ML20211C853
| ML20211C853 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/09/1986 |
| From: | ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20211C806 | List: |
| References | |
| NUDOCS 8606120408 | |
| Download: ML20211C853 (4) | |
Text
d 3/4.10 SPECIAL TEST EXCEPTIONS SHUTDOWN MARGIN LIMITING CONDITION FOR OPERATION 3.10.1 The SHUTDOWN MARGIN requirement of Specification 3.1.1.1 may be suspended for measurement of CEA worth and shutdown margin provided reactivity equivalent to at least the highest estimated CEA worth is available for trip insertion from OPERABLE CEA(s).
APPLICABILITY:
MODE 2.
ACTION:
a.
With any full length CEA not fully inserted and with less than the above reactivity equivalent available for trip insertion, immediately initiate and continue boration at 2 40 gpm of 1731 ppm boric acid solution or its equivalent until the SHUTDOWN MARGIN required by Specification 3.1.1.1 is restored.
b.
With all full length CEAs inserted and the reactor subcritical by less than the above reactivity equivalent, immediately initiate and continue boration at B 40 gpm of 1731 ppm boric acid solution or its equivalent until the SHUTDOWN MARGIN required by Specification 3.1.1.1 is restored.
SURVEILLANCE REQUIREMENTS
-n 4.10.1.1 The position of each full length CEA required either partially or fully withdrawn shall be determined at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
4.10.1.2 Each CEA not fully inserted shall be demonstrated capable of full insertion when tripped from at least the 50% withdrawn position within 7 days prior to reducing the SHUTDOWN MARGIN to less than the l
limits of Specification 3.1.1.1.
ARKANSAS - UNIT 2 3/4 10-1 Amendment No.
I B606120408 860609 PDR ADOCK 05000368 P
1 DESCRIPTION OF AMENDMENT REQUEST The proposed change would revise the Surveillance Requirement 4.10.1.2 associated with Technical Specification 3.10.1, "Special Test Exceptions -
Shutdown Margin." This Technical Specification allows for suspension of the shutdown margin requirements of Specification 3.1.1.1 and provides that a minimum amount of CEA worth is immediately available for reactivity control when tests are performed for measurement of CEA worth and shutdown margin.
The existing Surveillance Requirement 4.10.1.2 requires that each control element assembly (CEA) not fully inserted shall be demonstrated capable of full insertion when tripped from at least the 50% withdrawn position within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to reducing the shutdown margin to less than the limits of Specification 3.1.1.1.
The proposed change will allow this surveillance to be performed within the past seven days instead of within the past 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
This will eliminate the requirement to perform a reactor trip during low power physics testing.
CEA drop time is measured per Surveillance Requirement 4.1.3.4 after replacement of the reactor vessel head following refueling, but CEA worths are measured during low power physics testing a few days later.
The proposed change will therefore allow for greater operational flexibility during low power physics testing by allowing a reasonable extension of the time period since demonstration of CEA insertion capability.
Extending the surveillance time period is justified since the extension does not significantly increase the probability of a stuck CEA.
The geometry of the components involved (fuel assembly, CEA, extension shaft, control element drive mechanism, upper guide structure) will not significantly change over the 7 day time period prior to reducing shutdown margin for measurement of CEA worth.
Because the CEAs insert as a result of gravitational force after removal of power to the drive mechanism holding coils, the probability of a stuck CEA due to an electrical malfunction will not significantly increase during the 7 days.
Surveillance Requirement 4.1.3.4 requires measurement of CEA drop time following removal of the reactor vessel head, or any maintenance on or modification to the CEA drive system which could affect the drop time.
Therefore, it is concluded that the proposed change will not significantly increase the probability of a stuck CEA.
The revised Surveillance Requirement will continue to provide assurance that the CEAs are trippable during low power physics testing.
i l
j
2r BASIS FOR PROPOSED NO SIGNIFICANT HAZARDS CONSIDERATION The proposed change does not involve a significant hazards consideration because operation of Arkansas Nuclear One - Unit 2 in accordance with this change would not:
(1) involve a significant increase in the probability or consequences of an accident previously evaluated.
The proposed change will extend 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 surveillance time period for a special test exception which allows measurement of CEA worth.
This extension will eliminate the requirement to perform a reactor trip during low power physics testing.
Calculation of shutdown margin excludes the contribution of the highest reactivity worth CEA which is assumed to remain fully withdrawn during the event.
Since shutdown margin must be reduced during measurement of CEA worths, Surveillance Requirement 4.10.1.2 provides added assurance that the maximum amount of negative reactivity is available for insertion should a reactor trip occur.
The geometry of the components involved (fuel assembly, CEA, extension shaft, control element drive mechanism, upper guide structure) will not change over the 7 day time period. Additionally, extending the surveillance time period to 7 days will not cause a significant increase in the probability of a stuck CEA due to an electrical malfunction since the CEAs insert as a result of gravitational force after a removal of power.
Therefore, the proposed change does not significantly increase the probability of previously evaluated accidents.
(2) create the possibility of a new or different kind of accident from any previously analyzed.
Existing FSAR analyses already assume a hypothetical stuck CEA.
Because the proposed change does not result in any changes to the facility as described in the FSAR, the possibility of a new or different kind of accident is not created.
(3) involve a significant reduction in a margin of safety.
The affected Specification 3/4.10.1 provides that a minimum amount of CEA worth is immediately available for reactivity control when tests are performed for CEA worth measurement.
The proposed change will not reduce the minimum amount of reactivity available during CEA worth measurement, and will, therefore, preserve the existing margin of safety.
o The Commission has provided guidance concerning the application of the standards for determining whether a significant hazards consideration exists by providing certain examples (48 FR 14870) of amendments that are considered not likely to involve significant hazards considerations.
Example (vi) relates to a change which either may result in some increase to the probability or consequences of a previously analyzed accident or may reduce in some way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan (SRP):
for example, a change resulting from the application of a small refinement of a previously used calculational model or design method.
In this case, SRP Section 14.2, " Initial Test Program" and SRP Sections 15.1.1, 15.1.2, 15.1.3, 15.1.4 and 15.1.5 which relate to Reactor Coolant System (RCS) overcooling events provide the pertinent acceptance criteria.
SRP Section 14.2 refers to Regulatory Guide 1.68, " Initial Test Programs for Water Cooled Nuclear Power Plants."
R.G. 1.68 outlines the elements of an acceptrble startup test program including requirements for CEA worth measurements during low power physics testing. The proposed change will facilitate CEA worth measurements without requiring a reactor trip and is consistent with R.G. 1.68 and SRP Section 14.2.
The proposed change does not affect the consequences of any events evaluated in accordance with SRP Section 15.1.1 through 15.1.5.
Since shutdown margin is reduced during CEA worth measurements, T.S. 4.10.1.2 provides added assurance that all CEAs are trippable.
By increasing the period during which shutdown margin may be reduced following performance of Surveillance Requirement 4.10.1.2, the proposed change may result in an insignificant reduction in the assurance provided.
The resultant increase in the probability of a stuck CEA is insignificant.
The proposed change has no effect on the consequences of any analyzed events since it does not affect the amount by which shutdown margin may be reduced.
Because the consequences of these events are not increased, the SRP acceptance criteria continue to be satisfied.
The proposed change satisfies the SRP acceptance criteria and therefore is most similar to Example (vi).
Therefore, based upon the discussion and reasoning presented above, AP&L has determined that this Technical Specifications amendment package does not involve a significant hazards consideration.
i
_. _ _