[en] Flaw depth evaluation was performed on the priamry water stress corrosion cracking in steam generator tubing, with the eddy current test results such as signal amplitude and phase angle. The relationship between crack length and crack depth was also investigated, based on the metallogrphic results of pulled-out tubings. This study yields the following results and conclusions: (1) there is no correlation between crack length and crack depth. (2) it is not easy to correlate the crack depth with phase angle. (3) although signal amplitude appears to be related with crack length, the latter cannot exactly be obtained from the former value. (4) since most cracks with the length above 6 mm could be a through-crack, it would be helpful to plug that tubing in order to prevent tube-leaking

[en] Crack shape of PWSCC was analyzed, based on the fractured pulled-out S/G tubings of Ulchin-1 steam generator. The shape of the cracks in kiss roll transitions was elliptical shape for short cracks, and car shape for long cracks with flat crack front. The bulging was observed under the inner wall after shot-peening. Crack shape change after shot-peening was resulted from the crack growth restraint in axial direction due to compressive residual stresses on the primary side surface

[en] A methodology has been suggestd to develop a module, which is able to estimate the steam explosion load under the integral code structure. As the first step of module development, TEXAS-V, which is a one-dimensional mechanistic code for steam explosion analysis, was selected and sample calculations were done. At this stage, the characteristics of the TEXAS-V code was identified and the analysis capability was setup. A sensitivity study was also performed on the uncertain code parameters such as mesh number, mesh cross-sectional area, mixing completion condition, and triggering magnitude. The melt jet with the diameter of 0.15m and the velocity of 9m/s was poured into the water at 1 atm, 363K, and 1.1 m depth during 0.74 sec. 197kg of melt was mixed with the water among the total of 947kg. The explosion peak pressure, propagation speed, and conversion ratio considering the mixed melt, were evaluated as 40MPa, 1500m/s, and 2%, respectively. The triggering magnitude did not show any effect on the explosion strength once the explosion would be started. The explosion violence was sensitive to the mesh number, mesh area, and mixing completion condition, mainly because the mixture condition is dependent upon these parameters. The additional study on these parameters needs to be done

[en] A steam explosion module, STX, has been developed using the mechanistic steam explosion analysis code, TEXAS-V, in order to estimate the dynamic load with steam explosion by implementing the module to the integrated safety analysis code, MELCOR. One of the difficulties in using mechanistic steam explosion codes is that they do not have any obvious criteria for defining some uncertain parameters such as triggering timing, triggering magnitude, mesh axial length and mesh cross-sectional area. These parameters have been user decision parts in the past. Steam explosion sample calculations and sensitivity studies on uncertain parameters were conducted to investigate those uncertain parameters. The TEXAS-V simulations were summarized in the format of a look-up table and a linear interpolation technique was adopted to calculate the steam explosion load between the data points in the table. The STX-module merged with MELCOR showed the same results as the original MELCOR and additionally it could estimate the steam explosion load in the reactor cavity

[en] MELCOR code has been improved to estimate ex_vessel explosion work. First, steam explosion sample calculations and sensitive studies on uncertain parameters at PWR cavity were conducted using TEXAS-V, which is a mechanistic steam explosion analysis code. TEXAS-V simulations were performed to evaluate steam explosion work based on the thermal-hydraulic conditions of fuel and coolant, which cover the actual situation during the accident. Those results were used to prepare the look-up table. That table and Largangian interpolation scheme were merged into MELCOR code. To simulate fuel-coolant interaction at the reactor cavity. MELCOR input data were prepared. It was found that the improved MELCOR could estimate the steam explosion work at the reactor cavity from the look-up table for a given initial condition calculated from MELCOR. As the steam explosion module is limited by the upper and lower boundary of the look-up table parameters, these boundaries will be expanded to cover various accident sequences

[en] The triggerability and explosivity in the molten fuel and coolant interactions(FCIs) were discussed. For the triggerability, small scale experiments using single molten droplets and analytical triggering models were reviewed and large scale experiments and a simple model were discussed for the explosivity. These works revealed that the thermal-hydraulic condition depending upon the physical properties of the molten material is an important role in vapor explosions. However, there exist some uncertainties due to the simulant material or the limited experimental dimension in reasonable explanations for vapor explosions during the reactor severe accidents. Therefore, the real melt simulations under various geometries are necessary for properly answering the reactor safety issues related to vapor explosions during reactor severe accidents

[en] Many of the fuel coolant interaction (FCI) processes are not fully understood which is especially true for the exotic parameter range encountered in nuclear safety problems. Therefore there are a variety of models for the important phenomena of FCIs. The purpose of the present work is to use the experiments that have been performed at Forschungszentrum Karlsruhe during the last ten years for determining the most appropriate models and parameters for premixing calculations. This is done by recalculating experiments in two steps: 1. The results of a QUEOS 58 are used to fix the parameters concerning a heat transfer. The QUEOS the experiments are especially suited for this purpose as they have been performed with small hot solid spheres. Therefore the area of a heat exchange is known. 2. With the heat transfer parameters fixed in this way, a PREMIX experiment is recalculated. In this paper, the first step for a heat transfer correlation is presented. All the calculations of this work have been performed with MC3D version 3.5 patch1,by CEA, France, which is owned by IRSN, France

[en] Radiation therapy in combination with surgery has an important role in the therapy of the head and neck cancer. We conducted a prospective study for patients with head and neck cancer treated with surgery and radiation to evaluate the effect of therapies on the thyroid gland, and to identify the factors that might influence the development of hypothyroidism. From September 1986 through December 1994, 71 patients with head and cancer treated with surgery and radiation were included in this prospective study. Patients' age ranged from 32 to 73 years with a median age of 58 years. There were 12 women and 59 men. Total laryngectomy with neck dissection was carried out in 45 patients and neck dissection alone in 26 patients. All patients were serially monitored for thyroid function before and after radiation therapy. Radiation dose to the thyroid gland ranged from 40.6Gy to 60Gy with a median dose of 50Gy. The follow-up duration was 3 to 80 months. The overall incidence of hypothyroidism was 56.3% (40/71); 7 out of 71 patients (9.9%) developed clinical hypothyroidism and 33 patients (46.4%) developed subclinical hypothyroidism. No thyroid nodules, thyroid cancers, or hyperthyroidism was detected. The risk factor that significantly influenced the incidence of hypothyroidism was a combination of surgery (total laryngectomy with neck dissection) and radiation therapy (P=0.0000). Four of 26 patients (15.4%) with neck dissection alone developed hypothyroidism while 36 of 45 patients (80%) with laryngectomy and neck dissection developed hypothyroidism. The hypothyroidism following surgery and radiation therapy was a relatively common complication. The factor that significantly influenced the incidence of hypothyroidism was combination of surgery and radiation therapy. Evaluation of thyroid function before and after radiation therapy with periodic thyroid function tests is recommended for an early detection of hypothyroidism and thyroid hormone replacement therapy is recommended whenever hypothyroidism develops. (author)

[en] Korea Atomic Energy Research Institute (KAERI) has been carrying the fuel-coolant interaction (FCI) experiments called the Test for Real cOrium Interaction with water (TROI) program using the reactor material. As a part of the program, the melting and release method of oxide materials with high melting points has been studied. The melting experiment of UO2/ZrO2 mixture (w/o 8:2) is carried out using the cold crucible melting method. About 10 kg melt is obtained from the melting experiments and was successfully applied to FCI experiments. The heat transferred to the induction coil, the cold crucible and melt is calculated using operating parameters of R. F generator. Also, the superheat of melt is predicted from heat balance analysis between the heat input, which is transferred to the cold crucible and melt, and the heat loss, which is removed through the cooling water from the crucible and the radiation from the melt surface. The melt is superheated over 500K in maximum from the calculation result. Meanwhile, when the two-color pyrometer is used for the temperature measurement, the emissivity ratio has to be set but depends on the surrounding conditions. In the UO2/ZrO2 test, the emissivity ratio of the pyrometer is guessed about 1.18

[en] The corrosion resistance of Zr-Nb-Sn-Fe-X alloys were evaluated by the autoclave tests under the environments of 360 .deg. C water, 360 .deg. C LiOH 70 ppm solution and 400 .deg. C steam. The mechanical properties of those alloys were also investigated by tensile tests and creep tests. The corrosion resistance of the alloys in the water and the LiOH solution showed similar behavior, while they are superior to that of Zircaloy-4 in LiOH solution. The alloys, which have much in alloying content, showed better properties in tensile strength and creep resistance due to alloying effect. The final heat treatment of the alloys at 470 .deg. C and 520 .deg. C has little differences in corrosion behavior but much in mechanical strength and creep strength because the heat treatment at 470 .deg. C has more dislocation barrier than that at 520 .deg. C