U.S. Nuclear Regulatory Commission

Lower Technical Specification Limit of Detection for Liquid Effluents

HPPOS-171 PDR-9111220193

Title: Lower Technical Specification Limit of Detection

for Liquid Effluents

See the memorandum from L. J. Cunningham to W. D. Shafer

dated December 7, 1987. Technical Specification

requirements on lower limits of detection in effluents

apply to the sampling and analysis systems (equipment and

procedures), not individual samples.

It was found that a licensee's procedures were designed to

detect cesium-134 at the required level in distilled water,

not in a normal effluent sample. This did not meet the

intent of the licensee Technical Specifications on lower

limits of detection for radio-active liquid effluents.

Attempts were made to clarify the requirements on lower

limits of detection (NUREG / CR-4007) but these are still

ambiguous.

The requirements are on the sampling and analysis system

(equipment and procedures) rather than requirements for

individual samples. Licensees are required to have

equipment and procedures that attain the specified lower

limit detection under normal conditions. Therefore, an

occasional failure of an analysis to achieve the specified

lower limit of detection with an actual sample is not a

failure to comply. Repeated failures to achieve the

specified lower limit of detection, however, are indicative

of a system deficiency and do constitute a violation of the

Technical Specifications (TS).

To perform the required measurements, licensees must

account for the presence of various nuclides in the

samples. This may require measures such as increasing the

counting time and/or the use of up-to-date software to

resolve peaks with similar energies. This is indicated in

the TS by requiring the use of "blank samples as

appropriate" for determining the background count rate.

Regulatory references: Technical Specifications

Subject codes: 6.8, 7.3

Applicability: Reactors