[en] This is an impression of Darlington Nuclear Generating Station, written mainly for a general readership. 1 fig., 2 ills

[en] The Ultrasonic Cross-Correlation Flow Meter (USCCFM) has been used for regular feedwater flow calibration at Darlington NGS since the early nineties. Typical measurement repeatability over the duration of a calibration run (normally several weeks long) is within ±0.2%. However, it was recently noticed that BO2 calibration factor experienced sudden changes of close to 1%. The paper will describe several different approaches used for identifying the reason for the observed effect. The investigation has revealed that changes in USCCFM readings are due to the complicated geometry of BO2 feedwater piping and that its accuracy can be as high as a fraction of percent if several readings are averaged around the pipe. (author)

[en] The development of a new Nuclear Operator Training Program provided an opportunity for Ontario Power Generation's Nuclear Training Division to improve the structure the Station Systems courses to meet the needs of Darlington staff. As a result, the training provided is efficient and effective contributing to overall corporate objectives. Following the completion of initial training, including General Employee Training, Science Fundamentals, Safety and Skills Training, all Operators participate in a core group of eight Station Systems Modules. Operators then participate in training specific to a particular duty area (Unit Turbine, Unit Reactor, Unit 0) consisting of four modules each. (author)

[en] Short communication

[en] The Darlington Tritium Removal Facility (DTRF) was originally constructed to help reduce the occupational tritium hazard and environmental tritium emissions at Ontario Hydro Nuclear Generation Stations. The DTRF has also become a vital part of the entire Ontario Hydro Heavy Water Management System. The DTRF product, de tritiated water, reduces the demand for virgin heavy water production at the Bruce Heavy Water Plant. (author). 3 refs., 3 figs

[en] Where we were 2005? In February 2004 a landmark event occurred at Darlington, the powertrack for fueling machine trolley 2 failed catastrophically, resulting in significant damage. This failure resulted in a unit shutdown, significant repair work, and several months of trolley unavailability. Going forward, the Darlington fuel handling system continued to be plagued with frequent equipment reliability issues. Equipment not performing per design challenged unit average zone levels, staff frustration levels, and the completion of planned maintenance. A deteriorating trend was evident as demonstrated by: Frequent equipment breakdowns (>2/week) impacting fuelling capability, and challenging unit average zone levels and operator frustration levels High operator intervention required in semi-auto mode due to frequent operation stops -equipment not performing per design High maintenance frustration - equipment not available to be fixed due to the need to fuel to maintain zone levels Little planned maintenance due to frequent breakdowns- fire fighting mode Large maintenance backlogs relative to station targets By early 2005, confidence in fuel handling equipment was extremely low, a strategy to recover and sustain reliability was vital to our future operation. (author)

[en] This paper describes the design of a mechanism incorporating a rotary magazine to be mounted on a fuelling machine transport trolley for use at a Darlington reactor during a feeder replacement or maintenance outage. The magazine stores reactor channel maintenance components, such as channel isolation plugs and vented closure plugs, in twelve available magazine channels. Use of the magazine rather than a fuelling machine reduces the time required to transfer such components between the Central Service Area and reactor channels. Component transfers are accomplished by locking the fuelling machine onto one of the magazine channels and using a local controller to execute commands received from the fuel handling control system. (author)

[en] Physics simulations in safety analyses are generally performed using a bundle irradiation distribution that is consistent with an approximate time-average configuration. In this paper, three assessments of a spurious adjuster withdrawal event at Darlington are performed with RFSP. The simulations are performed using a time-average irradiation distribution and the SORO predicted irradiation distribution just prior to the actual event. In all three of the assessments it is shown that the results are quite insensitive to the assumed irradiation distribution. This supports the approach of assuming a time-average irradiation distribution in safety analyses. (author)

[en] Flow assisted corrosion (FAC) caused wall thinning has been observed on CANDU feeder pipes. Thinning in general occurs in the first two bends near the Grayloc fitting. In a fitness for service analysis of thinned feeders, the inspected or predicted minimum thicknesses are often used in the stress analysis. The determination of the exact location of the thin spot, axially and circumferentially, is dose intensive during inspection. In view of urgency during an outage to disposition measured thicknesses, two types of stress analysis approaches are developed. Type A analysis, also named here as the 'Average-Minimum-Average' or generic approach provides requirements on minimum wall thickness as well as average wall thickness. The required minimum wall thickness is not location specific and can reside anywhere within the first two bends. It provides great flexibility to disposition feeders with either general or local thinning. On the other hand, Type B analysis is conducted with the exact thickness profile. Type B analysis is performed on feeders which do not pass Type A analysis. The two approaches have been demonstrated in Darlington feeders, where the majority (413 out of 480) of feeders has Type A requirements, while 67 out of 480 have Type B requirements. Type A requirements provide a greater flexibility to disposition local thinning on feeder pipes. (author)

[en] The Darlington nuclear refurbishment program involves distinct projects with a project manager and team. These projects are: re-tube and feeder replacement project; island project; fuel handling project; turbine generator project; boiler and auxiliary systems project; shutdown, layup and services project and balance of plant project.