Radiation Protection during Normal Operation

Radiation protection during normal operation is a fundamental design consideration for the APIOOO, and it is discussed in detail in the EDCD, Chapter 12 (Reference 12.1). Methods incorporated to minimise occupational radiation exposure include core and fuel design, which minimise fundamental radiation sources operational chemistry, which supports excellent fuel performance purification systems shielding automation and overall simplification of the plant. 

This chapter describes the Implementation of the radiation-protection program at the Sandia National Laboratories/New Mexico (SNL/NM) Technical Area V (TA-V) Hot Cell Facility (HCF) under normal or anticipated abnormal operating conditions. Information is included about the HCF facility and equipment design and the planning, procedures, techniques, and practices employed to meet the standards for radiation exposure and protection. A summary of the predicted annual exposures to facility workers (local and collocated) from radiation sources during normal operations is presented. In addition, this chapter describes the responsibilities of specific radiation-protection organizations at SNL/NM. 

This chapter should provide information on the policy, strategy, methods and provisions for radiation protection. The expected occupational radiation exposures during normal operation and anticipated operational occurrences, including measures to avoid and restrict exposure, should also be described. Further discussion on matters to be covered in this chapter of the SAR is provided in Refs [21,23,40,41]. 

To ensure that during normal operation, maintenance and decommissioning, and in emergency situations, the radiation exposure to workers and the public is kept below the dose limits given in the Basic Safety Standards for Radiation Protection (BSS). The standards are set at a maximum of 5 REM annually and a maximum of 3 REM quarterly. 

Although during normal operation of research reactors exposure of the public due to the release of radioactive materials in the environment is expected to be negligible, a site-related assessment of such exposure should be performed prior to operation. The main objective of this assessment is to demonstrate compliance with the system of dose limitation as described in detail in IAEA Safety Series No. 9 "Basic Safety Standards for Radiation Protection 13). These evaluations are normally required by regulatory authorities and include estimating the effective dose equivalent for the most exposed members of the public (critical group) and collective effective dose equivalent commitment of the population ("collective dose"). 

The non-radiator portion of the reactor module envelope aft of the shield must be blanketed in order to keep pre-start-up temperatures above 200 - 250 K with a reasonable amount of heat input. However, excessive blanketing could result in excessive temperatures during normal operation. Preliminary calculations indicate that reducing the effective emissivity below 0.1 to 0.2 could result in excessive temperatures during normal operation. Thus, a balance must be achieved between the normal and pre-start-up thermal requirements. It is possible that micrometeoroid protection could provide the degree of blanketing desired. 

The radiation protection problems which emerge during the operation of a fusion prototype reactor, either in normal or in accident conditions, are essentially connected with the presence of tritium, with the generation of neutrons with energies of 2.45 and 14.1 MeV (derived from the D-D and D-T reactions) and with the delayed radiation (and related thermal decay power), for the activation of the structures of the machine. 

Criterion 19 - Control room. A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents. Adequate radiation protection shall be provided to permit access and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem whole body, or its equivalent to any part of the body, for the duration of the accident. Equipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe condition during hot shutdown, and (2) with a potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures. 

To provide radiation protection of workers from radioactive material operations during normal and abnormal conditions such that exposures to workers in continuously occupied areas of the facility are in accordance with the requirements of 10 CFR 835 (worker safety). 

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