ML20137S058
| ML20137S058 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/07/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20137S001 | List: |
| References | |
| NUDOCS 8602130566 | |
| Download: ML20137S058 (3) | |
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EVALUATION OF THE PUBLIC SERVICE COMPANY OF COLORAD0'S c
RESPONSE TO CONFIRMATORY ACTIONS 1, 4. 5, 10. AND 11 Item 1 This item was a request for an analysis of the capability of the Liner Cooling System (LCS), when fed by fire water, to prevent significant damage to any of
.the fission product barriers in the event of a high energy line break while the reactor is at 35% power.
The licensee complied with this request and submitted the results of the analysis of four limiting cases. Two of these cases assumed that the helium in the prestressed concrete reactor vessel (PCRV) was released (i.e., the PCRV was unpressurized) while the other two assumed it was not. Since the natural circulation of the helium in the PCRV provides a way to transfer heat from the reactor to the PCRV liner, which is cooled by the liner cooling system (LCS), the peak temperatures in the reactor are less for the pressurized case than for the unpressurized case. However, for the same reason the liner temperatures are higher for the pressurized case. The NRC contractor, the OakRidgeNationalLaboratory(0RNL),duplicatedthecalculationofthesefour cases with its ORECA computer program. The peak fuel temperatures, which determine the failure of the fuel particle coatings, calculated by ORNL are about 200*F less than those calculated by the licensee. ORNL's calculated maximum liner temperatures are somewhat higher than the licensee's, but not enough higher to cause liner failure. Thus, we conclude that for the depresurized morte of cooling, which is the preferred mode, the licensee can operate the LCS with fire water to prevent significant damage to any of the fission product barriers.
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' Item 4
.This item was a request for a determination of the time the licensee has before it has to start to depressurize the PCRV when cooling down from 35% power.
The licensee found this time to be 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and ORNL found that 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is quite conservative. Therefore, we conclude that the licensee should have ample time to depressurize the PCRV.
Item 5 This item was a request for an estimate of the maximum reactor power level at which it would be safe to perform a pressurized PCRV liner cooldown while protecting the integrity of the PCRV liner and the LCS.
The licensee found this power level to be 50% and ORNL found it to be greater than 50%. Therefore, we conclude that the 35% power limit is conservative.
Item 10 This item requested an evaluation of the effect of a PCRV limit cooldown from 35% power on the PCRV hot spots.
The licensee and ORNL both examined the PCRV hot spot temperatures that would be attained in this cooldown and found that the hot spot temperatures for this cooldown are well within the Ifmit stated in FSAR Section D.2.3.3, which is an approved limit. Therefore, we conclude that the cooldown is acceptable.
. Item 11 This item requested information on the impacts of re-establishing liner cooling after it has been shut off for a prolonged period of time.
One of the pressurized cases the licensee and ORNL analyzed for Item 1 corresponds almost exactly to the 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />,100% power, depressurized case described in FSAR Section D.2.3.2.
The results of these analyses show that the impacts of re-establishing liner cooling in the 35% power case are no worse than those for the depressurized sooldown after 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> from 100% power, which was previously i
evaluated in the Fort St. Vrain FSAR and found acceptable. Therefore, we conclude that re-establishing liner cooling in the 35% power case after it has been shutoff for a prolonged period of time is acceptable.
I Reviewer:
E. Lantz Note: ORNL Report is Enclosure 7 1
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