ML20079Q120

Corrected Pages B 3/4.6-26a to Amends 114 & 111 to Licenses DPR-19 & DPR-25,respectively

ML20079Q120
Person / Time
Site:	Dresden
Issue date:	10/24/1991
From:	Office of Nuclear Reactor Regulation
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ML20079Q125	List: ML20079Q120
References
NUDOCS 9111150205
Download: ML20079Q120 (2)

Text

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DRESDEN 11 DPR-19 Amendment No. 114 which includes a 60'F conservatism required by the original ASME Code of construction.

i Curve A - Hydrotesting As indicated in Curve A of Figure 3.6.1 for system hydrotesting, the minimum metal temperature of the reactor vessel shell is 80'F for reactor pressures less than 312 psig.

This 80'F minimum boltup tem-perature is based on an RT f 20 F for the top head plate (most NDT limiting material) and i 60 F conservatism required by the original ASME Code of construction.

At reactor pressures greater than 312 psig the minimum vessel metal temperature is established as 110'F.

The 110'F minimum temperature is based on a closure flange region RT f 20 F and a 90'F conservatism NDT required by 10 CFR 50 Appendix G for pressure in excess of 20% of the preservice hydrostatic test pressure (1563 psig).

At ap3roximately 620 psig reactor pressure the effects of pressuriza-tion secome more limiting than the boltup stresses at the closure flange region, as shown by the non-linear portion of Curve A intersect-ing the vertical 110 F line. The non-linear portion of the curve is dependent on the non-beltline region (which is actually more limiting than the beltline region through a vessel exposure of 22 effective full power years), and based on an RT f 40*F.

NDT Curve B - Non-Nuclear Heatup/Cooldown Curve B of Figure 3.6.1 ap)1ies during heatups with non-nuclear heat (e.g., recirculation pump leat) and during cooldowns when the reactor is not critical (e.g., following a scram).

The curve provides the minimum reactor vessel metal temperatures based on the most limiting vessel stress (non-beltine stresses).

As indicated by the vertical 80 F line, the boltup stresses at the closure flange region are most limiting below approximately 80 psig.

Above appproximately 80 psig, 3ressurization and thermal stresses become more limiting than the )oltup stresses which is reflected by the non-linear portion of Curve B.

Thenon-llnearportionofthecurve is dependent on non-beltline region (which is actually more limiting than the beltline region throug1 a vessel exposure of 22 effective full power years), and based on an RT f 40'F.

NDT l

Curve C - Core Critical Operation Curve C, the core critical operation curve shown in Figure 3.6.1, is generated in accordance with 10 CFR 50 A)pendix G which requires core critical pressure-temaerature limits to >e 40*F above any Curve A or B limits.

Since Curve 3 is more limiting, Curve C is Curve B plus 40'F.

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DRESDEN III DPR-25 Amendment No. iii which includes a 60'F conservatism required by the original ASME Code of construction.

Curve A - Hydrotesting AsindicatedinCurveAofFigure3.6.1forsystemhydrotestingforthe minimum metal temperature of the reactor vessel shell is 100'F reactor pressures less than 312 psig.

This 1000F minimum boltup i

0 temperature is based on an RTNDT of 40 F for the electroslag welo immediately below the vessel flange and a 60*F conservatism required by the original ASME Code of construction At reactor pressures greater than 312 psig, the minimum vessel metal temperature is established as 130'F.

The 130'F minimum temperature is based on a closure flange region RTNDT of 40'F and a 90 F conservatism 0

required by 10 CFR 50 Appendix G for pressure in excer.s of 20% of the preservice hydrostatic test pressure (1563 psig).

At approximately 650 psig the effects of pressurization are more limiting than the boltup stresses at the closure flange region, hence a family of non-linear curves intersect the 130 F vertical line.

Belt-line as well as non-beltline curves have been provided to allow sepa-rate monitoring of the two regions.

Beltline curves as a function of vessel exposure for 12, 14 and 16 effective full power years (EFPY) 6re presented to allow the use of the appropriate curve up to 16 EFPY of operation, r

Curve B - Non Nuclear Heatup/Cooldown Curve B of Figure 3.6.1 ap)1ies during heatup with non-nuclear heat (e.g., recirculation pump leat) and during cooldowns when the reactor is not critical (e.g.

following a scram).

The curve provides the minimumreactorvesseimetaltemperaturesbasedonthemostlimiting vessel stress.

As indicated by the vertical 100 F line, the boltup stresses at the closure flange region are most limiting for reactor pressures below approximately 110 psig.

For reactor pressures greater than approxi-mately 110 psig, pressurization and tiermal stresses become more limiting than the boltup stresses, which is reflected by the non-linear portion of Curve B.

The non-linear portion of the curve is dependent on non-beltline and beltline regions, with the beltine region temperaturelimitshavingbeenadjustedtoaccountforvesselirradi-ation (up to a vessel exposure of 16 EFPY),

The non-beltline region is limiting between a) proximately 110 psig and 830 psig.

Above approxi-mately 830 psig, tie beltline region becomes limiting.

Curve C - Core Critical Operation Curve C, the core critical operation curve shown in Figure 3.6.1, is generated in accordance with 10 CFR 50 A)pendix G whicfi requires core critical pressure-temaerature limits to )e 406F above any Curve A or B limits.

Since Curve 3 is more limiting, Curve C is Curve B plus 40'F.

B 3/4.6-26a