ML19317G787
| ML19317G787 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/16/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19317G777 | List: |
| References | |
| TAC-08884, TAC-8884, NUDOCS 8004010614 | |
| Download: ML19317G787 (3) | |
Text
.---.
m
/
S UNITED STATES
-' 4 NUCl. EAR REGUI.ATORY COMMISSION i
j h
WASHINGTON. D. C. 20686 e
- y
@v/
+....
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AENOMENT NO. 22 TO FACILITY OPERATTNG LICENSE NO. OPR-54 SACRAMENTO MUNICIPAL UTILITY DISTRICT RANCHO SECO NUCLEAR GENERATING STATION DOCKET NO. 50-312 Intm duction By letter dated August 2,1978, as revised by letter dated August 11, 1978, Sacramento Municipal Utility District (the licensee) requested revisions to the Rancho Seco Nuclear Generating Station (the facility) Technical Specifications (TS) which would incorporate changes to the Rancho Seco pressurization, heatup and cooldown limitations (pressure-temperature operating limit curves) and to the reactor vessel material surveillance program.
i Discussion The existing Rancho Seco TS curves #or heatup and cooldown are applicable for 1.8 x 106 thennal megawatt-days (1.8 effective full power years).
The proposed change would extend this time to five effective full power years (EFPY1 Evaluation The licensee has proposed reactor coolant system (RCS) pressure-tempera-ture operating limits to be applicable through five EFPY of operation.
The calculated maximun fluence at a point in the vessel wall equal to one-fourth of the wall thickness frggi tne,jnner surface at the end of five EFPY was stated to be 2.4 x 10lo n/cm'. However, dep
. specific location,thi's fluence could be as low as 1.8 x_]Ogding on the
,n/cm2 s There are four different weld materials in the reactor vessel beltline region.
'~
These are designated WF-29, WF-70, WF-154 and WF-233.. Based on chemical composition and weld location, WF-70.is expected to be the most limiting material. The licensee's submittal of August 11, 1978, included revisions to reflect the possible use of atypical weld wire in weld WF-70. This atypical wire had a lower nickel content (0.1% vs typically 0.6%) and a higher silicon content (1% vs typically 0.5%) than the wire nonnally used.
The effect of this variation is to cause a higher initial reference temperature for the nil ductility transition (RT wasusedbythelicenseeinhisanalysisDT). This higher value of RTNDT N 010
~
-..... Weld material WF-70 centains approximately 0.42% copper and 0.017%
phosphorus, and its initial reference temperature (as amended by the licensee's submittal of August 11,1978) was 120*F.
Five capsules containing this material are being irradiated at various facilities:
two capsules each at Davis-Besse Unit No.1 and Crystal River Unit No. 3, and one capsule at a test reactor. The capsule being irradiated at the test reactor is scheduled for removal during 1978, and the other capsules are scheduled for removal in 1981, 1982 and 1989.
Should the results of these capsule irradiations so indicate, we will require appropriate modification of the pressure-temperature limits.
Based on the composition, initial RT and neutron fluence at the locations of the various beltline mabials, the licensee estimated, using the curves in Regulatory Guide 1.99, Revision 1, the adjusted RT at five EFPY for each of these materials. From these adjusted vaNsofRT the licensee then developed the proposed operating limit curves.DT,he most limiting material according to the licensee's N
T analysis was WF-70 which had an adjusted RTNOT of 260*F at the end of five EFPY at the one-fourth thickness location.
We have reviewed the licensee's submittal.
Based on our review we agree that WF-70 is the limiting material, and conclude that the licensee's calculation:. of the adjusted RT at the end of five EFPY, including the effect of the possible use obtypical weld wire in weld WF-70, is acceptable and that his calculations of the limits on temperahre and pressure confom to the requirements of 10 CFR 50, Appendix G.
We have made certain changes to the TS proposed by the licensee to eliminate possible ambiguity and require timely submission of future proposed changes to these limits. These have been discussed with and agreed to by the licensee.
No changes were proposed for Technical Specification 3.1.3, " Minimum Conditions for Criticality." This specification requires that the reactor coolant temperature be above 525*F prior to criticality except for low power physics tests. This specification meets the require-ments of paragraph 4.A.2.c of Appendix G,10 CFR Part 50 and is acceptable.
Confornance with Appendix G,10 CFR Part 50 in establishing safe operating limitations will ensure adequate safety margins during operation, testing, maintenance and postulated accident conditions and constitutes an acceptable basis for satisfying the requirements to NRC General Design Criterion 31, Appendix A,10 CFR Part 50.
w
-Fm
Because this proposed change is in conformance with Appendix G to 10 CFR 50 which is designed to maintain an adequate safety margin, we conclude that the proposed change, as revised, does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in safety margin. We therefore, further conclude that the proposed change, as revised, does not involve a significant hazards consider-ation.
Environmental Consideration We have detennined that the amendment does not authorize a change in effluent types or total amounts nor an in:re.ise in power level i
and will not result in any significant envi'onmental impact. Having made this determination, we have further cc,icluded that the amendment involves an action which is insignificant from the standpoint of i
environmental impact and, pursuant to 10 CFR 451.5(d)(4), that an environmental impact statement, or negative declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion l
We have concluded, based on the considerations discussed above, that:
j (1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Comission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: August 16, 1978,
l l
.