ML17221A731
| ML17221A731 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 04/12/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17221A730 | List: |
| References | |
| NUDOCS 8804280137 | |
| Download: ML17221A731 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE 1
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FLORIDA POWER 5 LIGHT COMPANY ET AL ST.
LUCIE PLANT, UNIT NO.
2 DOCKET NO. 50-389 Branch Technical Position RSB 5-1 (BTP RSB 5-1), "Design Requirements of the Residual Heat Removal (RHR) System," requires that test programs for PWRs shall include tests with supporting analysis to (a) confirm that adequate mixing of borated water added prior to or during cooldown can be achieved under natural circulation conditions and permit estimation of the times required to achieve such mixing, and (b) confirm that the cooldown under natural circulation conditions can be achieved within the limits specified in the emergency operat-ing procedures.
In addition, the plant design is to be such that the reactor can be taken from normal operating conditions to cold shutdown using only safety-grade systems.
Comparison with performance of previously tested plants of similar design may be substituted for these tests.
In NUREG-0843, "Safety Evaluation Repor t Related to the Operation of St. Lucie Plant, Unit No. 2," compliance with BTP RSB 5-1 is discussed.
As noted in the Safety Evaluation Report (SER), the licensee was specifically asked to demonstrate that the plant could be brought to.he shut down cooling system (SDCS) initiation in less than 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> using onIy seismic Category I
equipment, assuming the most limiting single failure, and with only onsite or offsite power available.
The staff also requested a demonstration that the seismic Category I auxiliary feedwater system had sufficient inventory to cooldown to the point of initiation of the SDCS.
The licensee referenced the natural circulation and boron mixing tests to be conducted at San Onofre Units 2
and 3
(SONGS) as being applicable to St. Lucie 2.
In NUREG-0712, "Safety. Evaluation Report for San Onofre, Units 2 and 3," the staff required a natural circulation test at SONGS 2 to demonstrate compliance with BTP RSB 5-1.
SONGS 2 natural circulation cooldown testing was performed on July 27, 1983.
The shutdown cooling system testing for SONGS 3 was performed on September 16 and 17, 1985.
The staff was assisted by its contractor, Brookhaven National Laboratory (BNL) in evaluating the tests at SONGS.
BNL reviewed the natural circulation cooldown test and the remote initiation of shutdown cooling test which were performed at SONGS 2
8 3.
The results of that review were given in a Technical Evaluation Report (TER) which also included a
sensitivity study to approximate the behavior of similar plants.
The staff then reviewed the SONGS TER.
Our major conclusion was that SONGS 2
Im 3
demonstrated full comp1iance with the requirements of BTP RSB 5-1.
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By letter dated Harch 13, 1984, the licensee submitted a copy of the report CEN-259 which evaluated the SONGS natural circulation cooldown test.
The licensee further stated that the report provided an evaluation of the applica-bilityy of the cooldown results to St. Lucie 2.
The staff was assisted by its contractor, BNL, in the evaluation of St. Lucie 2
with regard to conforming to BTP RSB 5-1.
The applicability of the SONGS natural circulation cooldown test to St. Lucie 2 was assessed.
Differences between the two plants were identified.
h'here differences existed, BNL used the results of the SONGS sensitivity studies to approximate the behavior of St. Lucie 2.
The results of that review are given in the enclosed TER.
Based on that review, BNL concluded:
a)
That adequate natural circulation was established and the plant was capable of removing the decay heat by natural circulation using only safety-grade equipment.
b)
That adequate boron mixing could be achieved within the available time prior to cooldnwn by natural circulation within the main flow path of the RCS using only safety-grade equipment.
c)
That cooling of the upper head without the Control Element Drive Hechanism (CEDH) fans could take about 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
d)
That cooldown of the RCS to the SDCS initiation temperature could be accomplished while maintaining adequate subcooling during the natural circulation using only safety-grade equipment.
e)
That without the CEDM fans, a sufficient supply of safety-grade cooling water was available to support the plant cooldown.
f)
During a prolonged period of upper head cooling without pressurizer
- heaters, the pressurizer level would have to be maintained at 6OX or higher to prevent steam bubble formation.
g)
That the RCS could be depressurized to the SDCS initiation pressure.
However, without letdown or pressurizer
- heaters, pressure control could be difficult and a strategy to depressurize utilizing the pressurizer PORYs may have to be considered.
h)
Operation of the atmospheric dump valves (ADVs) would be available at all times from the control room since the ADVs are DC motor-operated valves capable of being powered from safety-grade vital busses.
The ADVs could also be operated via manual handwheels in the event operation from the control room is not possible.
i)
A sufficient supply of safety-grade cooling water is available'to last the prolonged upper head cooling period even if the CEDH fans were not availa-ble as long as the condensate storage tank water does not have to be shared with Unit 1.
The water required is 276,000 gallons and assumes St. Lucie 2 requires the same upper head cooling time as SONGS 2.
j)
The HRC requirement to demon.'rate that the SCDS can be remotely initiated from the control room has not been addressed at St. Lucie 2.
The staff has reviewed the findings of the St. Lucie 2 TER and adds the following comments:
With respect to item g),
we suggest that the licensee review the TER and con-sider the need to include the use of the pressurizer PORVs as a supplementary method of cooldown.
With regard to item i), the staff has previously identified, in St Lucie 2 SSER 3, the need for a larger supply of cooling water.
The use of makeup
- water, from two 500,000 gallon city water storage
- tanks, was found acceptable to the staff.
With respect to item j), we find that the remote demonstration is not required, since it was addressed and found acceptable in the original SER.
Other than the items discussed
- above, we are in agreement with the BNL conclusions.
We therefore conclude that St. Lucie 2 has demonstrated compliance with the requirements of BTP RSB 5-1.
Dated:
Princi al Contributor:
D. Katze