ML20116D353
| ML20116D353 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/30/1992 |
| From: | Link B WISCONSIN ELECTRIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20116D358 | List: |
| References | |
| CON-NRC-92-121 VPNPD-92-336, NUDOCS 9211050331 | |
| Download: ML20116D353 (2) | |
Text
. _ _ _ _.-.__ __
e-d' Wisconsin l;
' Electnc.
POWER COMPAM r
231 W Mchest Po tw 2046 ma>>co. va Lnot -
giaj 221 nat VPHPD-92-336 NRC-92-121 Oct obor 30,-1992 m
Document control Desk U.S,.HUCLEAR REGULATORY-COMMISSION
-Mail Station P1-137 Washington, DC 20555-Gentlemen:
.QPCKETS 50-266 AND S0-301-e l:
TECHNICAL SPECIFICATION FiECTIoM 15.3.10 BASIS CHAlied ERINT BEACH NQCJsEAR PLANT, UNITS i AND 2 On January 20, 1992, Point Beach Nuclear Plant, Unit 1 experienced a turbine runback as a result of the actuation of rod bottom bistabira which generated a rod bottom signal.
This ronback caused the axial flux difference-(AFD) to be out of band for seventeen 1
l.
minutes by computer-indication, violating the fifteen-minute 3 Technical Specification limit.
Axial flux difference, however,,was only out:of band for fourteen minutes by control board indication.
This event is deccribed in Licensee: Event Report _92-001-00,
" Turbine Runback Caused by Improper Post-Maintenance Testing,"
dated February 18, 1992.
The discrepancy between the two available axial flux difference indications was< attributed to-the calculational techniques used by the_ plant' process computer.
When' calculating axial flux differ-ence, the computer. takes a one-minuto-average-of the axial flux k
difference for each channel.
This resultsiin a delay of approxi-mately two minutes between the time-the axial' flux difference i
actually changes and'the time the computerJindicates the change.
- This results in the-computer lagging.behind the control board-andications.: :In order to correct-this problem, a software change to the' calculation of axial flux difference was implemented in September-1992. -The calculation,:instead_of using a one-minute average of Nuclear Instrumentation-System _(NIS) readings and-updatingLthe display onco'per minuto, now uses current NIS. readings
.-and updates the' display.once every four seconds.
- Now that-the computer software nas been implemented, the associated Technical Specifications-Basis baction also iast be updated.- The e
basis of Technical: Specification Section'.15.3.10,-" Control Rod and Power Distributjon Limits;" discusses tho_ provisions for monitoring i
axialrflux:. difference. _This portion!of:the basis currently states Lthe{ follow 1gcLJ t:
/g
-9213050331.921030 v
+
-PDRc ADDCK 05000266'-
,f( [ {-.
' iP:
' P D Ft.
J wbsWhyWIIinm& km Onwatiw
_a ~ v --
v
[
W D; cur nt Control D: k October 30, 1992 Page*2
" Provisions for monitoring the AFD on an automatic basis are derived from the plant process computer through the AFD monitor alarm.
The computer determines the one minuto average of each of the operable excore detector outputs and provides an alarm message immediately if the AFD for at least 2 of 4 or 2 of ; operable excore channels are outside the AFD limits and ti thormal power is greater than 50 percent of Rated Power."
As currently written, the basis describos the provisions for the AFD alarm prior to the software change.
Thereforo, this section of the basis is being updated to state the following CProvisions for monitoring the AFD on an automatic basis are derived from the plant process computer tnrough the AFD monitor alarm.
The computer determinos the AFD for each of the operable excora channels and providos a computer alarm if the AFD for at least 2 of 4 or 2 of 3 oporable excore channolz are outside the AFD limits and reactor power is greater than 50 percent of Rated Power."
Prior-to the implementation of the basis change, a 10 CFh 50.59 scrooning and ovaluation vero performed.
It was determined that changing the description of the AFD alarm in the Technical Specifications basis to match the actual implementation does not alter the intent of the basis, it simply providos a description of how axial flux diffrarenco is monitored.
This revision to the basis will clso not change the operation of l'olnt Beach Nuc1 car Plant.
Thoroforo, this revision does not involve an unreviewed safety question.
This scrooning and ovaluation are documented in SER 92-070, dated September 20, 1992.
Additionally, thi; basis chango underwent review and approval by the Point Beach Mar.ager's Supervisory Staff prior to its implementation.
Please insert the enclosed copy of revised Technical Specification basis page in your copy of the Point Beach TecN.1 cal Specifications.
Please contact us if there arr. any questions.
Sinceroly,
)
?
Ja /r -
,7.
/
/
(ss; /
Bob Link Vice President Huclear Power FDP/39 Enclosure cct NRC Regional Administrator, Region III NRC Resident inspector L.
-ai,
'