ML20235U376
| 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: |
| References | |
| 50-416-88-27, NUDOCS 8903090174 | |
| Download: ML20235U376 (1) | |
See also: IR 05000416/1988027
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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
after transient equilibrium, the activity decreases with an " apparent
i
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
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the floor drain collector tank samples. The inspector noted that approved
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8903090174 890227
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ADDCK 0500
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