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Water Packer Nearly-Implicit Scheme

Water Packer Nearly-Implicit Scheme. Rich Riemke. 2010 RELAP5 International Users Seminar September 20-23, 2010 West Yellowstone, Montana . Introduction.

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Water Packer Nearly-Implicit Scheme

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  1. Water Packer Nearly-Implicit Scheme Rich Riemke 2010 RELAP5 International Users Seminar September 20-23, 2010 West Yellowstone, Montana

  2. Introduction • RELAP5-3D currently has a water packing mitigation scheme (water packer) for the semi-implicit scheme but does not have a water packing mitigation scheme for the nearly-implicit scheme. • Purpose of this task was to add a water packing mitigation scheme to the code for the nearly-implicit scheme, to carry out a full debug/verification, and to document this in a letter report and in the code manuals.

  3. Subtasks • Necessary coding changes were made to add water packer for nearly-implicit scheme. • Verification consisted of 2 vertical fill problems (original problem used for the semi-implicit scheme and modified problem that requests a time step that violates the material Courant limit), manometer problem, current installation problems (script), and developmental assessment problems (script). • Letter report was written, manuals were changed, and updates were submitted for inclusion in the code.

  4. Coding Changes • Subroutines VIMPLT, PIMPLT, and HYDRO were modified to add water packing mitigation scheme for nearly-implicit scheme. • Detection logic to determine if water packing occurs is in subroutines PACKER (semi-implicit) and PIMPLT (nearly-implicit). • Value of variable FACTOR is different between semi-implicit scheme and nearly-implicit scheme. • Variable FACTOR is used in liquid momentum equation for semi-implicit scheme; used in sum and difference momentum equations for nearly-implicit scheme.

  5. Coding Changes (continued) • The 0.01 m/s change used in semi-implicit scheme is not used in nearly-implicit scheme. • Cleaned up coding in subroutines PACKER,VIMPLT, and VFINL (coding alignment and consistent coding style).

  6. Verification • Original vertical fill problem (maximum requested time step 0.05 s). • Subcooled water injected from below into vertical pipe initially filled with superheated steam. • Input flags: level model off, vertical stratification on, wall friction on. • Plots points obtained every time step.

  7. Verification (continued) • Semi-implicit scheme, no water packer.

  8. Verification (continued) • Semi-implicit scheme, water packer (spike at 8.1 s did not appear in RELAP5-MOD2; under investigation).

  9. Verification (continued) • Nearly-implicit scheme, no water packer.

  10. Verification (continued) • Nearly-implicit scheme, water packer.

  11. Verification (continue) • Modified vertical fill problem (maximum requested time step 1.0 s, violates material Courant limit). • Subcooled water injected from below into vertical pipe initially filled with superheated steam. • Input flags: level model off, vertical stratification on, wall friction on. • Plots points obtained every time step.

  12. Verification (continue) • Nearly-implicit scheme, no water packer.

  13. Verification (continue) • Nearly-implicit scheme, water packer (spike at 2.8 s under investigation).

  14. Verification (continue) • Manometer problem. • Consists of 20 volume pipe – 10 volumes oriented vertically down, 10 volumes oriented vertically up. • Bottom 5 volumes on each side filled with water. • Initial velocity -1.0 m/s at each junction; symmetry calculation with 1.0 m/s at each junction. • Input flags: level model on, packer on, vertical stratification off, wall friction off; problem used in developmental assessment (DA). • Water packer does not come on (level model handles junction crossing); results same as version 2.9.2 DA.

  15. Verification (continue) • Current installation problems (script). • Installation problems that use nearly-implicit scheme are identical to those without code modifications. • This is to be expected since these problems are such that water packing should not occur.

  16. Verification (continue) • Developmental assessment (DA) problems (script). • All run successfully except for LOFT L2-5 nearly-implicit scheme, which fails with and without the update with a thermodynamic property failure at the minimum time step. • ‘Diffem’ script shows some differences in some nearly-implicit DA problems (LOFT L2-5, water over steam, ROSA-IV SB-CL-18, Semiscale NC 1, 2, 3, 10; these were expected).

  17. Summary • Purpose of this task was to add a water packing mitigation scheme to the code for the nearly-implicit scheme, to carry out a full debug/verification, and to document this in a letter report and in the code manuals; this was completed. • Original fill semi-implicit scheme spike at 8.1 s and modified fill nearly-implicit scheme spike at 2.8 s are under investigation.

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