ML20070L774

Proposed Tech Spec 3.3-5 Re Neutron Fluence Values for Pressure/Temp Limits Up to 17 EFPYs & Min bolt-up Temp for Vessel Closure Head Stud Tensioning

ML20070L774
Person / Time
Site:	Oyster Creek
Issue date:	03/12/1991
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20070L773	List: ML20070L771 ML20070L774
References
NUDOCS 9103200236
Download: ML20070L774 (1)

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Transformation temperature. The minimum temperature for pressurization at any time in life has to account for the toughness properties in the most limiting regions of the reactor vessel, as well as the effects of i fast neutron embrittlement. l I

curves (a),(b) and (c) on Figure 3.3.1 are derived from an evaluation of- I the fracture toughness properties performed on the specimens contained in I Reactor Vessel Materials Surveillance program Capsule No. 2 (Reference )

14). The results of dosimeter wire analypeo (Reference 14) indicated )

that the neutron fluence (E>1.0 MeV) gtthegndof17effectivefull power years of operation is 1.25 x 10'0 n/cm at the 1/47 (T= vessel ,

wall thickness) location. This value was used in the calculation of the l adjusted reference nil-ductility temperature which, in turn, was used to generate the pressure-temperature curves (a),(b), and (e) on Figure 3.3.1 l (Reference 15). The 250*F maximum pressure test temperature provides ample margin against violation of the minimum required temperature.

Secondary containment is not jeopardized by a steam leak during preocure testing, and the Standby Gas Treatment system is adequate to prevent unfiltered release to the stack.

Stud tencioning is considered significant from the standpoint of brittle fracture only when the preload exceed approximately 1/3 of the final design value. No vessel or closure stud minimum temperature requirements are considered necesocry for preload values below 1/3 of the design preload with the vessel depressurized since preloads below 1/3 of the design preload result in vessel closure and average bolt strosees which are less than 20% of the yield strengths of the vessel and bolting materials. Extensive service experience with these materiale has confirmed that the probabilit3 si trittle fracture is extremely remote at these low stress levelo, irrespect!ve of the metal temperature.

The reactor vessel head flange had e vessel flange in combination with the double "O" ring type seal are designed to provide a leak tight seal when bolted together. When the vessel head is placed on the reactor vessel, only that portion of the head flange near the inside of the vessel rests on the veneel flange. As the head bolte are replaced and tensioned, the vessel head is flexed slightly to bring together the entire contact surface adjacent to the "O" rings of the head and vescel flange. The original Code requirement was that boltup be done at qualification temperatures (T3OL) plus 60*F. Current Code requirements state (Ref. 16) that for application of full bolt preload and reactor pressure up to 20% of hydrostatic test pressure, the RPV metal temperature must be at RT HDT or greater. The boltup temperature of 85'F was derived by determining the highest value of (T3OL + 60) and the highest value of RTNDT, and by choosing the more conservative value of the two. Calculated values of (T3OL + 60) and RT HDT of the RPV metal temperature were 85'F and 36*F, respectively (Ref. 15). Therefore, selecting the boltup temperature to be 65'F provides 49'F margin over the current Code requirement based on RT NDT' Detailed stress analyses (4) were mado on the raactor vessel for both steady state and transient conditions with respect to' material fatigue.

The results of these analyses are presented and compared to allowable stress limits in Reference (4). The specific conditions analyr.ed included 120 cycles of normal startup and shutdown with a heating and cooling rate of 100*F per hour applied continuously over a temperature range of 100*F to 546'F and for 10 cycles e,f emergency cooldown at a rate of 300*F per hour applied over the same range. Thermal stresses from this analysis combined with the primary load OYSTER CREEK 3.3-5 Amendment No: 15, 42, 120 9103200236 910312 PDR ADOCK 05000219 P ppg