Relaxation of Definition of Source Check in Reference to Effluent Radiation Monitors
See the memorandum from L. J. Cunningham to J. H. Joyner (and others) dated December 6, 1990.
This memo states that any proposal by a licensee to relax the definition of a source check is not acceptable without compensatory measures to maintain overall effluent control for the proposed relaxation.
A licensee had submitted an amendment request to move the existing procedural details of the current Radiological Effluent Technical Specifications (RETS) to the Offsite Dose Calculation Manual (ODCM). The licensee, as well as twenty-two other facilities, used plastic scintillator / photomultiplier type effluent radiation monitors that contained either a built-in LED light source or a secondary check source that did not expose the primary detector. These alternative source check measurements were used to meet the monthly qualitative source check requirement. The definition of "source check" under the Technical Specifications requires that the channel sensor, including the primary radiation detector, be exposed to a radioactive source.
The licensee's amendment request would not change the definition for source check; however, if the amendment were approved, the licensee would be free to relax the definition for source check under its ODCM, provided they met the criteria that "the over-all level of radiological effluent control is not reduced." A violation of this criteria would be a violation of the licensee's Technical Specification.
The NRR staff have adopted the position that any proposal by a licensee to relax the definition of source check, whether through an amendment request or under its ODCM pursuant to Generic Letter 89-01, is not acceptable without the licensee providing compensatory measures for the proposed relaxation. This is necessary because such changes on measurements can reduce the overall effluent control. Therefore, the following conditions must be met:
If the detector of concern is used as the primary means of quantifying radionuclides in effluent streams, the licensee must proved justification on why an alternative and technically more accurate measurement (e.g. taking grab samples) is not available. If an alternative measurement is not available, then detector specific and other effluent-related information should be provided either in the ODCM or other means for the staff to evaluate whether the overall effluent control will be reduced.
If the scintillator plastic / photomultiplier type detector is used only for detecting radiation that activates the alarm / trip setpoint, relaxation of the current source check definition should be accompanied by a commitment from the licensee to provide compensatory measures to ensure the overall effluent control not be reduced over time and usage. A commitment by the licensee to Cross-check and Document the detector scaler count-rate with the grab sample result (C&D measurement), where practical, in lieu of the monthly source check measurement, would be acceptable. In those situations where the C&D measurement or other comparable measurements are not practical, the use of the LED light source and/or secondary check source measurements would be acceptable.
Regulatory references: 10 CFR 50, Regulatory Guide 1.21, Regulatory Guide 4.15, Technical Specifications
Subject codes: 6.6, 7.3, 12.12