Survey for cleaner air intake locations for the Radon hut

Why a new intake location?

During the warmer season when the air inside the mine is cooler than the outside air, the air is blowing from the mine to the outside. Whenever this happens the radon concentration of the air inside the mine, including the SuperK tank, can reach high levels in the range of 40...70 pCi/l. Radon concentrations above 4 pCi/l are considered health risky. Also, it is suspected that higher concentrations might add as noise background to the SuperK PMT data.

The "Radon-free Air Supply" system in the radon hut was constructed to deliver fresh, radon-poor (filtered) air to the SuperK dome and its adjacent control room. Unfortunately, it is positioned at almost the worst possible location near the tunnel entrance. The following pictures were taken during a humid day in July 1997 when the condensation effect of the cool tunnel air mixing with the outside air is highly visible.

* Photographed from the Atotsu building entrance. Here, the cool tunnel air moves from left to right (from the tunnel over the street into the valley). The radon hut is sitting right in its path!

* A different point of view, right next to the Atotsu office building on the access road to route 41. The fog is moving from left to right. The radon hut behind it, right next to the transformer power pole in the background.

* Here a picture of the valley with the river near the big parking lot behind the Atotsu office building. The fog is creeping downhill into the river.

Thus, in order to avoid radon-enriched air feeding back through the radon hut's system a new air intake location away from the hut is desired.

Location 1: 20 m uphill behind the radon hut

Results from electronic radon monitor measurements: In average about factor 6 ... 7 better than at the current radon hut air intake

Lab test result from the radon test kit deployed from July 18 ... 26, 1997: average = 0.5 pCi/l.

Location 2: 10 m uphill above the tunnel entrance

(this is an archived picture of the tunnel entrance at a typical winter day)

Rn survey location 2

Results from two electronic radon monitor measurements: In average approx. faxtor 4 ... 5 better than at the reference location.

Lab test result from the radon test kit deployed from July 18 ... 26, 1997: average = 1.9 pCi/l.

Location 3: corner of the big parking lot near the river

(No electronic measurements)

Lab test result from the radon test kit deployed from July 18 ... 26, 1997: average = 1.8 pCi/l.

Location 4: reference location at the hut (current air intake)

Lab test result from the radon test kit deployed from July 18 ... 26, 1997: average = 10.2 pCi/l.

Location 5: near CO monitor in the tunnel entrance

Results from electronic radon monitor measurements: About factor 5 ... 7 worse than at the reference location!

Location 6: behind the Atotsu office building

Results from electronic radon monitor measurements: In average about the same Rn concentrations as at the radon hut!

HGB, 09/05/97

*	Photographed from the Atotsu building entrance. Here, the cool tunnel air moves from left to right (from the tunnel over the street into the valley). The radon hut is sitting right in its path!
*	A different point of view, right next to the Atotsu office building on the access road to route 41. The fog is moving from left to right. The radon hut behind it, right next to the transformer power pole in the background.
*	Here a picture of the valley with the river near the big parking lot behind the Atotsu office building. The fog is creeping downhill into the river.