Variation characteristics of the radon's concentration and protection to the harm in the Xueyu cave,Chongqing

PRM-2100(Radon RAE Progeny)is used to measure the equivalently effective concentration(EECRn)of radon's daughter in the Xueyu cave for 12months.The average EECRn is 2 135.7Bq/m3.Take the balance factor as 0.5,the average concentration of radon in the Xueyu cave is 4 271.4Bq/m3.The EECRn is higher in summer and lower in winter.The EECRn in each layer is different,the higher the layer,the higher the EECRn.The outside temperature can affect the EECRn 's distribution in cave environment.The effective dose there to tourists is only 0.02mSv/a,only amount to 1.54%of the threshold value(1.30mSv/a) estimated by the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR),so it is unharmful dose to the public and will not affect the health of tourists.The effective dose for tourist guides,security guards and photographer is 7.69mSv/a,11.96mSv/a,59.48mSv/a respectively,which are higher than the UNSCEAR estimated annual effective dose to the public.These effective doses should be received sufficient attention.The protection measures for tourism caves include reasonable arrangement for staff working hours and annual maximum working hours in the cave,popularization the knowledge about radon hazards and enhance the awareness of self-protection for the cave staff.In the high radon concentration area,shield protection or air purifier at appropriate position should be installed,and at the same time the analysis and monitor to the concentration of radon and its progeny should be strengthened.