ML19294B952
| ML19294B952 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 02/13/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19294B940 | List: |
| References | |
| NUDOCS 8003060442 | |
| Download: ML19294B952 (3) | |
Text
.
t ** "' %
p
?.
UNITED STATES
[.7
[h NUCLEAR REGULATORY COMMISSION
- q. -
WASHING TON. D. C. 20%$
4 b'/
C "g
(h.... [. #
,f SAFETY EVALUATI0fl DY THE OFFICE OF fiUCLEAR REACTOR REGULATI0fl SUPPORTING AMEflDMErlT fl0. 56 TO LICEflSE fl0. DPR-49 IOWA ELECTRIC LIGHT Afl0 POWER C0f1 patly CEflTRAL IOWA POWER COOPERATIVE CORfl BELT POWER TONETATIVE---
DOCKET fl0. 50-331 DEflE ARfl01.0 EflERGY CEtlTER Introduction By letter dated May 21, 1976, as supplemented by letters dated October 12, 1977 and October 10, 1979, Iowa Electric Light and Power Company (the licensee) requested a change to the Technical Specifications (Appendix A) appended to Facility Operating License flo. DPR-49 for the Duane Arnold Energy Center (DAEC). The proposed amendment would change the Technical Specifications for the thennal and pressurization limitations on the reactor coolant system to confonn with the requirements of 10 CFR 50, Appendix G.
Discussion 10 CFR Part 50, Appendix G " Fracture Toughness Requirements," requires that pressure-temperature limits be established for reactor coolant system heat-up and cooldown operations, inservice leak and hydrostatic tests, and reactor core operation.
These limits are required to ensure that the stresses in the reactor vessel remain within acceptable limits.
They are intended to provide adequate margins of safety during any condition of normal operation, including anticipated operational occurrences.
The pressure-temperature limits depend upon the metallurgical properties of the reactor vessel materials.
The properties of materials in the vessel belt-line region vary over the lifetime of the vessel because of the effects of neutron irradiation. One principle effect of the neutron irradiation is that it causes the vessel material nil-ductility temperature (RTNOT) to increase with time.
The pressure-temperature operating limits must be modified per-todically to account for this radiation induced increase in RTNDT by increas-ing the temperature required for a given pressure. The operating limits for a particular operating period are based on the material properties at the end of the operating period.
By periodically revising the pressure-temperature limits to account for radiation damage, the stresses and stress intensities in the reactor vessel are maintained within acceptable limits.
10 CFR Part 50, Appendix G also requires that for nozzles, flanges and shell regions near discontinuities, operating limits provide the same margin of safety as specified in ASME Code,Section III, Appendix G.
8003060
_2_
The magnitude of the shift in RTriDT is proportional to the neutron fluence to which the materials are subjected.
The shif t in RTt1DT can be predicted from Regulatory Guide 1.99.
To check the validity of the predicted shif t in RTf1DT, a reactor vessel material surveillance program is required. Sur-veillance specimens are periodically removed from the vessel and tested.
The results of these tests are compared to the predicted shifts in RTNDT, and the pressure-temperature operating limits are revised accordingly.
Evaluation The revised operating limits are based on the calculation method contained in Appendix G to ASME Code,Section III and Appendix G,10 CFR 50.
The operating limits are proposed for operation to six effective full power years (EFPY).
The limiting material is the feedwater nozzle material having an initial RTNDT of 40 F.
This material is limiting because of the high stressses in the nozzle region. However, since this region is not subjected to radiation, RTflDT values will not increase with time. Therefore, at some period of time the beltline region materials will become limiting. The proposed change in the Technical Specifications also includes a requirement that material sur-veillance capsules be withdrawn from the reactor vessel at 1/4 and 3/4 of service life.
We have reviewed the proposed operating limits for DAEC and have performed independent calculations to verify compliance with Appendix G,10 CFR 50.
We agree that feedwater nozzle material is limiting during the operating period to six EFPY.
From our calculations we conclude that the proposed operating limits are acceptable for six EFPY and are in accordance with Appendix G for this period of time. Conformance with Appendix G to 10 CFR 50 in establishing safe operating limitations will ensure adequate safety margins during operation, testing, maintenance and postulated accident con-ditions and constitutes an acceptable basis for satisfying the requirements to NRC General Design Criterion 31, Appendix A, 10 72 50.
We also have reviewed the proposed material surveillance capsule withdrawal schedule. Because of the low fluences on the vessel wall, the three capsule schedule is acceptable (the third capsule being a standby capsule). We con-clude that the proposed schedule is acceptable and is in accordance with Appendix H, 10 CFR Part 50.
Environmental Considerations We have determined that this amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this deter-mination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR Section Sl.5(d)(4) that an environmental impact state-ment, negative declaration, or environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(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 con-ducted in compliance with the Cormiission'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:
February 13, 1980