanks and the heater tank.
[Insulating fiberglass wool is already on hand, but a couple of helpers (small, slim persons if possible) are needed to fit the sheets into the tight spaces around the tanks.]

HGB, Nov. 22, 1997

"filter-without-regeneration" mode:	10.0 m³/min
"bypass" mode:	9.0 m³/min
"filter-with-regeneration" mode:	9.6 m³/min (heat cycle)
"filter-with-regeneration" mode:	4.8 m³/min (cool cycle)