ML19305A785
| ML19305A785 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/12/1980 |
| From: | Crouse R TOLEDO EDISON CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003180350 | |
| Download: ML19305A785 (10) | |
Text
'
TOLEDO
%mm EDISON R o.an P Cra.se Docket No. 50-346
..n.m License No. NPF-3
"*'* 25S422' Serial No. 596 March 12, 1980 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D.C.
20555 Attention:
Mr. Robert N. Reid, Chief Operating Reactors Branch No. 4 Division of Operating Reactors
Dear Mr. Reid:
On March 4, 1980 representatives from your organization, Florida Power Corporation, Babcock & Wilcox (B&W) and all operating licensees owning B&W nuclear steam supply systems met in your offices to discuss the Feb rua ry 26, 1980 transient at Crystal River Unit No. 3.
This letter responds to your staff's requests as later documented in your letter of March 6, 1980 for Davis-Besse Nuclear Power Station Unit No. 1.
The item numbers identified in the attachment are consistent with those in Enclosure 3 of your letter. We are available to discuss any ques-tions you may have on this response.
Very truly yours, n
M t
i RPC/TJM Attachment PP b/9 THE TCLECO EDISCN CCMPANY ECISCN PLAZA 300 MACISCN AVENUE TCLECO, CHIO 436*2 8003180351)
SUBMITTAL FOR THE DAVIS-BESSE NUCLEAR POWER STATION UNIT 1 FACILITY OPERATING LICENSE NPF-3 IN RESPONSE TO A 10 CFR 50.54(f)
REQUEST DATED MARCH 6, 1980 CONCERNING CRYSTAL RIVER LWIT NO. 3 TRANSIENT OF FEBRUARY 26, 1980 This response is filed in accordance with 10 CFR 50.54(f).
This letter provides information about the relationship of the Crystal River Unit No. 3 transient of February 26, 1980 to the Davis-Besse Nuclear Power Station, Unit 1.
By 4
Nuclear Services Director, Nuclear Services For R. P. Crouse Vice President, Nuclear Sworn to and subscribed before me the twelfth-day of March, 1980.
/L2 e/
Notary Public UT:CA L. CCITT L Notary Puti - itxa :t CNo My Comm4:s'on Spues Fec. 9.1982 8003180
Docket No. 50-346 Davis-Besse Nuclear Power Station License No.
NPF-3 Unit 1 Serial No. 596 Response *o NRC 10 CFR 50.54(f)
March 12,'1980 Request L.ncerning Crystal River - Unit No. 3 Attachment Transient of February 26, 1980 Question 1 Summarize power upset events on Non-nuclear Irstrumentation/ Integrated Control System (NNI/ICS) that have previously occurred at your plant.
Response
Since initial startup the Davis-Besse Nuclear Power Station Unit I has had one power supply failure which affected the NNI/ICS when the reactor was critical. This failure involved a bus which supplied power to the ICS/NNI. Refer to Davis-Besse Nulcear Power Station License Event Report No.79-009 for details. One failure of a source bus affecting the NNI and ICS systems was experienced when the reactor was shut dcwn.
This failure was due to maintenance activity on the inverter that supplied
.his bus.
Prior to initial startup of DB-1 there were failures of these buses when the inverters and the other systems were being tested.
Question 2 Specifically review the Crystal River event, address your susceptibility to it in general.
Response
Toledo Edison Company has reviewed the Crystal River event considering how the Davis-Besse design would have responded. To date our review indicates DB-1 could have responded in a similar manner for the first 3 minutes and 20 seconds. Throughout the entire event, however, a power supply failure in the NNI system at Davis-Besse would not have affected the following instruments:
a.
Hot leg narrow range temperatures b.
Hot leg wide range pressures c.
Pressurizer levels d.
Steam generator startup range levels e.
Steam geuerator pressures f.
High pressure injection flows g.
Low pressure injection flows The original DB-1 design removed these instruments from the NNI system and now supply these -from safety-grade redundant power supplies.
In addition, the only other key plant parameter-is cold leg wide range temperature. DB-1 has redundant indication of this on each loop that can be displayed on the station computer. One of these indicators is on the NNI-X power supply and the other indicator is on the NNI-Y power supply. 'The computer does not require any power from the NNI for its operation.
'Three minutes and 20 seconds after the NNI power failure (14:26:41) the high pressure injection (HPI) system was automatically started at Crystal River. The operators at Crystal River had to manually isolate the containment. -Manual isolation would not have been required at DB-1.
When the reactor coolant system pressure reduced to 1650 psi at Davis-Besse -(rather than 1500 psi at Crystal River) the HPI pumps would have been automatically started and the Davis-Besse Unit I containment would have been automatically isolated.
At 14:26:54 the reactor coolant pumps were manually tripped at Crystal River. At Davis-Besse they also would have been manually-tripped when the high pressure injection was automatically started due to low reactor coolant system pressure.
In addition, when the four reactor coolant pumps were tripped, the auxiliary feedwater pumps at Davis-Besse would have been automatically started by our steam and feedwater rupture control system (SFRCS). This system is a totally safety grade system that is used to initiate the auxiliary feedwater (AFW) system.
At 14:33:30 a high reactor coolant system pressure alarm occurted at Crystal River due to the system going water solid. The Davis-Besse design utilizes HPI pumps with a reduced pressure shut-off head below that of the high pressure alarm. The HPI system would have started, the operators would have followed the pressure increase on the reactor coolant system and they would have controlled the pressurizer level (whose indication is safety grade) with the HPI pumps after they had assured that they were properly subcooled. There would have been no release from the reactor coolant system into the containment vessel after the pressurizer block valve was closed.
At 14:38:15 they actuated the manual controls that close the control valve on their steam generator B to prevent overfilling. The Davis-Besse design has a essential safety grade steam generator level control system independent of NNI and ICS power. This would have controlled the level in each steam generator at 96 inches indicated following the safety features actuation system (SFAS) trip.
At 14:44:31 Crystal River received a 4 psig containment pressure trip due to -the flow of water from the water solid reactor coolant system into the containment through the open pressurizer safety valve. Davis-Besse would not have tripped on four psig containment pressure due to the fact the only water that would have gone into the containment would have been during the. initial period of time when the PORV was open prior to its isolation.
3 At 14:51:57 the rupture matrix associated on steam generator B "oped due to the fact they were putting a large volume of cold water into the steam generator in order to achieve a 95% operating range level. The Davis-Besse raised loop design requires only 96 inches indicated steam generator level during this condition. This level is controlled automat-ically by a safety grade level control system. As a result the system would not have _ cooled down as much as at Crystal River and DB-1 would not have had the same low pressure on the st:am generator secondary side.
At 14:52 Crystal River throttled their HPI in order to reduce the reactor coolant system pressure below 2300 psig in order to stop the flow through the pressurizer safety valve. At Davis-Besse we would have only had to throttle the HPI flow to control the pressurizer level.
It would not have been necessary to control the reactor coolant system pressure because the reduced shut-off head of the HPI pumps. The reactor system pressure would have stopped increasing at about 1700 lbs.
Pressurizer heaters would then have returned reactor coolant system pressure to no rmal.
Question 3 Set forth the information presented by each licensee in the meeting on March 4.
Response
The following additional information was presented during the NRC and B&W Owners meeting on March 4, 1980.
Toledo Edison has evaluated how Davis-Besse would respond to a similar transient. This is discussed in response to Question 2.
We have reviewed our control circuits for the PORV and the pressurizer spray valve and we find that they would have reacted similarly to those at Crystal River.
4 We have also determined that NNI power system failures can cause the ICS to act improperly. This could lead to a reactor trip.
NNI does not af fect the capability of the reactor to trip from the interim anticipatory reactor trip system (ARTS)
The interim ARTS system at Davis-Besse receives its signals from the same safety grade sensors that go into the SFRCS to detect the loss of feedwater. The turbine trip signals come directly out of the electro-hydraulic control system for the turbine generator which does not use signals from the NNI or the ICS. Additionally automatic containment isolation, HPI initiation and AFW initiation and control are not affected by an NNI power failure.
Question 4 Address information available to the operator following various NNI/ICS power upset events, include a discussion of:
a.
How the ' operator knows what information is reliable b.
What information is needed for cold shut down
4
-Response As indicated in the response to question 2, items a g are not affected by an NNI/ICS power supply. failure and reactor coolant wide range cold leg temperature is available on the computer as described above.
Details of functions lost to the operator are contained in " Davis-Besse Nuclear Power Station Unit No. 1 System Procedure 1105.06-NNI Operating Procedure". These parameters and controls of the safety related systems will insure proper reactor shutdown and maintenance in hot shutdown conditions.
To continue to take the plant to a normal cold shutdown conditions information and controls are required on the following systems:
1.
The makeup system 2.
Letdown system 3.
Chemical addition system 4.
Clean liquid radwaste system up to their receiver tanks 5.
Borated water storage tank 6.
Reactor coolant pumps 7.
Reactor coolant pressurizer spray system 8.
Pressurizer heaters Operating procedures and training will be provided for transition to cold shutdown as a result of Toledo Edison's expanded response to IE Bulletin 79-27.
Question 5
- Address the feasibility of performing a test to verify remaining informa-tion following various NNI/ICS power upsets.
Response
Such a test could only be performed when the unit is shutdown and after a detailed test procedure had been prepared. This test procedure could not be generated until the information needed in response to Question 7 has been completed. We are presently determining if such a test could be prepared and completed during our upcoming refueling outage without adversely affecting the schedule. This will be discussed by Toledo Edison following our revised response to IE Bulletin 79-27.
Question 6 Address each Crystal River proposed fix--applicable to your plant--and their proposed action.
Response
The following corrective actions have been proposed by Crystal River:
I.
CR-3 Corrective Actions Prior to Startup 1.
" Thorough testing of the NNI (X) system to determine the cause of the initial failure".
~
5 Since March 4, 1980 the preliminary determination of the cause of the failure was a misaligned voltage buffer card recently installed in the NNI cabinets for the reactor coolant saturation meter. This equipment has not yet been installed at DB-1.
For this modification the unit will be shutdown and revised installation instructions currently being developed by the manufacturer will be followed.
2.
" Modify PORV's so that a power failure will close the valve".
This modification is currently being scheduled for completion prior to the startup following the spring refueling outage.
3.
" Modify pressurizer spray valves so the NNI power failure will close valve".
This modification is currently being scheduled for completion prior to startup following the spring refueling outage.
4.
" Provide positive indication of all three relief valves on the pressurizer".
This modification is scheduled for installation within 30 days of its delivery or during the spring refueling outage.
5.
" Establish procedural controls of selective sources for indica-tien and control".
In conjunction with the expanded response to IE Bulletin 79-27 procedural controls will be in place prior to startup af ter the spring refueling outage.
6.
" Train all operators in response to NNI and ICS failures".
DB-1 operators are reviewing " System Procedure 1105.06-NNI Operating Procedure" in conjunction with the February 26, 1980 transient information. More detailed training will include results of IE Bulletin 79-27.
7.
" Move 120 volt AC ICS (X) power to Vital Bus".
Both X and Y power to the NNI and ICS systems are presently on unterruptible buses at Davis-Besse that are supplied by inverters and no change is required.
8.
" Repair the events recorder system".
The DB-1 system for event recording is working properly. No action is required.
6 9.
" Initiate a more extensive surveillance program on the events recorder system".
The DB-1 system for event recording is maintained on a regular basis. No action required.
10.
" Provide operators with redundant indications of main plant pa rame te rs".
Davis-Besse presently has redundant safety grade indicators for all main plant parameters except for the reactor coolant wide range cold leg temperatures. These are >rovided on the computer and no changes are currently planned.
II.
CR-3 Corrective Actions During the Next Refueling Outage a.
" Install indicating lights on all vital bus feeds".
Toledo Edison vill respond to this on or before March 17, 1980.
b.
" Modify vital bus panels for quick fuse replacement".
This is not applicable to Davis-Besse which utilize hinged cabinet doors for access.
c.
" Modify emergency feedpump auto start circuit and reactor trip circuits so that any power failures will not prevent activation on low steam generator level".
Davis-Besse has a safety grade auxiliary feedwater initia-ting system. No modification is required. The DB-1 interim ARTS is not fed out of the NNI or ICS system and therefore no modifications are needed.
III. Long Term Corrective Actions a.
" Investigating upgrading of the NNI system capabilities".
As a result of the failure modes and effects analysis performed on the ICS for NRC Bulletins and Orders Task Force, Toledo Edison has initiated a study on the ICS and NNI power supplies, both internal and external. The results will be available for Toledo Edison's response to IE Bulletin 79-27.
b.
" Provide a new remote shut down panel with redundant instruments and control capabilities".
Davis-Besse presently has a totally safety grade auxiliary shut down panel installed. No modifications are planned.
7 c.
"Make control grade loss of main feedpump ' trips safety grade".
Toledo Edison has committed to install a safety grade ARTS as a result of the NRC Bulletins and Orders Task Force efforts. This system is scheduled to be installed during the refueling outage in 1981. Currently, trip signals come from safety grade pressure switches.
d.
" Provide auto transfer scheme to backup inverter supplies for the ICS and the NNI".
DB-1 presently has static transfer switches on our inverters that supply these systems. No change is proposed.
e.
" Replace computer main _ frame with state of the art computer for alarms and data trending".
As a result of previous investigation, Toledo Edison has decided to undertake a program to replace the current station computer as well as provide additional data manipulation capabilities. A definitive schedule has not been developed for these changes.
f.
" Provide backup information system in the -technical support center".
This is a recommendation of Lessons Learned Task Force efforts. An information system will be available in the long-term upgraded Technical Support Center.
g.
" Investigate the installation of video tape and sound recording equipment for the main control board".
Toledo Edison will investigate this along with other informational aquisition systems. Any selected systems will be incorporated in the long-term upgraded Technical Support Center effort.
h.
" Investigate 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> coverage of instrument technicians and electricians".
Toledo Edison will investigate tha 70ssibility of providing extended coverage for instrument te:hnicians and electri-cians.
Question 7 Erpand your review under IE Bulletin 79-27.
Tell us your schedule for completion of the review of the expanded scope as discussed on March 4.
s F..
g
Response
~
An expanded response to IE Bulletin 79-27 for DB-1 will be submitted to
.the NRC-by April. 15, 1980. The revised scope in this study will include power supply failures in the' NNI and the ICS systems, as well as related bus-failures.. The bulletin response will address the power supply failures.to the systems required to go to cold shutdown.
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