Contamination of Nonradioactive System and Resulting Potential for Unmonitored, Uncontrolled Release of Radioactivity to the Environment
See IE Bulletin No. 80-10 entitled as above and dated May 6, 1980. Action Item 3 of this bulletin states that if a nonradioactive system becomes contaminated and it is considered necessary to continue operation, an immediate safety evaluation must be performed in accordance with 10 CFR 50.59.
An auxiliary boiler had been operated for an extended period of time with contaminated water containing up to 2x10-2 micro-Ci/ml. The contamination was caused by a tube leak in a temporary hose connecting the auxiliary boiler to a radioactive waste evaporator concentrate tank. Upon cooling and condensation of steam in the hose, contaminated water siphoned from the concentrate tank back to the auxiliary boiler. Because of additional and continuing leaks in the heat exchanger of the waste evaporator, the licensee's efforts to decontaminate the auxiliary boiler feedwater were ineffective.
Maintenance of proper boiler chemistry was difficult because blowdown options were restricted due to contamination. As a result, 100 mCi of radioactive material were released off-site in steam via the auxiliary boiler fire box and smokestack. The release resulted in increased environmental levels of cesium and activation products being detected eight miles downwind from the site boundary.
Actions to be taken by licensees with operating licenses to preclude the described situation include:
Review facility design and operations to identify systems considered as nonradioactive (or described as nonradioactive in the FSAR) that may become contaminated by radioactive systems. Consideration should be given to the following: auxiliary boiler system, demineralized water system, isolation condenser system, PWR secondary water clean-up system, instrument air system, and sanitary waste system.
Establish a routine sampling / analysis program for these systems to detect radioactive contamination.
If nonradioactive systems are or become contaminated, further use of the system shall be restricted until the cause is identified, corrected, and decontaminated. However, if it is considered necessary to continue operation with the contaminated system, an immediate safety evaluation of the operation of the system as a radioactive system must be performed in accordance with the requirements of 10 CFR 50.59. The 10 CFR 50.59 safety evaluation must consider the level of contamination and any potential releases of radioactivity to the environment. The relationship of such releases to the radioactive effluent limits of 10 CFR 20 [§§20.1001-20.2401], the facility's Technical Specifications, and to the environmental radiation dose limits of 40 CFR 190 must also be evaluated. The record of the safety evaluation must set forth the basis and criteria on which the determination was made.
If it is determined in the 10 CFR 50.59 safety evaluation that operation of the system as a radioactive system is acceptable, provisions must be made to comply with the requirements of 10 CFR 20.201 [or, at present, 10 CFR 20.1501], General Design Criterion 64 to 10 CFR 50, Appendix I to 10 CFR 50, and the facility's Technical Specifications. Specifically, any potential release points must be monitored and all releases must be controlled and maintained to ALARA levels described in 10 CFR 50 Appendix I and within the corresponding environmental dose limits of 40 CFR 190. If in the 10 CFR 50.59 determination it is concluded that operation of the system as a radioactive system constitutes an unreviewed safety question or requires a change to the Technical Specifications, the system shall not be operated as contaminated without prior commission approval.
Regulatory references: 10 CFR 50.59
Subject codes: 5.0, 7.3, 9.2