Physico–statistical approach taking defects into account and using binomial distribution - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 116

∞

 

t t

 

 

− lt t

∑

∫ ∫

i

T = exp ( ) d dt ;

[4.67]

   

0 I

 

   

i = 1

0 0

- γ-percentile lifetime T γ from the equation:



T



g

t

∑

∫

i

g / 100 = exp  − lt t ( ) d  .

[4.68]

I

 

 

i = 1

0

The indicators of life-cycle for the series connection of elements are:
- the average resource till write-off (full)

∞

 

t I

 

 

∑

∫ ∫

i

T = exp − lt t ( ) d dt ;

 

 

[4.69]

P I

mean

 

 

 

i = 1

0 0

- γ-percentile resource till write-off (full)

T g

from the equation:



T



g

I

∑

∫

i

g / 100 = exp  − ltt ( ) d  .

[4.70]

II

 



i = 1



0

In analyzing the availability and suitability for repair it was assumed that
during reconditioning of any element other elements work. The indicator of
suitability for repair [71] for series connection of elements - the average
reconditioning time is equal

I

∑

 

TTT
=

=

i

(). lt

[4.71]

 

P 0 B l

mean mean

i 1

In this case, the availability factor K r (complex value) is defined as
follows

T

i

I

￿ ￿ ￿ ￿ ￿

K = Π

0

,

[4.72] r i i

TT +

i = 1

0 B

mean

Here T 0 is the mean time to failure of i i-th element of a composite unit;

T

mean

is the average (mean) recovery time of i i-th element of a composite unit.
Formulas [4.67], [4.68], [4.71], [4.72] take into reliability indicators
up to the first failure. The mean reliability indicators of the elements to
failure for the reconditioning process with increasing failure intensity are
determined using the formulas given in Ref. 71.

4.2.3 Criterion values of failure probability, based on the
procedure described in section 4.2.2

The reliability criteria are selected by comparing the reliability indices
obtained by creating a new design or when upgrading an old one, or when