The thermal neutron capture cross section (σ 0) and the resonance integral (I 0) of 166m Ho have been measured as data for the transmutation of nuclear waste. Samples of 166m Ho were made by the neutron irradiation of 165 Ho. Two metallic foils of 165 Ho were irradiated for 2 weeks and two others for 3 weeks at the Kyoto University Reactor. A high purity Ge detector was employed for activity measurement. The samples irradiated were cooled for 3 months to reduce the activity of 166g Ho. One of the samples irradiated for 2 weeks was irradiated again with Cd cover sheets and the other one without a Cd cover sheet. For the samples irradiated for 3 weeks, the same irradiation was performed. The 167 Ho nuclei were produced at the second irradiation via the neutron capture of 166m Ho and the double neutron capture of 165 Ho. The amount of 167 Ho via the double capture was estimated from the difference between the data of 2 week irradiation and 3 week irradiation, and corrected. The reaction rate to produce 167 Ho from 166m Ho was analyzed by Westcott's convention. A resonance at 0.274 eV was considered in the analysis. The results obtained were 3.11±0.82 kb for the σ 0 and 10.0±2.7 kb for the I 0 of 166m Ho.

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The thermal neutron capture cross section (σ 0 ) and the resonance integral (I 0 ) of 166m Ho have been measured as data for the transmutation of nuclear waste. Samples of 166m Ho were made by the neutron irradiation of 165 Ho. Two metallic foils of 165 Ho were irradiated for 2 weeks and two others for 3 weeks at the Kyoto University Reactor. A high purity Ge detector was employed for activity measurement. The samples irradiated were cooled for 3 months to reduce the activity of 166g Ho. One of the samples irradiated for 2 weeks was irradiated again with Cd cover sheets and the other one without a Cd cover sheet. For the samples irradiated for 3 weeks, the same irradiation was performed. The 167 Ho nuclei were produced at the second irradiation via the neutron capture of 166m Ho and the double neutron capture of 165 Ho. The amount of 167 Ho via the double capture was estimated from the difference between the data of 2 week irradiation and 3 week irradiation, and corrected. The reaction rate to produce 167 Ho from 166m Ho was analyzed by Westcott's convention. A resonance at 0.274 eV was considered in the analysis. The results obtained were 3.11±0.82 kb for the σ 0 and 10.0±2.7 kb for the I 0 of 166m Ho.

Titrimetry is a classical analytical method that is still widely in use. It is adopted, for example, as a method for the quantitative analysis of nearly 60% of drugs listed in Part 1 of the Japanese Parmacopoeia. 1 According to a book by Szabadváry, 2 the origin of titrimetry can be traced back to 1729 when Geoffroy analyzed vinegar samples with K2CO3. However, conventional manual titration using glassware, such as a burette, is tedious and time-consuming. Various flow titration techniques have therefore been developed, as recently reviewed by Tanaka and Nakano. 3These include flow injection titration, 4 sequential injection titration, 5 triangle programmed coulometric titration, 6-8 flow ratiometric titration 9,10 and monosegmented flow titration. 11 Tanaka et al. 12,13 proposed a feedback-based flow ratiometry, a new concept for continuous titration. In their approach, the titrant flow rate is linearly varied while the total (titrant + titrand) flow rate (FT) is held constant. The scan direction of the titrant flow rate is reversed from upward to downward, and vice versa, whenever the equivalence point EP is detected. Thus, the scan range is limited to the range around EP. A high throughput was attained for photometric 12 and potentiometric 13 titrtions (6 and 5 titrations per minute, respectively). Jo and Dasgupta 14 applied this method to cheletometric titrations.Very recently, we introduced a new strategy to feedback-based flow ratiometry. 15 After feedback-based operation, fixed triangular waves were used to control the titrant flow rate in order to further limit the scan to the range of interest. The developed method realized potentiometric titrations having an extremely high throughput rate at reasonable precision (maximally 17.6 titrations per minute at RSD = 0.35%). In the present study, we extended the principle of the method to photometric titrimetry, because the photo-sensor is one of the most popular detectors in flow analyses, and is expected to have a quicker response than an electrode. ExperimentalFlow system Figure 1 shows the flow system of the present study. The principle of flow ratiometry for high-throughput titration, which we recently proposed for potentiometric titration, was extended to photometric titration. The flow rate (FB) of a base solution containing an acid-base indicator was linearly varied in response to a control voltage (Vc) generated from a computer. With the total (acid + base) flow rate (FT) being kept constant, the base solution was merged with an acid solution, which was aspirated to the confluence point at a flow rate of FT -FB. Downstream, the relative transmittance of the mixed solution was measured at the maximum absorption wavelength of the base form of the indicator. Initially, a feedback-based control was applied, where the scan direction of Vc was reversed from upward to downward, and vice versa, whenever the transition of the indicator at the equivalence point (EP) was sensed. Next, the scan range of Vc was further limited to the range just around EP by using f...

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