| Radon is a natural radiation source widespread in nature. If the human body inhalation high concentrations of radon for a long time, the probability of falling in lung cancer and other diseases will be increased. Tourist cave is a relatively closed or semi-closed space, the internal temperature change is small, easy to accumulate high concentrations of radon. With a large number of caves are developed for touring, more and more tourists and cave staff are faced with increasing health risks. Xueyu Cave is the most youngest developed tourist caves in China, and was named "one of the most beautiful tourist caves". Xueyu Cave has extremely high ornamental value and scientific research value, attracting a large number of tourists. This paper takes Xueyu cave as a case study, periodic monitoring the concentration of radon and its progeny, explores EECRn’s variation law in different climatic conditions and different measurement points. Based on the research results about other show caves at home and abroad, formulates working time limit to staff in Xueyu cave, provides a reference to managers in Xueyu cave, and protects the health of the staff; at the same time, provides a reference for other tourist cave.In this research, literature research method, quantitative analysis method, field survey, monitoring and other research methods are used. The author regular and continuous monitoring the concentration of radon and its daughters in Xueyu cave from April2012to March2013, Conclusions are as follows:1. Through12months’consecutive monitoring the concentration of radon and its daughters in Xueyu cave, we found that the average EECRn is2135.7Bq/m’, which is significantly higher than radon concentration limits (1500Bq/m3EECRn) stipulated by national standards for mine staff. Take the balance factor as0.5, Xueyu cave’s average EECRn is4271.4Bq/m3from April2012to March2013, far higher than the International Commission on Radiological Protection (ICRP) Publication No.65provision the residential radon concentration within the action levels(200～600Bq/m3) and workplace action level (500～1500Bq/m3), is3.88times of the ordinary radioactive workplace maximum limit (1100Bq/m3) which was stipulated by China, and is66times the average radon concentration in the indoor air in the main city of Chongqing (64.5Bq/m3). Compared with part of the concentrations of radon in domestic caves, Xueyu cave is the highest concentrations of radon in tourist caves.2. The EECRn is high in summer and low in winter, no significant difference between spring and autumn in Xueyu cave, and summer’s EECRn is16times than winter. EECRn is gradually increased from low, from high to low and then increased gradually and then reduce just as "M"-shaped in Xueyu cave. EECRn in each layer is different, the higher the layer, the higher the radon concentration. The outside temperature can affect the EECRn’ distribution in tourist caves.3. The effective dose for tourists is only0.02mSv/a, which is1.54%to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimates the annual effective dose to the public(1.30mSv/a), and is1.55%to2.86%to Chongqing’s indoor and outdoor environment accounted value(0.70～1.29mSv/a). This effective dose will not affect the health of tourists. The effective dose fo tour guides is7.69mSv/a, which is5.92times to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimates the annual effective dose to the public(1.30mSv/a), and at least5.96times to Chongqing’s indoor and outdoor environment accounted value(0.70～1.29mSv/a). The effective dose for security guards is11.96mSv/a, which is9.2times to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimates the annual effective dose to the public(1.30mSv/a), and at least9.27times to Chongqing’s indoor and outdoor environment accounted value(0.70～1.29mSv/a). The effective dose for photographer in Xueyu Cave is59.48mSv/a, which is45.75times to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimates the annual effective dose to the public(1.30mSv/a), and at least46.11times to Chongqing’s indoor and outdoor environment accounted value(0.70～1.29mSv/a). This effective dose requires sufficient attention.4. The radon protection measures for tourist caves including:reasonable arrangement for staff working hours within the cave, draw up annual maximum working hours, popularize the knowledge on radon hazards and caves staff’s self-protection, take shield protection in the area of high radon concentration, instal air purifier at appropriate position, strengthen the analysis and monitoring to the concentration of radon and its progeny. |
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