[en] The feed water system of Fugen plant is almost same as that of BWR plants, and the metallic impurities in feed water are brought into the core and activated. These radioactive products circulate through the primary system together with coolant, and accumulate on the surfaces of fuel and pipings, thus they raise ambient radiation dose rate, and cause problems in the exposure control of workers and the management of wastes. Most of the metallic impurities is iron, and its source of generation is the carbon steel pipings around the condenser and in the feed water system. The form of existence of the iron is roughly divided into ions and cruds, and as the countermeasure to reduce it, the oxygen injection into feed water was attempted at the time of the start-up test of Fugen plant. In order to prevent corrosion by raising potential up to passive state region, the environmental condition is to be changed to oxidizing atmosphere, and for the purpose, the method of increasing dissolved oxygen is adopted. Feed water and steel pipes are separated by the protecting coating of iron oxide, and the corrosion is suppressed. The testing method and the results are explained. When 30 ppb and 50 ppb of oxygen were injected at the outlet of the condensate desalting apparatus, the concentration of ionic iron was lowered to about 1 ppb, and this value is equivalent to about 1/10 of the previous value. (J.P.N.)

[en] A supersonic heavy water monitor was developed in the Fugen Nuclear Power Station. The accuracy is confirmed with a conventional near-infrared light absorption method. The monitor shortened sampling/measurement time and saved man power to observe the heavy water isotopic purity change during deuteration/dedeuteration with resin exchange of heavy water purification system. The monitor also reduced the amount of degraded heavy water unproperly storaged since operators in deuteration/dedeuteration procedures can change low/high concentration heavy water storage tanks quickly and properly following the indication of the monitor. (author)

[en] The aim of this study was to assess the diagnostic performance of ¹⁸F-Fluoride positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) compared with bone scintigraphy (BS) planar or BS planar and single photon emission computed tomography (SPECT) in evaluating patients with metastatic bone tumor. We performed a meta-analysis of all available studies addressing the diagnostic accuracy of ¹⁸F-Fluoride PET, ¹⁸F-Fluoride PET/CT, BS planar, and BS planar and SPECT for detecting the metastatic bone tumor. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios, and drew summary receiver operating characteristic curves using hierarchical regression models. We also compared the effective dose and cost-effectiveness estimated by data from the enrolled studies between ¹⁸F-Fluoride PET or PET/CT and BS planar or BS planar and SPECT. When comparing all studies with data on ¹⁸F-Fluoride PET or PET/CT, sensitivity and specificity were 96.2% [95% confidence interval (CI) 93.5-98.9%] and 98.5% (95% CI 97.0-100%), respectively, on a patient basis and 96.9% (95% CI 95.9-98.0%) and 98.0% (95% CI 97.1-98.9%), respectively, on a lesion basis. The Az values of ¹⁸F-Fluoride PET or PET/CT were 0.986 for the patient basis and 0.905 for the lesion basis, whereas those of BS or BS and SPECT were 0.866 for the patient basis and 0.854 for the lesion basis. However, the estimated effective dose and average cost-effective ratio were poorer for ¹⁸F-Fluoride PET or PET/CT than those of BS planar or BS planar and SPECT. ¹⁸F-Fluoride PET or PET/CT has excellent diagnostic performance for the detection of metastatic bone tumor, but the estimated effective dose and average cost-effective ratio are at a disadvantage compared with BS planar or BS planar and SPECT. (author)

[en] We prove several theorems to give sufficient conditions for convergence of quantum annealing, which is a protocol to solve generic optimization problems by quantum dynamics. In particular, the property of strong ergodicity is proved for the path-integral Monte Carlo implementation of quantum annealing for the transverse Ising model under a power decay of the transverse field. This result is to be compared with the much slower inverse-log decay of temperature in the conventional simulated annealing. Similar results are proved for the Green's function Monte Carlo approach. Optimization problems in continuous space of particle configurations are also discussed

[en] A new type cartridge filter which can remove γ ray activity like ⁶⁰Co in degrated heavy water has been developed. This cartridge filter consists of oxine-impegnated active charcoal and has excellent characters like followings, · γ ray activities like ⁶⁰Co are easy to remove. (DF is more than 1000.) · Handling is easy. · All of Used cartridge can be incinerated. This report presents a summary of basic characteristic test of removement ability of ⁶⁰Co in degraded heavy water using oxine-impegnated active charcoal, and demonstration test using actual cartridge filter. (author)

[en] Applicability of the zinc injection technique for reducing the equivalent dose of annual inspection workers has been cleared and confirmed by several out-of-pile tests at Fugen Nuclear Power Station. A trial, which aimed at compressing the dose rate increase, was developed by BWR and was carried out in several plants from 1986. And then, regular zinc injections were started from Aug. 1999 after the start up of the 15^th annual inspection. As a result of this injection, the ⁶⁰Co ion concentration in reactor has been reduced by the order of about 30%, and a radioactivity reduction effect has also been confirmed. Also, the rebuild up rate of ⁶⁰Co on piping surfaces has been drastically reduced from about 60% to about 12% after system decontamination. According to an analysis of the practical method, the adhesive rate coefficient of ⁶⁰Co to metal oxide film is compressed to about 1/3. (author)

[en] A system decontamination of the B-loop of the reactor cooling system of FUGEN was carried out by the newly developed oxidization-reduction decontamination method (the HOP process using hydrazine, oxalic acid and potassium permanganate) in February 1999. The purpose of the decontamination was to reduce the exposure dose during the overhaul work of the re-circulation pumps, and to achieve effective suppression of the surface radioactivity build-up by combining the decontamination with the zinc injection which follows the decontamination. As a result of the decontamination, the dose rate of the piping surface in the overhaul work area decreased sufficiently, and a high average decontamination factor of up to 20 was obtained. The dose equivalent during the overhaul work was reduced to 0.8 man·Sv, which was about 1/6 of the 4.5 man·Sv estimated in the case of no decontamination. (author)

[en] With regards to the chemistry control of reactor coolant, a water chemistry control technique, which mainly aims to confirm and maintain the integrity of reactor construction material including fuel clad and aims to lower the exposure dose, has been adopted at Fugen NPS just like other LWRs. Fugen applied hydrogen injection from 1985 for the first time in Japan, until its operational termination, as a countermeasure against stress corrosion cracking with equipment and piping of reactor coolant system. Additionally, Fugen implemented full system chemical decontamination for the reactor coolant system in 1989 as a measure to reduce the dose of radiation to which workers are exposed. However, re-contamination was recognized and zinc injection was introduced as a technology to suppress the re-contamination. Zinc injection was carried out to the reactor coolant system from 1999, just after the third chemical decontamination of Fugen NPS. The establishment of these water chemistry control techniques ensured the suppression of stress corrosion cracking of the reactor coolant system. At the same time, it reduced the dose of radiation to which workers who are engaged in the periodical inspection outage at Fugen NPS are exposed. (author)

[en] Reactivity control of the Fugen Nuclear Power Station is performed by the control rods and the adjustment of the concentration of ¹⁰B dissolved in the heavy water as boric acid. An accurate evaluation of the ¹⁰B concentration in the heavy water is important in order to determine the excess reactivity. It has been a conventional method to sample the heavy water and measure the ¹⁰B concentration in it directly, which is time- and labor-consuming and, moreover, costly. We have developed an economical and expedient calculation method to determine the ¹⁰B concentrations in the heavy water. This method uses a model of boric acid injection, boric acid removal, poison burning in the core and heavy water purification system. The calculation result has been evaluated by the comparison of calculated ¹⁰B concentrations with the data obtained by mass spectrometry method, and the calculation accuracy is approximately ± 0.1 ppm. This calculation program is practical and successfully in use now. (author)

[en] Heavy water and helium system of the Fugen, a 165 MWe prototype of heavy water moderated, boiling light water cooled, pressure tube type reactor, has demonstrated its excellent performance and reliability through over ten years' operation. Heavy water chemistry control method was also established after a number of R and D works against degradation of purification resins with deuteriumperoxide generated from heavy water rediolysis. An overview of the ten years' operational experience is described concerning maintenance works, operational procedures, heavy water chemistry control, and radiation protection methods against tritium internal exposure. (author)