Development of wood materials as a radon sealant

混凝土和其他无机建筑材料释放出氡，它具有放射性并停留在空气密闭的房间里。据说，人长期生活在氡浓度高的房间里，会受到放射性的影响，有患肺癌的危险。本研究的目的是利用木质材料作为氡密封剂，对无机材料中的氡进行密封。由于氡的半衰变时间很短，只有40分钟，因此预计木材可以降低氡在木材中扩散时的放射性。采用两种方法对木质材料的氡密封胶性能进行了评价。合同方法；将一块氡辐射高的无机材料板作为样品块，与两块木板面对面夹在一起，边缘用胶水密封。在干燥器设置的样品块中，用杯法监测氡浓度。非契约方法；氡浓度在用样品板隔开的室中测量。氡源放置在室的一侧。作为结果，1。氡浓度随样品厚度的增加而降低。从最大还原率到最大还原率依次为软木胶合板、lauan胶合板、刨花板、MDF.2。厚度为2.8mm的中密度纤维板的还原率为17%，而丙烯酸涂层的还原率达到89%。3. 木质材料的氡扩散系数为7-30x10^<-5> cm^2/s。4. 木炭可以减少石膏粉的氡排放。石膏与15%活性炭混合后的氡散发率降至90%，与杉木纤维木炭混合后的氡散发率降至70%。本研究为开发一种具有高性能氡密封胶的新型室内材料提供了可能。现对在此基础上研制的新型石膏板进行性能评价。

Concrete and other inorganic construction materials emanate radon, which has radio-activity and stays in the air tightened room. It is said that people is affected by radioactivity and has a risk of lung cancer when they live in the room of a high radon concentrations for long time.The aim of this research is to seal the radon emanation from inorganic materials by using wooden materials as a radon sealant. It is expected that wooden materials reduce the radioactivity of radon during diffusing through wooden materials, because of its short half decay time of 40 minutes.Two methods were employed to evaluate the performance of radon sealant of wooden materials. A contract method ; As a sample block, an inorganic material board with high radon emanation were sandwiched with two wooden boards, surface to surface, and the edge was sealed with a glue. Radon concentration in a desiccator setting the sample block was monitored with a cup method. A non-contract method ; Radon concentrations was measured in the chambers separated by a sample board. Radon source was put in the one side of the chambers.As the results,1. Radon concentrations was reduced with the increases in the thickness of the sample. The order of the reduction rate from the highest reduction was soft wood plywood, lauan plywood, particle board and MDF.2. The reduction rate of MDF with 2.8mm thickness was 17% but the acrylic coating rose the reduction rate to 89%. 3. The wooden materials gave 7-30x10^<-5> cm^2/s as the diffusion coefficient of radon. 4. Charcoal reduces the radon emanation from the gypsum powder. The radon emanation of gypsum mixed with 15% of activated charcoal was reduced to 90%, and that of the mixture with charcoal of fir fiber was 70%.This study gave a possibility to develop a new interior materials which has high performance of radon sealant. Now we are evaluating the performance of the new gypsum board which was manufactured basing on this research.