NB/T 20018-2010Containment Leak Tightness Test for Nuclear Power Plants (English PDF)

3.1 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1.1 leakage

amount of fluid lost from a leak (hole, opening, crack, etc.)

3.1.2 leakage rate

leakage per unit time, which is expressed as the rate of fluid loss from the test vessel under the specified test pressure

3.1.3 overall integrated leakage rate

total leakage rate through all the tested leakage pathways, including the entire pressure boundary such as the containment welds, blind plates, valves, penetrations and joints, which is expressed as a percentage of the ratio of the mass of air leaked into the atmosphere from the containment within 24h under the test pressure to the initial mass of air contained in the free volume inside the containment

3.1.4 maximum pathway leakage rate (MXPLR)

maximum leakage rate via the leakage pathways of penetrations, which is the larger value of the leakage rate between two boundaries in series

3.1.5 minimum pathway leakage rate (MNPLR)

minimum leakage rate via the leakage pathways of penetrations (for example, the smaller leakage rate between the inner and outer boundaries), which is half of the measured total leakage rate when pressure is applied between the inner and outer boundaries

3.1.6 acceptance criteria

criteria to be met for test results in order to verify the sealing function of containment as a pressure boundary

3.1.7 verification test

test to verify the feasibility of Class A test methods and the reliability of test apparatuses for overall integrated leakage rate

3.2 Symbols

3.2.1

The following symbols apply to this document.

Pac - - the peak pressure generated in the containment corresponding to the design basis accident, which is usually specified in the design technical documents, MPa;

Pd - - the design pressure of containment, which is usually specified in design documents, MPa;

La - - the maximum allowable overall integrated leakage rate when the pressure inside the containment is Pac under the test conditions, which is usually specified in the technical documents, %/24h;

Lam - - the best estimate of the overall integrated leakage rate of containment obtained from the test on containment under a pressure Pac when the equipment and systems in the containment are as close as possible to the design basis accident state, %/24h;

Lo - - the known leakage rate superimposed on the containment during the verification test, %/24h;

Lc - - the overall integrated leakage rate of containment after Lo is superimposed, %/24h;

UCL - - the upper confidence limit, which is the statistical calculation upper limit of the best estimate of overall integrated leakage rate from containment, and is calculated at a 95% confidence level in this standard.

3.2.2

The following symbols only apply to Annex A.

P - - the absolute pressure of air in the containment, MPa;

PV - - the weighted average partial pressure of water vapor in containment, MPa;

R - - the specific gas constant of dry air, 287.0J/(kg·K);

Ti - - the weighted average temperature of air in containment corresponding to the ith set of data, K;

V - - the volume of free space in the containment, m3;

Wi - - the dry air mass in containment corresponding to the ith set of data, kg;

- - the best estimate of linear regression Wi, kg;

ti - - the time elapsed from the reference time of the beginning of measurement to the ith set of data, h;

A - - the slope of the least squares regression line, kg/h;

B - - the intercept of the least squares regression line, kg;

n - - the number of measurement data sets (ti, Wi);

SA - - the unbiased estimate of standard deviation of linear regression slope with the least squares method, i.e., the uncertainty component of Class A evaluation, kg/h;

- - the ith standard uncertainty component of Class B evaluation;

uc - - the combined standard uncertainty;

U95rel - - the relative expanded uncertainty at a 95% confidence level.

3.2.3

The following symbols only apply to Annex B.

Ll - - the gas leakage rate, NL/min;

L_l^' - - the water leakage rate, L/min;

P1, P2 - - respectively the absolute pressure at the beginning and end of the test, kPa;

P_1^', P_2^' - - respectively the absolute pressure of upstream and downstream water, kPa;

PS - - the atmospheric pressure at the standard state (0.101325MPa), MPa;

µ' - - the viscosity of water, Pa·s;

µ - - the viscosity of air, Pa·s;

T1, T2 - - respectively the ambient temperatures at the beginning and end of the test, K;

TS - - the air temperature at the standard state (273.15K), K;

V1 - - the free space volume of the test, L;

t - - the test duration, min.