ML15111A058

Licensee Handouts (2 of 2) for 4/22/2015 Public Meeting Possible Roverd Section on Fixed Filtration (TAC Nos. MF2400-MF2409)

ML15111A058
Person / Time
Site:	South Texas
Issue date:	04/15/2015
From:	Harrison A South Texas
To:	Plant Licensing Branch IV
Regner L
References
TAC MF2400, TAC MF2401, TAC MF2402, TAC MF2403, TAC MF2404, TAC MF2405, TAC MF2406, TAC MF2407, TAC MF2408, TAC MF2409
Download: ML15111A058 (4)

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STPNOC RoverD: Risk over Deterministic GSI-191 Assessment 116 pages 4.3.2 Results (4.1a) to (4.1c) were integrated in FIDOE using well-known ordinary differential equation solvers2 implemented in a Python application to obtain Mc (t) (See Listing 11.1). The application is designed to provide solutions for different initial conditions and boundary conditions supplied in simple text files. The application is fully described in Section 11.1 with code listing and input files.

The amount of fiber bypassed to the core is primarily dependent on the initial sump pool concentration, Cp (t = 0), the filtration efficiency, f (*), and the decay heat demand, Qc (t) which is a fixed function of time. The pool concentration is defined by the amount of LDFG arriving in the ECCS sump pool for each Dismall and the pool volume. The filtration efficiency may be based on data with uncertainty (Figure 4.4) or can be set to an arbitrary linear function with slope Uncertainty associated with the variables, Cp (t = 0) and f (*) is evaluated by looking at lower and upper bound values for the variables. The minimum amount of LDFG fines in all the risk-informed scenarios is approximately 192 lbm Table 10.1 (the amount tested).

Assuming the total amount of LDFG transported to the sump is double the amount of fines, an upper bound for fiber mass in the pool for risk-informed scenarios would be about 550 lbm (note that smalls dont fully transport to the strainer). A reasonable upper pool volume limit is approximately 550,000 gal and reasonable lower limit is approximately 300,000 gal.

Table 4.2: Core mass (grams total) accumulation for bounding cases of initial ECCS sump pool fiber concentration Cp (t = 0) and upper and lower bounds of filter efficiency.

Cp (t = 0) gm/GAL lower:f (Msk (t = 150 min.)) upper:f (Msk (t = 150 min.))

High (0.832) 441 247 Low (0.158) 400 241 Sensitivity studies for fixed penetration fraction Previous investigators have used, or are familiar with, a so-called fixed filtration constant to estimate core fiber loading (Andreychek and McNamee, 2014, for example) and (for ex-ample ACRS, 2015, discussions on pages 209 and 210). To relate results of a fixed filtration constant approach to a fit of the measured data to the accumulated mass (as explained in 2

lsoda from the class, scipy.integrate.ode, is implemented. From the scipy.integrate.ode documenta-tion: Real-valued Variable-coefficient Ordinary Differential Equation solver, with fixed-leading-coefficient implementation. It provides automatic method switching between implicit Adams method (for non-stiff problems) and a method based on backward differentiation formulas (BDF) (for stiff problems).

Wednesday 15th April, 2015, 08:55 19 corresponding: keeej@stpegs.com

STPNOC RoverD: Risk over Deterministic GSI-191 Assessment 116 pages Section 4.3.1) a version of FIDOE was created to investigate fixed fiber penetration values.

The updated version of FIDOE uses (4.1) for mass conservation but f () is a constant value set by the user in input. The updated version of FIDOE is provided in Section 11.3 along with input and output files.

Three levels of fixed filtration, 0.4, 0.5 0.6, an 0.7 were applied at three levels of total strainer flow (5063 gpm, 6750 gpm, and 8438 gpm), and three levels of starting pool fiber concentration (0.11 gm/gal, 0.17 gm/gal, and 0.39 gm/gal). Note that the minimum mea-sured filtration for STP ECCS strainers as shown in Figure 4.4 is roughly 0.65. Results of the fixed filtration study are summarized in Table 4.3. Although the accumulation under this assumption (fixed filtration) will clearly be more than for the measured behavior, the sensitivities help confirm that the accumulated fiber on the core with 192 lbm in the sump will be less than 15 gm/FA.

Table 4.3: Sensitivity study of core fiber loading, Mc (t = 400min), using fixed filtration at three initial pool concentration (Cp (0)) levels: Normal = 0.17 gm gal

, Low = 0.11 gm gal

, and High = 0.39 gm gal (full block design)

Normal Concentration Mc (gm/FA) at strainer flow of:

Filtration 6750 gpm 8438 gpm 5063 gpm 0.4 18.1 28.3 15.0 0.5 13.0 16.0 10.4 0.6 8.8 10.9 7.3 0.7 5.7 7.3 4.7 Low Concentration Mc (gm/FA) at strainer flow of:

Filtration 6750 gpm 8438 gpm 5063 gpm 0.4 13.5 16.8 11.4 0.5 9.8 11.9 7.8 0.6 6.7 8.3 5.4 0.7 4.4 6.03 3.6 High Concentration Mc (gm/FA) at strainer flow of:

Filtration 6750 gpm 8438 gpm 5063 gpm 0.4 25.9 31.6 20.7 0.5 17.6 22.8 14.0 0.6 11.9 15.5 9.8 0.7 7.8 10.4 6.5 Wednesday 15th April, 2015, 08:55 20 corresponding: keeej@stpegs.com

STPNOC RoverD: Risk over Deterministic GSI-191 Assessment 116 pages Figure 4.3: Flow network for the three STP ECCS and CSS trains showing the three places debris is caught: the pool, the strainer, and the core during a CLB scenario. Shown as well are the various flow splits that take place between the places debris is caught. The flow split is defined by the amount of flow demanded by the core to remove decay heat.

Wednesday 15th April, 2015, 08:55 21 corresponding: keeej@stpegs.com

STPNOC RoverD: Risk over Deterministic GSI-191 Assessment 116 pages Figure 4.4: Filtration efficiency fits as a function of mass compared to measured data for the STP ECCS strainer modules. Efficiency fits obtained for the upper, central, and lower limits of the measurements are compared to the measured data.

Figure 4.5: Comparison of bounding cases for core LDFG accumulation after start of ECCS recirculation.

The mass accumulation should be divided by 193 to obtain gm/FA.

Wednesday 15th April, 2015, 08:55 22 corresponding: keeej@stpegs.com