ML19309C386
| ML19309C386 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 03/31/1980 |
| From: | Gallagher J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004080538 | |
| Download: ML19309C386 (2) | |
Text
D PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 JostPH w. oALLAGHEft as acinec e o"Odo'=" ce e n ews.,,
12153848 5003 March 31, 1980 f
)
Mr. Thomas A.
Ippolito, Chief Operating Reactors Branch 13 Division of Operating Reactors United States Nuclear Regulatory Commission 1
Washington, DC 20555 Dear Mr.
Ippolito:
This is our complete response to your letter o f January 10, 1930, to E.
G.
Bauer, Jr. which requested a tabulation for the years of 197d and 1979 of instances of control rods failing to fully insert on scram and a summary of other control rod drive malfunctions.
During 1978 and 1979, Peach Bottom Unit 2 experienced 3 scrams.
All control rods inserted to tne "00" position during each scram with the exception of control rod #42-39 which inserted to "02" on one occasion.
In this case, tne control rod was inserted to the "00" position by manual insertion.
Subsequent to this incident, there have been 4 reactor scrams with control rod #42-39 successfully inserting to rod position "00".
Control rod drive unit 942-39 is scheduled to be removed for inspection and maintenance during the Peach Bottom 2 refueling outage now in progress.
Also, with regard to other control rod drive malfunctions on Peach Bottom 2, an apparent uncoupling of the control rod and control rod drive was experienced during the performance of surveillance test ST 9.2 (Control Rod E x e r c i s e )'.
During tnis test (performed weekly), control rod #26-27 was successfully notched in to rod position "46" from the full
'out' rod position "48".
Upon withdrawal of the control rod, the ' rod overtravel' alarm (indicative that the control rod has uncoupled from the control rod drive) was received.
The control rod was re-inserted to rod position "46".
Subsequent rod withdrawals for engineering test purposes demonstrated tnat the control rod had re-coupled jfobl 5
IfD 80040805156
D Thouas A.
Ippolito, Cnief Page 2 successful!y.
Uncoupling could not be repeated and from 9-13-79 (date of uncoupling incident) to date has not been observed to occur during subsequent control rod exercise surveillance tests.
The associated control rod drive unit is scneduled for inspection and, if required, maintenance during tne Peach Bottom 2 outage now in progress.
During 1978 and 1979, Peach Bottom Unit 3 experienced 15 scrams.
In all 15 scram events, all of tne control rods successfully inserted to rod position "00" With regard to otner cont rol rod drive malfunctions on Peacn sottom 3, control rod
- 10-11 ' stuck' in at rod position "00" for 3 months prior to tne Peach Bottom 3 Reload 3 refueling outage.
During the Peacn Bottom 3 Reload 3 refueling outage, the control rod drive unit was removed for inspection and maintenance.
A small unidentified metal cnip was found wedged in the CRD ball cneck valve, tnereby preventing proper seating of tne check valve.
In effect tnis permitted the CRD drive flow to vent directly to the reactor vessel thereby preventing the first of two actions n e ce s s a ry for successful rod witndrawal.
Tais control rod drive unit nas been demonstrated to perform satisfactorily during the current Peach Bottom 3 operating cycle.
Should you nave any questions or require additional information, please do not hesitate to contact us.
Very truly yours, l