ML20108B668

Supplementary Info to Addendum 1 to, Addendum to Bart A1: Computer Code for Best Estimate Analysis of Reflood Transients

ML20108B668
Person / Time
Site:	Mcguire
Issue date:	02/26/1985
From:	WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML20108B660	List: ML20108B668 NRC-85-3011, Forwards Supplementary Info to WCAP-9561,Addendum 1, Addendum to Bart A1:Computer Code for Best Estimate Analysis of Reflood Transients. Timely Completion of Review Needed to Support Anticipated Mar 1985 Startup
References
TAC-56336, WCAP-9561-ERR-A, WCAP-9561-ERR-ADD-01, WCAP-9561-ERR-ADD-1, NUDOCS 8503070428
Download: ML20108B668 (11)

Text

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ATTACHMENT SUPPLEMENTARY INFORMATION l

TO WCAP-9561 ADDENDUM 1 8503070428 850226 PDR ADOCK 05000370 P PDR 8289Q:10/022185

1. PRESSURE During the reflood portion of the transient, the BART code assumes a constant pressure as shown in Figure 1. This pressure of 16 psia is below the lower limit of the approved pressure band which is 20 psia. Using a pressure outside the approved band makes it necessary to demonstrate that the BART calculations are still conservative.

In the FLECHT Skewed Test Series, tests 13404 and 13609 have identical conditions except for system pressure. The pressure in test 13404 was 40 psia and the pressure in test 13609 was 20 psia. The clad temperatures in the data and the BART calculations of the tests will be examined to show that lowering

. the pressure retains the conservatism in BART. Figure 2 shows the clad temperature trani.ients at the 6 foot, 8 foot, and 10 foot elevations for both the test data and the BART calculations. The peak clad temperatures are listed in the following table.

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Data Data BART BART Test 13609 Test 13404 Test 13609 Test 13404

' ' Elevation 20 psia 40 psia 20 psia 40 psia (feet) PCT (*F) PCT (*F) PCT (*F) PCT (*F) 6 1591 1569 1614 1608 8 1731 1788 1829 1882 10 1715 1851 2000 2088 In these tests, BART conservatively overpredicts the clad temperatures.

Figure 3 compares the BART predicted cladding temperatures to the measured

' cladding temperatures. This figure shows that reducing the pressure does not adversely affect the conservatism in BART. Thus, the consequences of using 16 psia instead of 20 psia are that the BART calculations would still be conservative.

8289Q:10/022185

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2. INITIAL PEAK ROD TEMPERATURE t

The initial Riak rod temperature concerns only the maximum of the average rod temperature at 80C. Typical initial temperatures of the cladding a.re shown in Figure 4. The magnitude of the peak average rod temperature may vary

! depending on the break being analyzed. However, these variations may only slightly exceed or fall below the approved range.

A number of tests and BART predictions of the tests will be used to demonstrate that BART is conservative over a wide range of initial peak temperature. The sets of experimental data included:

A. FLECHT-SEASET 161 Rod Tests: 30817 31203 31805 32235 32333 B. G-2 Tests: 538 561 C. FLECHT Cosine Power Tests: 4831 5132 5342 6638 7934 Comparisons between BART and the data will be made using the cladding temperature rise ratio, A.

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8289Q:10/022185 L

If this ratio is greater than 1, BART censervatively overpredicts the cladding temperature rise. Figure 5 plots this ratio as a function of initial temperature. The points on the figure can be correlated in the form of a straight line using a least squares fit. The resulting correlation is:

A = 1.323 - 0.0001348* T NTM The small coefficient of T indicates that the conservatism in BART is NTM not very sensitive to initial temperature. This correlation can be used to determine the upper limit of T f r which A is greater than 1. The INITIAL calculated upper limit of T is 2396*F. Thus, for initial INITIAL temperatures lower than 2396*F, BART conservatively overpredicts the cladding temperature rise.

8289Q:10/022185

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3. REFLOOD RATE BART has been approved for transients in which the core reflood rate varies between 0.6 in./sec and 1.5 in./sec. The core reflood rate for a s, ample UHI transient is compared to the approved band in Figure 6. This comp ~arison shows that using BART for UHI applications remains within the NRC limits on core reflood rates except f ~ r a spike where the reflood rate drops to 0.5 in./sec.

l Heat transfer coefficients in BART are calculated using the mass flow rate through the core. The core mass flow rate through the core is approximately proportional to the product of the flooding rate, liquid density, and mass ,

. entrainment. When the reflood rate spiked down to 0.5 in./sec the mass I entrainment fraction concurrently increased. The mass flow rate through the core remained essentially the same even though the flooding rate spiked down.

This can be seen in Figures 7 and 8. Thus, the calculated heat transfer coefficient would not be significantly affected by the downward spike in flooding rate.

8289Q:lD/022185

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