Mitsuo Naritomi

Performance of Containment Sprays for Light Water Reactors and Evaluation of the Heat Transfer

Capacity curves, spray distributions, and droplet size distributions of light water reactor (pressurized water reactor (PWR) and boiling water reactor (BWR)) containment spray nozzles are obtained, and the heat removal effectiveness is evaluated by a computer program CONDENSE. It is revealed by the calculations that spray droplets from a PWR spray nozzle always attain the containment atmosphere temperature and spray droplets from a BWR spray nozzle attain the containment atmosphere temperature above approximately 70/degree/C. 16 refs.

Behavior of Sodium Aerosol in Atmosphere

Experiments have been made to determine the behavior of sodium aerosol under various atmospheric conditions, with the view to establishing an air monitoring technique to be used in sodium-cooled fast reactors. Changes in both size and form of sodium aerosol particles released into the air were studied. At levels of humidity below 40%, the particles were observed to be in solid state, constituted of sodium oxides and sodium hydroxide. When sodium aerosol particles are exposed for more than 1 min in an atmosphere containing more than 60% humidity, they are mostly converted into droplets of sodium hydroxide. The size of the droplets increases with humidity, the diameter becoming at 95% humidity about 1.4 times that at 40% (2. 7 times in volume). The final state of sodium aerosol suspended in air with a humidity exceeding 90% is in the form of droplets of sodium carbonate. When the CO2 concentration in the air is as high as 1.0v/o, the droplets solidify even at a humidity of 70%. The droplets can be made to s...

Iodine removal tests for BWR containment spray by large scale facility.

Iodine removal tests for a BWR containment spray were carried out with large-scale JAERI Model Containment Test Facility under LOCA simulated conditions. The tests consisted of two groups: “gas-phase based” tests mainly to obtain the initial iodine removal rate by the spray and “liquid-phase based” tests to obtain the iodine partition coefficient at equilibrium state. It was shown that the degree of iodine removal was largely influenced by pH-value of spray water. The results were discussed with calculated results by a code MIRA-PB using a dose reduction factor for the airborne iodine.

Method for Improving the Collecting Performance of Iodine Samplers under High Relative Humidity

In airborne radioiodine monitoring, it is essential to establish an effective sampling technique that gives results independent of the form taken by the radioiodine and that works effectively under high humidity. Experiments were made to improve the performance of an iodine sampler embodying (a) cellulose asbestos filter paper (Toyo Roshi, Type HE-40) and activated charcoal filter paper (Toyo Roshi, Type CP-20) and (b) HE-40 filter paper and activated charcoal cartridge (Toyo Roshi, Type CHC-50). Based on the results, a new sampler was devised in which the air is heated to 70°∼90°C before reaching the filters. The dependence of the collecting efficiency on the chemical form taken by the airborne iodine and also on the duration of sampling period was studied.Severe conditions of environment, such as high humidity, were simulated in the experimental apparatus. The airborne radioiodine used was a mixture of inorganic and organic iodides, identified by radio-gaschromatography. It was found that the collecting efficiency of the sampler with activated charcoal cartridge and the activated charcoal filter paper, respectively, exceeded 99.5% and 85%, regardless of the form of airborne iodine even at 100% relative humidity throughout the whole range of sampling duration up to 16hr. Under conditions of high humidity, the collecting efficiencies were found superior to that of charcoal filter paper and charcoal cartridge impregnated with TEDA or SnI2 used without air heating.

Chemical Forms of Airborne Radioiodine in the Exhaust Air from Iodine-131 Production Plant

Airborne radioiodine released from the reaction cell into the exhaust air during the processing operations at an 131I production plant has been analyzed by radio-gaschromatography. The iodine compounds observed were CH3 131I, C2H5 131I, H131IO4 and H131IO3. The distribution of the total 131I among these compounds differs greatly according to the time of sampling after the start of processing. In the beginning, H131IO3 is highly predominant, but the content of organic iodides increases with progress of the processing operation. The removal efficiency of the charcoal filter installed in the stream of the exhaust air was better than 85% for the total 1311 but less than 50% when organic iodides alone were taken into account, indicating poorer efficiency of the filters for the latter compounds. The total amount of CH3 131I released was of Mc1 order. This suggests a very promising new method for obtaining CH3 131I as a by-product without any special chemical treatment.

Heat Removal Tests for Pressurized Water Reactor Containment Spray by Large-Scale Facility

Heat removal tests for pressurized water reactor (PWR) containment spray were carried out to investigate effectiveness of the depressurization by Japan Atomic Energy Research Institute model containment (7-m diameter, 20 m high, and 708-m/sup 3/ volume) with PWR spray nozzles. The depressurization rate is influenced by the spray heat transfer efficiency and the containment wall surface heat transfer coefficient. The overall spray heat transfer efficiency was investigated with respect to spray flow rate, weight ratio of steam/air, and spray height. The spray droplet heat transfer efficiency was investigated whether the overlapping of spray patterns gives effect or not. The effect was not detectable in the range of large value of steam/air, however, it was better in the range of small value of it. The experimental results were compared with the calculated results by computer code CONTEMPT-LT/022. The overall spray heat transfer efficiency was almost 100% in the containment pressure, ranging from 2.5 to 0.9 kg/cm/sup 2/ X G, so that the code was useful on the prediction of the thermal hydraulic behavior of containment atmosphere in a PWR accident condition.

Containment Spray Model for Predicting Radioiodine Removal in Light Water Reactors

The computer code COSMO (containment spray model) is prepared to provide information on radioiodine removal by the containment spray of boiling water reactors and pressurized water reactors involving an ice-condenser-type reactor in the event of a loss-of-coolant accident (LOCA). The code considers the removal of inorganic iodine, organic iodide, and particulate iodine in multiple compartments, taking into consideration natural deposition onto the containment wall, spray washout, liquid-film absorption, filtration, and leakage to the environment. The code is also developed by adding many abilities such as the gas convection flow between multicompartment rooms due to fluid disturbance and spray covering onto the inner structures involving the wall in the containment vessels. The calculated results are compared with the iodine removal tests of the Japan Atomic Energy Research Institute model containment, and the iodine removal for light water reactors of 1000 MW(electric) in the postulated LOCA conditions i...

AIRBORNE IODINE MONITORING AT THE RADIOISOTOPE TEST PRODUCTION PLANT, JAERI

Abstract During production of iodine-131 from an irradiated telluric acid (H2TeO4) by the distillation method, a considerable amount of airborne radioiodine is generated in the cell and its major portion is discharged to the atmosphere through a stack after passing through air cleaning systems, consisting of prefilters, charcoal filters and high efficiency particulate filter. Some minor portion of airborne iodine generated leaks directly out of the cell to the service area and operation area, although a negative pressure is maintained in the cell. To evaluate the airborne iodine concentration in air and the amount discharged as accurately as possible, extensive radiation monitoring was performed using various kinds of monitoring devices. As one of these devices, an iodine sampler was developed which is composed of three sampling components, i.e. HV-70 filter paper, charcoal-impregnated filter paper and charcoal cartridges. At several sampling positions of the air cleaning systems, the overall collection efficiency of the sampler was evaluated by taking into account activities collected in cold traps (containing granular charcoal) which are connected to the sampler in series. It was found that the overall collection efficiency ranges from 70% to 100%, highly dependent on whether the samples were taken at upper stream or downstream of the air cleaning systems. Data obtained from the airborne iodine monitoring at the stack and in the working areas conducted during the iodine-131 test production are presented, and internal exposures of the operating personnel received by inhaling the airborne iodine are described in relation to the air contamination of the working areas.

Calibration of Cascade Impactor by Two-Stage Method

A simple method of calibrating the cascade impactor has been developed by applying Hongo et al.s two-stage method to evaluate the particle-size distribution. The constants ψ and σfor a function representing the impaction efficiency were determined for the UNICO cascade impactor, using the test particles produced by a spinning-disc aerosol generator. The values were ψ=0.35, σ=1.46, respectively. The validity of the method for the UNICO cascade impactor was confirmed from microphotographic observation of a sample artificial aerosol containing different sizes of uranine methylene-blue particles. Both the mass median aerodynamic diameter and the geometric standard deviation obtained with the method agreed with the microphotographie measurements with relative errors not exceeding 10%.