1CAN059202, Revises Commitments Re Surveillance Testing,Temp Monitoring & Operator Actions Following HPI Backflow Event in 1989 & Updates NRC on Current Actions Being Taken as Result of Event
| ML20097A313 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/29/1992 |
| From: | James Fisicaro ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1CAN059202, 1CAN59202, NUDOCS 9206020267 | |
| Download: ML20097A313 (6) | |
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Ent$rgy Opstations,inc.
wm.. mo Operatioris-am. - a wn un a<uom May 29, 1992 1CAN059202 U. S. Nuclear Regulatory Commission Document Control Desk Hall Station P1-137 Washington, DC 20555
Subject:
Arkansas Nuclear One - Unit 1 Docket No. 50-313 j
License No,' DPR-51 Commitments Made concerning the Unit 1 HP1 Backflow Event Gentlemen:
A review of previous commitments to the NRC is being conducted by the commitment Management System Historical Review Project. Certain commitments associated with the Unit One liigh Pressure. injection System have been identified which need to be revised due to system modifications completed after the commitment was made. These commitments concern surveillance testing, temperature monitoring, and.. operator actions. Tt:e purpose of-this letter is to revise these. commitments, made after the Unit 1 IIPI backflow event In 1989, and to update the NRC'on' current-actions being taken as a result of this event NoLaction is being requested from the NRC.
On January 20, 1989,' Arkansas Nuclear.One, Unit One experienced a transient during which reactor coolant was allowed to backflow through.
the liigh 'Prassure Injection (HPI) system due to a f ailed-open check valve
-and unbalanced Reactor Coolant Pump (RCP) operations (two on, twojoff).
The corrective actions which were taken in response'to this event were documented in letters to the NRC dated February 14. 1989 (1CAN028909),
February 24, 1989 (ICAN028914), March 9, 1989 (ICAN038905). April 27, 1989 (ICAN048913), and May 25,.1989 (LER 50-313/89.-004, ICAN058911).
The NRC issued-a safety evaluation of.these corrective. actions dated--
August:11,--1989 (ICNA088904).
Since that time, modifications to the HP1 system h' ave-been made which improve the system and supersede the necessity'for-certain tests, surveillances and: operator responses.- Specifically. temperaturec instrumentation has been installed land the injection. lines have been modified to remove-the crossover. lines, eliminating the 'only credible flow path-for reactor coolant.backleakage.
Therefore, the previous
.comraitments are no longer needed and are beirg rescinded or revised.
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U. S. NRC May 29, 1992 Page 1 Attached is a summary of those commitments which have been affected by the modifications to the HPI system and a descriptio1 of present requirements concerning surveillance testing, temperature monitoring, and response to abnormal temperatures. These changes were reviewed prior to implementation in accordance with AN0's 10 CFR 50.59 program and no unreviewed safety question was involved.
Should you have any questions, please contact me.
Very truly yours, l
w
. y James J. Fisicato
)
Director. Licensing JJF/RJK/mmg attachments cc Mr. Robert Martin U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 400 Arlington. TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One - ANO-1 & 2 Number 1. Nuclear Plant Road Russellville AR 72801 Mr. Thomas'_W. Alexion NRR Project Manager, Region IV/ANO-1 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockd11e Pike Rockville. Maryland 20852 Ms. Sheri Peterson
,RR Project Manager. Region IV/ANO-2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852
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l Attachment to:
ICAN059202 Page 1 The Unit one HP1 backflow event occurred after a reactor trip in which i
two reactor coolant pumps tripped and high pressure injection was briefly initiated.
The unbalanced RCP operations created a differential pressure across the HPI system, and reactor coolant flowed backward through a failed open check valve (HU-34B) and the crossover line from the
'B' HPI line to the 'C' HPI line back to the RCS (see Figure 1).
In response to this event, redundant check valves were installed or each HPI injection line.
Requirements were instituted for testing the check valves, monitoring HP1 line temperatures, and taking certain corrective actions if abnormal temperatures occurr (LER 50-313/89-004 reported this event.)
During refueling outage IR9 (October 1, 1990 to January 6, 1991) two design change packages were imp emented for the HPI system.
DCP 89-1012B removed the crossover lines and installed two. additional injection lines per HPI train (see Figure 2).
With the crossover lines removed, no credible flow path exists for reactor coolant through~the HP1 system.
(This DCP was installed to resolve a small break LOCA concern identified during analysis of the backflow event.
License amendment requert dated August 8, 1990 (ICAN089002), discusses the modification in detail.)
DCP 89-1018 installed temperature instrumentation (Ri?s) with a recorder and a control room annunciator alarm for the HPI lines.
(This DCP also addressed the thermal stratification concerns discussed in NRC Bulletin f
88-08.)
Previous commitments in 1989 correspondence (letters 1CAN028909, ICAN028914, and LER 50-313/89-004) discussed actions being taken-to monitor HPI line temperature'for indications of reactor coolantz backleakage. Local temperature indicators and temperature tape were placed on each HPI line and operators recorded readings once per shift.
Also, the startup and shutdown procedures were revised to require logging HPI line temperature whenever unbalanced RCP operation-occurred. With the crossover lines now removed, unbalanced RCP operation is inconsequential as there is no credible flow path for reacto: coolant-backleakage.
Also, HPI line' temperatures are now-recorded by a remote temperature recorder and the control room has an annunciator alarm on high temperature (200 F).
Therefore, the startup and shutdown procedures no-longer require logging HPI line temperatures, and the operations logs procedure requires recording temperature readings daily from the _ remote indicator, not once per shift from local indicators.
Letter ICAN028914 discussed actions to be taken if a high temperature occurred.
If one or more HPI lines exceeded 240 F. the operators were instructed to close the corresponding crossover valve, which would require declaring one HPI train:inoperabic and entering an LCO, For temperatures grester than 150 F, a. condition report would be' initiated.
Abnormal temperature difrucaces between HPI lines (15-20'F) were to be
, confirmed by hand-held rfsos4 t ers - and investigated. Currently, with 'the crossover lines removed. reactor coolant backflow is no longer credible, i
l Therefore, no actions are required based on temperature differences.
between HPI lines. At a temperature c2 200 F, operators receive an.
annunciator alarm..A condition report and.an engineering evaluation is required.
(The high alarm setpoint of 200 F is well above the normal operating temperature of the line to avoid spurious alarms but will detect a backflow of reactor coolant.) A note in thL operations procedure states that temperatures greater than 240 F may result in an inoperable line but this is determined by an engineering _ evaluation.
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i Attachment tot 1CAN059202 Page 2 Letters 1CAN028909, ICAN038905, and LER 50-313/89-004 discussed testing the redundant chocPs valves in the four HPI injection lines.
As described, the testing included individual leak rate testing during refue. ling outages, full flow testing during cold shutdown, and performing a gross leak rate test in which operators observe HPI line pressure for i
one minute and initiate a condition report if the pressure increases by i
200 psi. With the removal of the crossover lines and the subsequent climination of the only credible flow patn for reactor coolant backflow, individual leak rate testing of these check valves is no longer needed.
i Full flow test'
'd gross leak rate. testing are st ll be ng done.
Full i
i flow testing (
cold shutdown is performed in accordance with the ANO l
inservice test ogram.
The gross leak. ratt test is being performed quarterly in conjunction with tne quarterly stroke test of-the motor operated 4.njection valves.
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FIGURE 1 RCS BACKLEAKAGE INTO HPI SYSTEM m
PRESSURIZER REACTOR VESSEL STEAM STEAM GENERAlOR GENERATOR A
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FIGURE 2 t
JURRENT CONFIGt' ' ATION
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