ML17221A487
| ML17221A487 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 10/28/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17221A486 | List: |
| References | |
| NUDOCS 8711050254 | |
| Download: ML17221A487 (4) | |
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CHAIRMAN UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON,"D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATFD TO AMENOMFNT NOS.
87 AND 26 TO FACILITY OPERATING LICFNSE NOS.
AND NPF-l6 FLORIDA POWER 5 LIGHT COMPANY, ET AL.
ST.
LUCIF. PLANT, UNIT NOS.
1 AND 2 DOCKET NOS. 50-335 AND 50-389 INTRODUCTION By application dated August 17, 198?, the Florida Power 8 Light Company {the licensee),
'requested a change to the Technical Specifications
{TS) for the St. Lucie Plant, Unit Nos.
1 and 2.
The proposed change would increase from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days the time period within which a scram test must be performed prior to reducing the shutdown margin below specified limits (TS 4.10. l.?>.
This surveillance requirement is part of the special test exception on shutdown margin
{TS 3/4. 10. 1).
The special test exception on shutdown margin is in effect during mode 2 for each unit and no more than six consecutive hours during mode 3 for Unit 2 only.
EVALUATION The special test exception on shutdown margin provides that a minimum amount of Control Element Assembly (CEA) worth is immediately available for reactivity control when CEA worth measurement tests are performed.
The minimum amount of worth is that reactivity equivalent to the highest estimated CEA worth.
The CEA worth measurement tests are part of the low power physics testing proqram that is followed after a refueling outage.
The objective o< the physics test-ing program is to measure various physics related parameters and ensure that they compare favorably to calculated values.
The. licensee must trip ffully insert) each CEA that is not fullv inserted from at least the 50K withdrawn position prior to reducing the shutdown margin to less than the limits of'pecification 3.1. 1. 1.
The present specification requires the trip test within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of reducing the shutdown margin.
In this way, the licensee is assured that all the CEA's that are not <ully inse'rted can trip while the shutdown margin is suspended.
Another technical-specification requirement also requires tripping -the CEA's, but for a different purpose.
The tripping of CEA's in this case deals with CEA drop time.
The CEA drop times must be calculated before initial reactor criticality following each refueling outage.
The drop* time tests before ini-tial criticality are usually performed more than one day (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) before the CEA worth measurements are made.
Thus, in practice, the CEA's are tripped at 8711050254 8
least twice following a refueling outage:
once for the drop time measurements and once previous to the period of time that the shutdown margin limit is suspended.
The licensee determined that there would be a slight increase in the proba-bility of a stuck CEA occurring between the time when the CEA's are tripped for the drop time tests and the time that the CEA's are tripped before suspen-ding the shutdown maqgin limit.
The licensee determined the increased proba-
'ility to be 1.3x10 based upon site operating data.
The licensee stated that the increased probability will have an insignificant impact to the combined probability of a positive reactivity insertion event occurring and a
CEA not inserting due to the change in the surveillance requirements.
The staff agrees that there is a small increase in probability that a stuck CEA may occur by changing the trip time from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to seven days.
The licensee also analyzed a number of postulated events that could occur during this period of time as part of the safety analysis.
The events are uncontrolled CEA withdrawal, inadvertent boron dilution, CEA ejection, and cooldown events.
The cooldown events are further divided into main steam line
- break, main feedwater line break, main steam safeiy valve spuriously opening, and inadvertent opening of an atmosphere dump valve.
The staff notes that these events can be postulated to occur not only during the time period between the CEA drop time measurements and the time that the shutdown margin limit requirement is suspended, but also during the period of time that the shutdown margin limit is suspended.
The licensee concluded that as a result o< any one of the postulated
- events, then would be no significant changes in the results and consequences of that postulated event.
The staff agrees that the results and consequences of any particular event are not significantly altered as a
result of the licensee's proposed change.
The staff also evaluated whether there could be any core geometry changes be-tween the time that the CEAs are tripped for drop time measurement and the time the shutdown margin limit requirement would be suspended.
The period of time considered is up to seven days.,
Our evaluation concludes that there are no.significant core geometry changes during this period of time.
The reactor vessel head is bolted to the reactor pressure vessel during this period of time.
- Thus, a11 components within the reactor pressure vessel are fixed in place.
The reactor protection system is operable and any scram signal would trip the withdrawn CEAs. If any problem occurs with an individual CEA, such as a
CEA drive mechanism, current TS requires the drop time to be measured again for that particular CEA to ensure that the CEA will trip and insert within the required drop time.
Thus the staff believes that this is adeauate
, assurance that the CEA's would be trippable during the seven day period prior to suspending the shutdown margin limit.
Based upon the above described analyses by the licensee and the independent evaluation of the staff, the staff finds that the proposed change is accep-table.
. ~ 'V ENYIRONMENTAL CONS IDERATION These amendments involve a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or a change in a surveillance requirement.
The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of'ny effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previous1y published a proposed fin'ding that these amendments involve no significant hazards consideration and there has been no public comment on such finding.
Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in lA CPP.
51.22<el<9).
Pursuant to 10 CFR 51.>~,
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments..
CONCLUSION We have concluded, based on the considerations discussed above, that (I) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, and (2l such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date:
October 28I '1987 Princi al Contributor:
E. Tourigny