Surveillance reactors

Nuclear power has achieved an excellent safety record. Exceptions are the accidents at Three Mile Island in 1979 and at Chernobyl in 1986. In the United States, safety can be attributed in part to the strict regulation provided by the Nuclear Regulatory Commission, which reviews proposed reactor designs, processes appHcations forUcenses to constmct and operate plants, and provides surveillance of all safety-related activities of a utiUty. The utiUties seek continued improvement in capabiUty, use procedures extensively, and analy2e any plant incidents for their root causes. Similar programs intended to ensure reactor safety are in place in other countries. 

Laser stimulation of a silver surface results in a reflected signal over a million times stronger than that of other metals. Called laser-enhanced Raman spectroscopy, this procedure is useful in catalysis. The large neutron cross section of silver (see Fig. 2), makes this element useful as a thermal neutron flux monitor for reactor surveillance programs (see Nuclearreactors). 

Woodruff, E.M., Graphite surveillance in N reactor. In Proceedings of the IAEA Specialists meeting on the Status of Graphite Development for Gas Cooled Reactors, IAEA-TECHDOC-690, IAEA, Vienna, 1993. pp. 273 280. 

Kahn, B., Blanchard, R. L., Krieger, H. L., Kolde, H. E., Smith, D. B., Martin, A., Gold, S., Averett, W. J Brinck, W. L. and Karches, G. J. (1970). Radiological Surveillance Studies at a Boiling Water Nuclear Power Reactor, Report No. BRH/DER-70-1, also Report No. PB-191091 (Bureau of Radiological Health, Rockville, Maryland). 

A fit-for-purpose estimate of the individual activities is needed for waste disposal purposes and calculation of neutron activation of precursors is often the simplest method, where contamination is unimportant. For H, the concentration of the Li precursor is required. The mobile nature of is a complicating factor since, in principle, it may remain in situ or diffuse within the bulk material. The aim of this work was to provide some answers to the above questions by determining the concentrations of Li in reactor steels and to compare the predicted levels of with values measured in reactor surveillance specimens. Preliminary attempts to measure Li in reactor steels by ICP-OES (inductively coupled plasma - optical emission spectroscopy) were not successful and... 

The radiochemical analysis for of RPV surveillance specimens, neutron activated in reactor, was straight forward and allowed the effective precursor Li concentration to be... 

The concentration of natural lithium (tritium-precursor) in un-irradiated Magnox RPV steel has been estimated directly using SIMS-MS and SEM-EDX and indirectly from measuring tritium induced by neutron activation of mainly Li. Tritium was measured in surveillance specimens irradiated during the 26 year operational life of a Magnox reactor followed by radioactive decay of approximately 15 years. For comparison purposes, inactive archive RPV steel was also irradiated in the CONSORT reactor followed immediately by radioanalysis for tritium. In this way, the possibility of diffusive transfer of tritium into or out of the steel during residence in the reactor could be evaluated. 

Solid radioactive wastes are produced from many systems and purification circuits of the reactor station, see Figure 20.7. Many contaminated items can be decontaminated by proper treatment, saving both money and waste storage space. Low level waste can also sometimes be "declassified" and disposed of as normal, inactive, waste or scrap. Combustible solids may be reduced in volume through incineration. Several techniques are used for fixation of wastes in such a way that they can be safely stored with a minimum of surveillance. These techniques all have in common an enclosure of the activity in an insoluble material (normally concrete or bitumen) and in blocks of sizes and activities small enough to be handled with a fork lift. 

Johnson, J. E. Johnson J. A. "Radioactivity Analyses and Detection Limit Problems of Environmental Surveillance at a Gas-Cooled Reactor" - Chapt. 14 in this volume. 

The demands related to the prolonged operation of the PHENIX reactor have led us to focus on hypothetical defects which, in the various operating conditions envisioned, might question the principle safety functions, and among these, the control of the reactivity. Therefore the extension of such defects, penetrating the great shells which make up the core support structure, had to be evaluated. In order to facilitate their early detection, the geometric disorders associated with much shorter defects constituted another point of interest in the specification of surveillance methods. 

Inspection intervals (10 years) for ASME Section XI components are shown in Table 3.9-3. Material surveillance inspection intervals for ASME Section XI are shown in Table 3.9-4. Material surveillance will be done on material samples removed from the reactor. Inspection intervals for IEEE surveillance will be established in accordance with the applicable IEEE standards. 

GA Technologies, Inc. (GA). Nuclear Island ISI Surveillance Assessment, Modular High-Temperature Gas-Cooled Reactor. HTGR-86-026. GA, San Diego, CA, May 1986, Draft. 

Structures, systems and components important to safety vhich are installed as redundant items, or are called upon when normal operating conditions are threatened or lost, are normally kept in standby or off-line states. Examples of such SSCs are reactor containment vessels, emergency electric power sources, isolation valves and safety valves. Some of these SSCs cannot be monitored in situ for their operating reliability. Testing and surveillance for the actual conditions under which they are expected to operate, and which are generally difficult or impossible to reproduce, are usually undertaken under simulated conditions. These simulated conditions should be carefully planned, and the results should be interpreted prudently. 

The risk assessment should cover in particular those activities that have a significant influence on the level of risks at the plant, for example, mid-loop operation of a pressurized water reactor. Use should be made of the results of probabilistic safety assessments for the shutdown mode if these are available. Any specific training needs, special procedures for the shutdown mode or additional operating procedures or surveillance necessary should be identified in the risk assessment. 

Surveillance measures that should be taken to verify the integrity and assess the residual service life of the pressure boundary for the primary reactor coolant include, but are not necessarily limited to ... 

The surveillance of safety systems should cover systems and components provided to shut down the reactor and keep it shut down, and to ensure that safety limits are not exceeded either owing to anticipated operational occurrences or during the initial operation of systems that are required in order to mitigate the consequences of accident conditions. Such mitigation could be done through ... 

An appropriate material surveillance program for the reactor vessel,... 

Code of Federal Regulations, Title 10, Part 50, Appendix H, "Reactor Vessel Material Surveillance Program Requirements."... 

Closed circuit television equipment is used for general surveillance and for the examination of core restraint structures. Normally 2/3" newvicon cameras are used but for increased sensitivity 1" cameras can be employed. The cameras are modified on-site to be gas-cooled and to permit manipulations between the core and the pressure vessel. All the reactors are surveyed during their annual refuelling outages and no noticeable lens darkening has been encountered even after several hours continuous operation. 

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