[en] As part of the UK development work an experimental programme is in progress to measure the acoustic transmission through an actual reactor SGU and also through a model tube bundle in the laboratory. This paper gives an outline of the experimental arrangements and examples of the preliminary results. The data from the laboratory measurements in particular is being used for comparison with theoretical studies carried out at the University of Keele which are reported in a separate paper to this Specialist's Meeting. The plant measurements are being carried out on a Superheater unit of the Prototype Fast Reactor (PFR) at Dounreay. These measurements are primarily aimed at providing information for a loose parts condition monitoring system which is operated on the PFR SGU, but results obtained will make a significant contribution to the acoustic leak detection programme. The Superheater used for the experiment has six blank steam tubes for experimental purposes. An impacting device has been inserted into one of the blank tubes and acoustic signals recorded on waveguides which are attached to the SGU shell. Recordings were made during a reactor shutdown with static sodium in the superheater and with the impacting device at five axial positions in both the inner and outer legs of the 'U' tube. Results are given for signal attenuation and location of the acoustic noise source. The laboratory measurements are being made using a 721-tube model tube bundle in a water tank. The tube bundle which is approximately 0.75m diameter x 3 metres long is not modelled to a specific design but is of realistic size and construction. A piezo-electric acoustic source is mounted centrally in the tube bundle and the transmitted signal is received by underwater microphones on the periphery of the bundle. Results from the first experiments with water filled tubes are given covering a frequency range of 6KHz to 80KHz. The preliminary results of the experimental programme are encouraging and indicate that while the transmission is complex the attenuation will not be too severe for an effective acoustic leak detection system. 2 refs, 17 figs

[en] A number of important molecular checkpoints are believed to control the orderly progression of cell cycle events. We have found that the radiation-sensitive Schizosaccharomyces pombe mutant rad3-136 is deficient in two molecular checkpoint functions. Unlike wild-type cells, the mutant cells are unable to arrest in the G2 phase of the cell cycle after DNA damage by gamma-irradiation and are also incapable of maintaining the dependence of mitosis upon the completion of DNA synthesis. An S. pombe genomic clone that complements the UV sensitivity of the rad3-136 mutant completely restores the missing checkpoint functions. The rad3 gene is also likely to play a role in DNA repair

[en] This paper gives an outline description of an acoustic monitoring system which has been installed on the SGU of the Prototype Fast Reactor (PFR) at Dounreay with the objective of giving early warning of any change in noise output which could be related to potentially damaging vibrations within the units. Data obtained from this PFR monitoring system is playing an important part in the development of acoustic instrumentation for leak detection although this had not been the primary objective of this particular installation. The PFR has three secondary circuits each containing an evaporator, a superheater and a reheater giving a total of nine SGUs. Although the design of the units is different from that intended for EFR, the measurements provide a valuable source of information on the character and amplitude of acoustic background noise in operational steam generator units. The vibration monitoring system uses the waveguides originally installed during reactor commissioning for leak detection studies. Twelve acoustic waveguides are fitted to the shell of each of the units. The superheaters and reheaters have three waveguides at each of four axial levels, while the evaporators have four waveguides at each of three axial levels. In addition the evaporators have a small number of waveguides attached to the top flange of the unit. Each waveguide is fitted with an accelerometer to record the acoustic signal from the SGU. Tape recordings of the acoustic noise from each unit are made on a regular basis and the tapes analysed on an automated analysis system which has been developed to extract and store in a database about 20 characteristic features from the data. The paper gives examples of the background noise from the SGU. The data demonstrates the use of location techniques to identify prominent acoustic source. 8 figs

[en] Irradiated cells are arrested in G/sub 2/ (transition point [TP] = 32 min before cell selection in mitosis). Irradiated cells do not recover from G/sub 2/ arrest in the presence of cycloheximide (CHM) indicating dependence of recovery on protein synthesis. Irradiated cells in the presence of caffeine progress to mitosis without arrest. The authors investigate whether irradiated cells in the presence of caffeine require protein synthesis to progress to mitosis. Mitotic cell selection was used to monitor the progression of irradiated CHO cells (150 rad) during exposure to 5 mM caffeine and/or 50 μg/ml CHM. Protein synthesis inhibition was confirmed using /sup 3/H-leucine incorporation. Cells exposed to CHM alone are arrested in G/sub 2/ (TP=49 min), thus cells beyond this point have synthesized all proteins necessary for entry into mitosis. In the presence of caffeine, unirradiated cells exposed to CHM are not arrested at all in G/sub 2/, instead arrest occurs near the S/G/sub 2/ boundary (TP=95 min) indicating that caffeine alleviates the dependence of G/sub 2/ cell progression on protein synthesis. However, irradiated cells exposed to both caffeine and CHM are only able to progress to mitosis if beyond the CHM-TP. Irradiated cells in the presence of caffeine thus behave as untreated cells and require protein synthesis for progression to mitosis when prior to the CHM-TP

[en] Exponentially growing eucaryotic cells, irradiated in interphase, are delayed in progression to mitosis chiefly by arrest in G₂. The sensitivity of Chinese hamster ovary cells to G₂ arrest induction by X rays increases through the cell cycle, up to the X-ray transition point (TP) in G₂. This age response can be explained by cell cycle age-dependent changes in susceptibility of the target(s) for G₂ arrest and/or by changes in capability for postirradiation recovery from G₂ arrest damage. Discrimination between sensitivity changes and repair phenomena is possible only if the level of G₂ arrest-causing damage sustained by a cell at the time of irradiation and the level ultimately expressed as arrest can be determined. The ability of caffeine to ameliorate radiation-induced G₂ arrest, while inhibiting repair of G₂ arrest-causing damage makes such an analysis possible. In the presence of caffeine, progression of irradiated cells was relatively unperturbed, but on caffeine removal, G₂ arrest was expressed. The duration of G₂ arrest was independent of the length of the prior caffeine exposure. This finding indicates that the target for G₂ arrest induction is present throughout the cell cycle and that the level of G₂ arrest damage incurred is initially constant for all cell cycle phases. The data are consistent with the existence of a time-dependent recovery mechanism to explain the age dependence for radiation induction of G₂ arrest

[en] This paper describes acoustic measurements made during a number of sodium/water reaction experiments in the UK. The tests have included water and steam injections through both realistic (fatigue crack) defects and machined orifices and have covered a range of experimental conditions including those appropriate to the inlet and outlet regions of the EFR steam generators. Injection rates were typically in the range 0.1 to 30 g/s. Where possible, gas injections were also included in the test programme for comparison, since it is anticipated that a practical SGU acoustic leak detection system would include a facility for gas injections to allow system calibration, and to confirm transmission properties within the SGU. The test sections were instrumented with accelerometers on waveguides and in some cases included an under-sodium microphone situated about 300mm above the reaction zone. Tape recordings were made during the tests and used for detailed analysis off-line, although an audible output from one of the acoustic channels was used to monitor the progress of the injections and provide information for the rig operators. A comparison of the signal amplitudes measured during the experiments with typical reactor background noise was made and an estimate of the detection sensitivity of an acoustic monitoring system was deduced. 3 refs, 5 figs, 1 tab

[en] The paper presents a brief review of the acoustic techniques applicable to the detection of steam generator unit leaks that have been studied in the UK. Before discussion of the acoustic detection methods a reference representation of the required performance as developed in the UK is given. The conclusion is made that preliminary specification for the acoustic leak detection of sodium/water leaks in steam generating units suggests that it will be necessary to detect better than a leak rate of 3 g/s within a few seconds. 10 refs, 12 figs

[en] Acoustic excitation is a principal source of vibration in PFR. Pumps produce acoustic pressures of up to 2.2 psi at twice blade passing frequency which is 224Hz at full speed. This excites structural resonances particularly an upper duct ovalling mode at 170Hz and other modes in the lower ducts and primary tanks. Stresses are small, the broadband level being below 300 psi rms and single frequency components below 100 psi. Loss factors have been measured and range from 0.005 to 0.1 on different components. Asymmetric pump operation produces a random pressure fluctuation attributed to non-return valve flutter when the speeds differ by more than a critical few per cent. (author)

[en] In the presence of 5 mM caffeine, irradiated (1.5 Gy) S and G₂ cells progressed to mitosis in register and without arrest in G₂. Caffeine (5 mM) markedly reduced mitotic delay even after radiation doses up to 20 Gy. When caffeine was removed from irradiated (1.5 Gy) and caffeine-treated cells, a period of G₂ arrest followed, similar in length to that produced by radiation alone. The arrest expressed was independent of the duration of the caffeine treatment for exposures up to 3 hr. The similarity of the response to the cited effects of caffeine on S-phase delay suggests a common basis for delay induction in S and G₂ phases

[en] Data from boiling noise experiments in the BOR60 reactor in USSR has been supplied by the IAEA to enable analysis techniques to be compared. The signals have been analysed at RNL using two basic techniques. High Frequency RMS analysis Pulse Counting analysis together with two more sophisticated methods, Pattern Recognition and Pulse Timing analysis. All methods indicated boiling successfully, pulse counting proved more sensitive than RMS for the detection of the onset of boiling. Pattern Recognition shows promise of a very reliable detector provided the background can be defined. Data from an ionisation chamber was also supplied and there was good correlation between neutronic and acoustic signals. (author). 3 refs, 25 figs, 3 tabs