1. Additional Operating Chemistry Considerations
Presented To:
KEPRI & KHNP
Presented By:
Dr. Robert Litman 1

2. Laboratory Chemical Analysis
Gas Chromatography
Ion Chromatography
Inductively Coupled Plasma/Atomic Absorption
Titrimetry
Miscellaneous pH
Conductivity
NPOC
Ammonia

3. Calculation and Measurement of Hydrogen in RCS(Strip Gas Method)
Entire vessel initially evacuated
RCS liquid is introduced while under vacuum.
Liquid is shaken to improve degas
Argon bubbled into vessel bring pressure close to atmospheric (pressure gage required on vessel). Alternatively, the upper valve can be opened to achieve atmospheric pressure.
Gas syringe is used to sample through gas septum.
Gas is analyzed on GC as %H2.
septum
Gas space
Pwater + PHydrogen
Argon purge line
RCSliq

4. Calculating Hydrogen in the RCS
H2, cc/kg = %H2*Patm *Vg + VH + VG
[100*760] [MS] []
Where Patm = final pressure of sample vessel, mm of Hg
Vg = volume of gas space of bomb, in cc
VH = volume of sample removed for hydrogen analysis, in cc
Vg = volume of sample removed for radioactive gas analysis, in cc
Ms = mass of sample, in g
880 = correction factor cc/kg * [PSTP-PH2O] * TSTP
PSTP [TSTP + TH20]
15.9 = solubility of H2 at STP with pure H2 gas phase

5. Orbisphere Cell Diagram

6. Hydrogen by Gas Membrane
Diffusion
Thermal conductivity Detection
Purge gas
Rate of change measurement
A gas-sensing technique combines a gas diffusion membrane with a unique solid-state gas thermal conductivity detector operating in a dynamic mode. The small volume enclosed between the diffusion membrane and the thermal conductivity detector is periodically flushed with a purge gas. After each purge cycle, the thermal conductivity of the gas surrounding the detector gradually changes from the value of the purge gas to that of the gas of interest, due to the gas of interest’s inflow.
The rate of change of the thermal conductivity is continuously monitored and is a direct function of the concentration of the gas to be measured.

7. Hydrogen – Analytical Problems
Recently one plant began to detect elevated levels of hydrogen in the RCS and VCT. As a result of the analytical values they reduced the VCT H2 pressure.
The hydrogen concentration did not decrease.
Why?

8. Hydrogen – Analytical Problems (continued)
It is important to note that He provides significant interference in the analysis of hydrogen by gas membrane. He has a very high heat capacity (like hydrogen) and the membrane cannot distinguish the two gasses.
The plant with high hydrogen had not been venting their VCT and He gas began to build up (what is the source of He?).
Gas chromatographic analysis of the VCT gas resolved the issue and the VCT was vented. However the true hydrogen concentration of the RCS had dropped to ~18 cc/Kg in the interim.
The GC analysis at first was thought to be incorrect. The plant kept reducing VCT H2 pressure and nothing changed.

9. Oxygen Diffusion through membrane
Electrochemical reaction creates a voltage which is proportional (via Nernst Equation) to a concentration of oxygen.
O2 + 2H2O + 4e-  4OH-
2Ag0 + 2OH-  Ag2O + H2O + 2e-
Fouling of the electrode can cause erratic readings to occur
Oxygen gas diffuses through a membrane and is electrochemically reduced in a solution surrounded by an anode and cathode. The current of the reduction process is measured continuously and this is proportional to the concentration of oxygen in the flowing stream.

10. Ion Chromatography Sample Matrix Instrument parameters
Boron concentration can affect elution characteristic of anions (especially F-)
Consideration should be given for a high and intermediate boron calibration curve as matrix
Instrument parameters
Eluent concentration
Guard column bleed
Analytical column degradation

11. Inductively Coupled Plasma (ICP) and Atomic Absorption
Instrument response for a fixed concentration of metal ion should be constant
Corrosion product Metals analysis for Cr, Ni, Fe, and Mn(Weekly)
Contaminant analysis for Al, Mg, Ca (Quarterly)
Chemical additives analysis for Li, Zn (daily)
Many of the elements above exhibit matrix effects which need to be accounted for
Pre-concentration by volume reduction can assist in achieving desired detection levels

12. Sources of Error/Discrepancy in Chemical Analyses
Matrix effects (especially if a power change has occurred)
Adequacy of sample flush
Sample line representativeness
Contamination of equipment
Recent system upsets unknown to the analyst
Maintenance activities
Electrical line conditioning

13. Hydrogen and Oxygen Analysis Using an Orbisphere

14. Primary Chemistry Sample Sink