When self-disposing of radioactive waste, it is important to follow the acceptable concentration standards for each nuclide set by the Nuclear Safety and Security Commission (NSSC). Gamma-emitting nuclides can be easily analyzed with a simple pretreatment process, but beta-emitting nuclides require a chemical separation procedure to be analyzed for radiochemistry analysis. When analyzing betaemitting nuclides for the purpose of self-disposal, there may be difficulties in radiation detection after the chemical separation process. This is because the concentration of beta nuclides in the sample may be low and some of them may be lost during the chemical separation. Therefore, measurement method of gross-beta activity can be used instead of that of each nuclide to access the compliance of selfdisposal criteria. While a proportional counter is commonly used to measure gross-beta activity, liquid scintillation counting can also be used to measure gross-beta, and we plan to compare the results of both methods.

Level measurement of liquid radwaste is essential for inventory management of treatment system. Among various methods, level measurement based on differential pressure has many advantages. First, it is possible to measure the liquid level of the system regardless of liquid type. Second, as the instrument doesn’t need to be installed near the tank, there is no need to contact the tank when managing it. Therefore, workers’ radiation dose from the system can be decreased. Finally, although it depends on the accuracy, the price of the instrument is relatively low. With these advantages, in general, liquid radwaste level in a tank is measured using differential pressure in the treatment system. Not only the advantages described above, there are some disadvantages. As the liquid in the system is waste, it is not pure but has some suspended materials. These materials can be accumulated in tanks and pipes where the liquids move to come into direct contact with pneumatic pipes that are essential in differential pressure instruments. As a result, in case of a treatment using heat source, the accumulated materials may become sludge causing interference in pneumatic pipes. And this can change the pressure which also affects the level measured. In conclusion, in case of liquid storage tanks in which the situation cannot be checked, the proficiency of an operator becomes important.

In this paper, a low-cost dynamic measurement system using the RGB-depth camera, Microsoft Kinect® v2, is proposed for measuring time-varying free surface motion of liquid dampers used in building vibration mitigation. Various experimental studies are conducted consecutively: performance evaluation and validation of the Kinect® v2, real-time monitoring using the Kinect® v2 SDK(software development kits), point cloud acquisition of liquid free surface in the 3D space, comparison with the existing video sensing technology. Utilizing the proposed Kinect® v2-based measurement system in this study, dynamic behavior of liquid in a laboratory-scaled small tank under a wide frequency range of input excitation is experimentally analyzed.

슬로싱과 같은 액체의 동적 거동을 측정하고 제어하는 연구가 다양한 공학분야에서 활발히 진행중이다. 건축공학분야에서 도 건축물의 풍진동을 저감시키는 동조액체감쇠기의 연구에 액제 진동이 측정되고 있다. 본 논문에서는 기존 파고 측정 센서의 한계를 극복하기 위하여 레이저 장비 중 LDV와 스캐닝 장비 중 갈바노미터스캐너를 이용하여 동조액체감쇠기 내의 액체 진동을 측정하는 방법을 제안하고 검증하였다. LDV가 속도와 변위를 측정하는 원리를 기술하였고 갈바노미터스캐너의 구동 원리에 따라 LDV의 단일 포인트로 다점측정이 가능한 시스템을 구성하였다. 동조 액체감쇠기의 4점 액체 진동을 측정하여 각 점의 시간 영역 데이터를 기존에 사용하던 비디오 센싱 데이터와 비교하였고 파형 분석을 통해 진행파와 정상파를 구별할 수 있음을 확인하였다. 또한 측정 딜레이가 있는 데이터를 상호 상관을 취하여 특이값 분해를 하고 이론 및 비디오 센싱 결과와 일치하는 고유진동수와 모드형상을 도출하였다.

In this study, dynamic vertical displacement of liquid in the tuned liquid column damper(TLCD) is measured by a laser Doppler vibrometer(LDV) to overcome limitations of existing sensors and to leverage noncontact sensing. Addressing advantages of noncontact measurements, operational principles of the LDV to measure velocity and displacement of a target object in motion is explained. The feasibility of application of the LDV to measurement of liquid motion in the TLCD is experimentally explored. A series of shake table tests with the TLCD are performed to determine requirements of application of the LDV. Based on the experimental results, it is proved that the LDV works under the condition of adding dye to the liquid by increasing the intensity of reflected laser and thus validity is verified by comparison with a conventional wave height meter.

A dynamic tube pressure method was proposed for a liquid level measurement. The reliability of our in-house manufactured prototype level measurement system was investigated for water samples in a vial as a preliminary study. The prototype instrument, equipped with a stepper motor and a differential pressure sensor, was used to measure the travel distance of the tube from an initial zero position to the liquid surface. Unlike a conventional bubbler method, our dynamic tube pressure method is based on the abrupt changes in the tube pressure to directly detect the liquid surface. Optimum conditions were determined from the measurements of the travel distance with different-sized tubes at various ambient base pressures and various descending tube speeds. In addition, we proposed a gravimetric calibration method. In the gravimetric calibration method, the travel distances are used instead of the liquid level, which can be obtained from the measurement data of the travel distance. The travel distance versus the weight calibration curve showed a good linear relationship (R2 = 0.9999), and standard deviations of the travel distance over the whole range of experimental conditions were less than 0.1 mm. In a further study, our present system will also be used in the measurement of density and surface tension by minimizing the contact time with high-temperature and highly-corrosive molten salts.

막증류(membrane distillation, MD)용 분리막의 장기 내구성능에 영향을 미치는 인자인 소수성 분리막의 젖음 현상에 대한 평가 지표로 사용되는 액체투과압력(liquid entry pressure, LEP) 측정 방법을 최적화하였다. PE (polyethylene) 분리막 및 PVDF (polyvinylidene di-fluoride) 중공사 분리막의 LEP를 측정하기 위하여 20 wt%의 고농도 염수를 제조하여 원수로 사용하고 투과수의 전도도를 모니터링하였다. PE와 PVDF 중공사 분리막의 신뢰성 있는 LEP 측정을 위해서는 5 min 이상의 holing time을 두고 주입 압력을 증가시켜야 하며, 증류수 수조의 물량대비 분리막의 면적비 또한 10 m2/m3 이상으로 부여되어야 함을 확인하였다.

결정성장 도중 전류에 의해 고/액 계면에서 발생하는 Peltier 열을 이용하면 온도구배의 증가와 이에 따른 성장속도의 증가 및 결정성의 향상에 기여할 것이라 예상되어, 고/액 계면에서 복합적으로 발생하는 Peltier 효과를 조사하였다. 전류 밀도, 극성 및 온도구배의 변화에 따른 고상과 액상 및 그 계면에서의 온도변화로부터 이론적 추론에 의해 Peltier 열, Thomson 열 및 Joule 열만의 영향으로 분류할 수 있었고, 고상/액상 계에 대한 Peltier 계수 및 Thomson 계수도 구할 수 있었다.

In this study, multipoint dynamic vertical displacement of liquid in the tuned liquid damper (TLD) is measured by a laser Doppler vibrometer (LDV) and a Galvanometer scanner to overcome limitations of existing sensors and to leverage noncontact sensing.