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Nuclear powered warships visit planning
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Port visits to Australia by naval vessels of friendly nations, and reciprocal visits by ships of the Royal Australian Navy, are one of the most visible aspects of the defence cooperation between Australia and other countries in peacetime. These naval vessels may be conventionally or nuclear-powered. Ship visits are made with the approval of the Australian Government.
Due to the nature of Nuclear Powered Warships (NPW) propulsion plants, special procedures have been adopted to ensure that the safety of the general public is maintained during visits by such vessels. These procedures include Conditions of Entry and the arrangements for visits, as well as contingency arrangements in the unlikely event of an accident resulting in the hazardous release of radioactivity to the environment.
The nature of these requirements necessitates that responsibility for the conduct of these procedures is shared between Australian Government and state/territory Governments. Australian Government responsibility is generally for international negotiations, prescribing guidelines and approving and arranging visits within those guidelines.
The Australian Government requires contingency arrangements to be in place at all Australian ports visited by NPW and also requires that there be the capability to undertake radiation monitoring of the port environment. These arrangements are formulated to cover two potential release mechanisms, which are failure or malfunction of radioactive waste control systems within the vessel and an accident involving the reactor plant.
The potential for the external radiation exposure of personnel in the vicinity of a NPW at an alongside berth is checked at regular intervals by radiation surveys of areas designated as free for public access. The potential for radiation exposure from the consumption of seafood is kept under surveillance by a program of marine environmental monitoring. Analyses for fission and activation products and any other radionuclide known to characterise radioactive discharges likely to arise from a NPW is conducted on samples of the surface layer of the bottom sediment from the vicinity of the NPW berth or anchorage, and selected local seafood taken from the environs of the berth or anchorage (where possible).
The results of NPW radiation monitoring program are published annually by the Department of Defence. The reports on radiation monitoring for the last five years are provided below:
An inter-departmental committee, the Visiting Ships Panel (Nuclear) (VSP(N)), oversees the arrangements for visits to Australian ports by Nuclear Powered Warships (NPW). These include the Commonwealth Plan OPSMAN1 dealing with visits by Nuclear Powered Warships, and the associated Radiation Monitoring Handbook for Visits by Nuclear Powered Warships to Australian Ports and the Department of Defence document Environmental Radiation Monitoring During Visits by NPWs to Australian Ports: Requirements, Arrangements and Procedures.
The responsibilities of the VSP(N) are to:
- advise the Minister of Defence on proposals for NPW visits
- develop and maintain procedures related to NPW visits
- oversee the implementation of specific arrangements, especially safety requirements, for visits by NPWs.
The Australian planning covering visits by visiting nuclear powered vessels is detailed in OPSMAN1. OPSMAN1 provides detailed information on the conditions, procedures and the responsibilities for the visits by nuclear-powered vessels to Australian ports. Visits are only permitted to Australian ports, which have been assessed and approved as suitable in terms of strict Australian environmental and safety criteria. Conditions of entry to Australian ports by visiting NPW have been established by the Australian Government. In the event of a reactor-based accident, procedures are in place to ensure the early removal of the damaged vessel from the port, thus removing the radiation source term.
Much of the planning for managing potential radiation exposures is based on the modelling results of the Reference Accident. The Reference Accident is a computer model devised for estimating the nature and extent of the radioactive contamination for a severe accident scenario involving a loss of coolant accident in a NPW reactor and the subsequent release of radioactive material to the environment. The Reference Accident is used to assess the acceptability of a port for visits by NPWs and to establish the planning zones for the initial radiation emergency response.
The Reference Accident predicts that, after the passage of the radioactive cloud, the two principal pathways for exposure would be through external irradiation and from ingestion of radioactivity. Resuspension of surface contamination and the subsequent inhalation would be very small. The Reference Accident predicts that the major component of the release would be radioiodine, with the initial levels of Cs-137 contamination predicted to be at least an order of magnitude lower than the initial radioiodine levels. Both Cs-137 and radioiodine contamination can move easily into the environment, and this implies that all foodstuff produced in the affected area, particularly milk would need to be monitored closely to ensure that the radiation dose to critical members of the public is minimised.
For the purposes of Australian NPW emergency planning, the radiological consequences of a severe hypothetical accident scenario are calculated and compared with radiological acceptance criteria. The hypothetical accident, termed the Reference Accident, is selected to represent an upper bound risk to the surrounding population, and is used to assist in planning emergency arrangements. The use of such a Reference Accident is also the basis for estimating the adequacy of emergency planning for any research reactor sites in Australia. The aim of the Reference Accident is to aid in planning emergency measures that would take effect if an accident occurred on a visiting NPW, and involved the release of radionuclides from the nuclear reactor on these vessels.
The calculated consequences of this scenario are compared with port acceptability criteria to determine, on a port specific basis, whether the impact of the Reference Accident on the surrounding population meets the criteria. In addition, emergency planning zones based on the calculated consequences of the Reference Accident are used by emergency planning authorities in developing port specific emergency arrangements.
The guidelines in OPSMAN1 require suitable radiation-monitoring programs to address two situations, routine environmental monitoring and emergency monitoring related to a reactor accident. Conditions of Entry for nuclear-powered warships (NPW) require that, for the port being visited, there be an operating safety organisation, competent to conduct a suitable radiation monitoring program and able to initiate actions and provide services necessary to safeguard the public in the event of a release of radioactivity following a reactor accident. The organisation is to be well practised and capable of quick and effective action.
For each NPW visit routine environmental radiation monitoring program is conducted to provide means for:
- confirming no release of radioactive material or emission of ionising radiation
- determination of the nature and extent of any releases/emissions
- assessing the levels of radiation and any contamination in the environment around the NPW.
The potential for the external radiation exposure of personnel in the vicinity of a NPW at an alongside berth is checked at regular intervals by radiation surveys of areas designated as free for public access. The potential for radiation exposure from the consumption of seafood is kept under surveillance by a program of marine environmental monitoring. Sensitive, high volume seawater monitoring and analyses in the vicinity of the berth or anchorage are undertaken before and after visits to test environmental impacts.
A radiation monitoring system is available during each NPW visit to provide early detection of a reactor accident of sufficient severity to possibly cause a major release of fission products to the environment. This early warning system is complemented by arrangements for notification by the NPW should an accident occur.
ARPANSA, the Australian Nuclear Science and Technology Organisation (ANSTO) and the Australian Defence Forces (ADF) are the main Commonwealth agencies providing radiological support to the emergency plans. The coordination of the Australian Government response is the responsibility of Emergency Management Australia (EMA).
The immediate monitoring response to a NPW accident is provided by local Radiation Monitoring Groups, comprising State radiation health, emergency services personal or navy reservists under the direction of an ANSTO health physicist. ARPANSA provides TLD monitors, analyses marine samples and in event of a NPW accident it would provide additional teams and the Commonwealth Technical Advisor to support the State response through the COMDISPLAN.
The objectives for the conduct of emergency radiation monitoring for NPW visits are to:
- provide accurate and timely data on the level and degree of hazards resulting from the release
- provide detail of the physical and chemical characteristics of the hazard
- determine the extent and duration of the hazard
- assist decision makers on the need to take protective actions and interventions on the basis of operational intervention levels (OILs)
- confirm the efficiency of remedial measures such as decontamination procedures
- assist in preventing the spread of contamination
- provide information for accident classification
- provide information for protection of emergency workers
More extensive monitoring of affected areas is conducted following the immediate post accident monitoring. This could continue for several days, weeks or months, depending on the extent of the release. The ARPANSA Environmental Monitoring Handbook for Visits by Nuclear Powered Warships Part A Monitoring for Post Accident Recovery aims to address these objectives in the context of a radiation release associated with a visiting Nuclear Powered Warship in an Australian port. It provides the recommendations on procedures for sample collection and analysis and the basis for the training of the relevant monitoring teams.
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