HJ 1056-2019Analytical method of 14C in liquid effluent of nuclear power plant -- Wet oxidation (English PDF)

1 National Environmental Protection Standard of the People's Republic of China

Analytical method of 14C in liquid effluent from nuclear power plant-Wet oxidation Analytical method of 14C in liquid effluent of nuclear power plant

--Wet oxidation

Published on October 25, 2019 2019-11-15 Implementation Ministry of Ecology and Environment i table of contents Foreword ... I

1 Scope ... 1

2 Normative references ... 1

3 Methodology ... 1

4 Reagents ... 2

5 Equipment and materials ... 2

6 Sample Collection and Storage ... 2

7 Analysis steps ... 2

8 Calculation and Representation of Results ... 3

9 Precision and accuracy ... 5 Appendix A Schematic of Sample Preparation Device ... 6 I foreword in order to implement the "Environmental Protection Law of the People's Republic of China" Republic Nuclear Safety Law, which regulates the analysis method of 14C in liquid effluent from nuclear power plants, and formulated this standard.

This standard specifies the 14C analysis method-wet oxidation method for liquid effluent from nuclear power plants.

This standard is issued for the first time.

This standard is formulated by the Department of Nuclear Environment Safety Supervision, Regulations and Standards of the Ministry of Ecology and Environment.

2 Normative references

The content of this standard refers to the following documents or clauses therein. For undated references, the valid version is Used in this standard.

GB/T 6682 Analytical laboratory water specifications and test methods GB 11217 General requirements for monitoring effluent from nuclear facilities HJ 493 Technical regulations for the storage and management of water samples

3 Method principle

24 Reagent

Unless otherwise specified, the reagents used in this standard use analytical and purification reagents that meet national standards.

The water is not lower than GB/T 6682 secondary water or water of equivalent purity.

4.1 Sodium persulfate solution. 100g/L.

4.2 Phosphoric acid solution. The volume fraction is 5%.

4.3 Alkali absorption solution. 1mol/L sodium hydroxide solution, or organic lye.

4.4 14C reference materials. 14C labeled n-hexadecane and Na214CO3.

4.5 Toluene (C6H5CH3).

4.6 Triton X-100 [C8H17 (C6H4) (OCH2CH2) 10OH].

4.7 2,5-Diphenyloxazole [OC (C6H5) = NCH = CC6H5]. PPO for short, pure flicker.

4.8 1,4- [Bis- (5-phenyloxazole-2)] benzene, ([OC (C6H5) = CHN = C] 2C6H4). referred to as POPOP, flickering pure.

4.9 scintillation fluid.

-Use toluene (4.5) and Triton X-100 (4.6) to mix at a ratio of 2 1. Weigh out 4.00g of PPO (4.7) and 0.30g POPOP (4.8) were dissolved in 1000 ml toluene-triton X-100 mixed solution and transferred to brown reagent Store the bottles juxtaposed in a dark place. The scintillation fluid should be used immediately.

-You can also use the commercial scintillator directly.

5 Equipment and materials

5.1 For an example of a sample preparation device, see Appendix A. The total organic carbon analyzer 2 can also be used as a sample preparation device.

5.2 Analytical balance. The accuracy is 0.1mg.

5.3 Brown glass bottle. 1L, used to store water samples, need to be dried before use.

5.4 Pipette. 1ml, 5ml graduated pipette.

5.5 High-purity nitrogen. purity >=99.99%.

5.6 Liquid flash counting bottle. 20ml.

5.7 Low background liquid scintillation counter. background <= 2cpm.

5.8 Glass absorption bottle. 50ml or 100ml.

6 Sample collection and storage

6.1 The collection and storage of samples shall be performed in accordance with the relevant regulations of HJ 493 and GB 11217.

6.2 When collecting samples, the samples should be filled in brown glass bottles and filled, leaving no headspace, and protected from light.

6.3 The collected water samples shall be determined within 24 hours.

7 Analysis steps

7.1 Clean the sample preparation device with pure water for later use.

7.2 Check the air tightness of the sample preparation device (5.1) by introducing nitrogen.

7.3 Continue to introduce nitrogen (5.5) at a flow rate of 30 ml/min to 50 ml/min until the preparation of the carbon dioxide absorption solution is completed.

Optional commercial TOC analyzer.

37.4 Add 20 ml of alkaline absorption solution (4.3) to a glass absorption bottle (5.8).

7.5 Add 60.0ml (V1) water sample to the reactor. If suspended matter exists in the water sample to be tested, first use a 0.45µm filter membrane Filter.

7.6 Add 20 ml of phosphoric acid solution (4.2) and 20 ml of sodium persulfate solution (4.1) to the reactor.

7.7 Heat the liquid in the reactor and control the temperature at 95 ± 3 ° C to maintain a sufficient reaction time3.

7.8 Purge the carbon dioxide gas generated during the reaction with nitrogen, and dry the alkali absorption into the glass absorption bottle.

The liquid was collected to produce a carbon dioxide absorbing solution (V2).

7.9 Transfer 8.0ml (V3) carbon dioxide absorption liquid to the liquid scintillation counting bottle (5.6), add 12.0ml scintillation liquid (4.9), Tighten the bottle cap and shake well to make the sample 4 to be tested. The samples to be tested should be kept away from light.

7.10 Replace the test water with a calibration water sample prepared with a 14C reference material and having an activity concentration close to the 14C activity concentration in the effluent.

In accordance with the methods and steps of 7.1 to 7.9 above, prepare a calibration sample.

7.11 Use deionized water as a blank water sample instead of the water sample to be tested, and prepare blank samples according to the methods and procedures of 7.1 to 7.9 above.

7.12 Use a low background liquid scintillation counter to measure the test sample (7.9), the calibration sample (7.10), and the blank sample (7.11) in this order.

7.13 Counting efficiency scale and quench correction Using Na214C03 (4.4) and sodium hydroxide solution (4.3) to establish a quenching correction working curve for liquid scintillation counting5, the counting efficiency after quenching correction is obtained according to the quenching curve.

8 Results calculation and representation

8.1 Conversion-absorption efficiency Calculate the conversion-absorption coupling based on the count rate of the calibration sample, the activity concentration of the calibration water sample used to prepare the calibration sample, etc.

Total efficiency.

ECV

NN b xxx

Where. xi-transformation-absorption joint efficiency Ns-Counting rate of calibration sample, cps;

Nb- blank sample count rate, cps;

V1-The volume of the calibration water sample used to prepare the calibration sample, ml;

V2-Total volume of carbon dioxide absorption solution, ml;

The volume of carbon dioxide absorption liquid added to the V3-liquid scintillation counting bottle, ml (take 8.0ml in this standard);

If you use a total organic carbon analyzer as the sample preparation device, set the time by referring to its instructions; if you set up the device yourself, 30 minutes is recommended.

For the ratio of carbon dioxide absorption liquid to scintillation liquid, this standard recommends but does not limit the ratio to 8.12. However, care should be taken to prepare blank samples, when calibrating the sample and the sample to be tested, the ratio of the carbon dioxide absorption liquid to the scintillation liquid must be the same.

Establish the quenching calibration working curve to use the chemical solution system consistent with the measured sample as much as possible.

4Es-Counting efficiency of the calibration sample (after quenching correction),%;

C- Activity concentration of the calibration water sample used to prepare the calibration sample, Bq/ml.

8.2 The formula for calculating the activity concentration of 14C is.

kNN

A b xxx

Where. A- activity concentration of the water sample to be measured, Bq/L;

Nlambda-counting rate of sample to be tested, cps;

Nb- blank sample count rate, cps;

V1-Volume of water sample to be used for preparing the test sample, ml;

V2-Total volume of carbon dioxide absorption solution, ml;

The volume of carbon dioxide absorption liquid added to the V3-liquid scintillation counting bottle, ml (8.0ml recommended in this standard) xi-transformation-absorption joint efficiency;

Elambda-Counting efficiency of the test sample (after quenching correction),%;

k-unit conversion factor, 1000ml/L.

8.3 Lower detection limit of the method Calculation of lower detection limit of this method.

kTNK

LLD b xxxx

In the formula. LLD-lower detection limit, Bq/L;

K-confidence coefficient (1.645, 95% confidence);

Nb- blank sample count rate, cps;

T- measurement time of the sample to be tested, s;

xi-transformation-absorption joint efficiency%;

Elambda-counting efficiency (after quenching correction),%;

V1-Volume of water sample to be used for preparing the test sample, ml;

5V2-Total volume of carbon dioxide absorption solution, ml;

V3-Volume of the carbon dioxide absorption solution added to the liquid scintillation counting bottle, ml;

k-unit conversion factor, 1000ml/L.

Absorbed in 1mol/L sodium hydroxide absorbent, under typical analysis conditions (Nb = 0.66cps, T = 5400s, xi = 63%, Elambda = 62%, V1 = 20mL, V2 = 60ml, V3 = 8mL), LLD = 0.7Bq/L.

9Precision and accuracy

9.1 Precision

Six laboratories performed uniform samples with 14C activity concentrations of 14.2Bq/L, 142.9Bq/L, and 1226.8Bq/L Determination.

Relative standard deviations in the laboratory were. 2.13% to 15.31%, 1.84% to 8.16%, and 0.6 to 3.33%;

The relative standard deviations among laboratories were 4.4%, 5.6%, and 5.5%;

Repeatability limits are. 2.98 Bq/L, 15.91 Bq/L and 68.04 Bq/L;

Reproducibility limits are. 3.22 Bq/L, 25.95 Bq/L and 195.55 Bq/L.

9.2 Accuracy

Six laboratories unified samples with 14C spiked activity concentrations of 10Bq/L, 100Bq/L, and 1000Bq/L Determined.

Spike recovery rates were 47% to 79%, 64% to 80%, and 43% to 82%;

Final spiked recoveries. 68% ± 23%, 69% ± 12% and 67% ± 26%.

6 Appendix A Schematic of Sample Preparation Device (Informative appendix) Explanation.

1- Alcohol lamp (heating device);

2-round bottom flask (reactor);

3- Pass in nitrogen (carrier gas);

4- glass funnel (injector for adding phosphoric acid solution and sodium persulfate solution);

5- thermometer

6-condensation tube;

7- drying device;

8-Glass absorption bottle, can be connected in series in multiple stages;

9- ice water bath device.