Hello I found that uranium glass plate near reactor had increased activity and started to inspect it more closely.
I used SBM-20 geiger tube (tested also sbm-19 but counts up 26000/min, and not sure how well counter can handle so high readings), counter was DYI arduino (from ebay).
test 1., taped SBM-20 to plate center, outside ~25M from reactor counts ~850c/min. (Plate was slight activated, plus uranium beta decay)
Then I put it over reactor, from ~20cm distance core, it is ~19cm air + 1cm lead. Counts grow to 1860c/min.
Then I put canister of water on reactor and top sbm20 plate, extra 20cm distance, water ~11cm. Counts drop to ~1090c/min
Then I remove water canister and used wet towel layered ~1cm thick and sbm20 plate. Counts rise 1920c/min.
--> near thermal neutrons or what?
After I got idea to remove betas and used special (tin?) foil designed/used to remove SBM20 beta sensitivy.
Foil wrapped SBM20 outside far from reactor 20c/min.
Foil wrapped SBM20 taped to glass plate 58c/min. (plate have got some fission products. Normal clean readings should be ~20c/min BG).
And on reactor with wet towel 10min average 127c/min.
After test plate give ~60c/min.
Glass plate have low uranium content maybe 0.5-1%.
Is it posible to aproximate neutron flux from above data?