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 dierential equation solvers2 implemented in a Python application to obtain Mc(t) (See Listing 11.1). The application is designed to provide solutions for dierent initial conditions and boundary conditions supplied in simple text "les. The application is fully described in Section 11.1 with code listing and input "les.

The amount of "ber bypassed to the core is primarily dependent on the initial sump pool concentration, Cp(t = 0), the "ltration eciency, f(*), and the decay heat demand, Qc(t) which is a "xed function of time. The pool concentration is de"ned by the amount of LDFG arriving in the ECCS sump pool for each Dsmall i

and the pool volume. The "ltration eciency 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 "nes 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 "nes, an upper bound for "ber 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 "ber concentration Cp(t = 0) and upper and lower bounds of "lter eciency.

Cp(t = 0) gm/GAL lower:f(Mk s (t = 150 min.))

upper:f(Mk s (t = 150 min.))

High (0.832) 441 247 Low (0.158) 400 241 Sensitivity studies for "xed penetration fraction Previous investigators have used, or are familiar with, a so-called "xed "ltration constant to estimate core "ber loading (Andreychek and McNamee, 2014, for example) and (for ex-ample ACRS, 2015, discussions on pages 209 and 210). To relate results of a "xed "ltration constant approach to a "t of the measured data to the accumulated mass (as explained in 2lsoda from the class, scipy.integrate.ode, is implemented. From the scipy.integrate.ode documenta-tion: Real-valued Variable-coecient Ordinary Dierential Equation solver, with "xed-leading-coecient implementation. It provides automatic method switching between implicit Adams method (for non-sti problems) and a method based on backward dierentiation formulas (BDF) (for stiproblems).

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 "xed "ber 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 "les.

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

Table 4.3: Sensitivity study of core "ber loading, Mc(t = 400min), using "xed "ltration 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 "ow 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 "ow 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 "ow 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 "ow splits that take place between the places debris is caught. The "ow split is de"ned by the amount of "ow 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 eciency "ts as a function of mass compared to measured data for the STP ECCS strainer modules. Eciency "ts 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