ML20235U376

Corrected Page 4 to Insp Rept 50-416/88-27

ML20235U376
Person / Time
Site:	Grand Gulf
Issue date:	02/27/1989
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20235U347	List: ML20235U345 ML20235U376
References
50-416-88-27, NUDOCS 8903090174
Download: ML20235U376 (1)

See also: IR 05000416/1988027

Text

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from 10 t'o 20 percent. The licensee was planning to replace one of the.

detectors during 1989. The count room also contained two NMC gas flow

proportional counters for alpha / beta detection, two- sodium iodide well

counters for gross gamma determinations and one Packard Tri-Carb liquid

scintillation counter for tritium and iron-55 analyses.

Staffing for- the Chemistry Department totalled 37 positions , including

supervisors.and staff. Currently seven positions were vacant, and two of

the seven vacancies were not considered necessary to maintain chemistry

operations and were not going to be filled. Reorganization of. the

department during January 1989 would have the Plant Chemist reporting

directly to the Manager of Plant Operations rather than -the Control

Superintendent.

No violations or deviations were identified.

6. Confirmatory Measurements (84750)

Reactor coolant and selected liquid and gaseous effluent streams.were

sampled by the licensee and analyzed for isotopic concentrations using the

licensee's gamma spectroscopy systems and the NRC Region Il mobile

laboratory. The purpose of these comparative measurements was to verify

the licensee's capability to accurately measure gamma radionuclides

concentrations in various plant systems and effluent streams. Comparisons

were'made utilizing the licensee's four detectors in the chemistry count

room. Sample types and counting geometries included the following:

reactor coolant system - 100 ml diluted in a 1000 m1 liquid Marinelli;

liquid waste collection tank - 1000 mi liquid Marinelli; retreatment

offgas - 14cc gas vial; and retreatment offgas - 4300cc gaseous Marinelli.

Spiked charcoal cartridge and particulate filter samples were provided in

lieu of. licensee samples which did not have sufficient activity for

comparisons.

Comparison of licensee and NRC results are listed in Attachment I with the

acceptance criteria listed in Attachment 2. The results showed agreement

for all geometries with the exception of one isotcpe, Tc-99m, for the

liquid samples. The disagreement resulted from the licensee's use of the

Mo-99 half-life value to calculate Tc-99m activities. Mo-99 has a

half-life of 66.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> and decays into Tc-99m, which has a half-life of

6.02 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Both isotopes can be identified from the 140 kev peak. Prior

to transient equilibrium, Tc-99m decays with the 6.07 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> half-life and

i after transient equilibrium, the activity decreases with an " apparent

half-life" equal to the half-life of Mo-99. Recalculation of the

licensee's Tc-99m activity using the Tc-99m half-life showed agreement for

all samples. The licensee agreed to alter their nuclide library to use the

shorter half-life for the Tc-99m activity calculations. Count room

personnel were also considering an upgrade of the current nuclide software  !

which would provide calculations for spectrum stripping and could therefore

quantify Mo-99 from secondary peaks.

The inspector observed collection of the retreatment offgas sample and  !

the floor drain collector tank samples. The inspector noted that approved

"

8903090174 890227 6

DR ADDCK 0500