ML19339A773
| ML19339A773 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/17/1980 |
| From: | Udall M HOUSE OF REP., INTERIOR & INSULAR AFFAIRS |
| To: | Ahearne J NRC COMMISSION (OCM) |
| Shared Package | |
| ML18025B173 | List: |
| References | |
| NUDOCS 8011050068 | |
| Download: ML19339A773 (1) | |
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The Honorable John Ahearne g
Chairman, Nuclear Regulatory Com:nission
" ' i-Washington, D. C.
20555
Dear Mr. Chairman:
I have not received a response to'my July 16 letter concerning the June 28 control rod system failure at Browns Fe'rry 3.
I am concerne,d that the response may have been delayed as a result of an inability to calculate consequences of control rod failures that might occur following transients at full power.
I would hope, therefore, that in its forthcoming consideration of the ATWS problem the Commission will. seek to determine whether the staff has in fact been able'to calculate ATWS consequences under the assumptions of a range of design basis transients and common mode control rod failures.
i Sincerely, MORRIS K. UDALL Chairman 8011050 Ci(=S.
6 e
REP 0F.T ON THE BROWNS FERRY 3 PARTIAL FAILURE TO SCRAM EVENT ON JUNE 28, 1980 by the OFFICE FOR Af:ALYSIS AND EVALUATION OF OPERATIONAL DATA July 30, 1980 f
DUPLICATE DOCUMENT Entire document previously entered into system under:
ANO h N b,
h Prepared by: Stuart Rebin, Lead George Lan i<
No. of pages:
NOTE: This report documents results of studies completed to date by the Office for Analysis and Evaluation of Opera-tional Data with regard to a particular operating event.
The findings and recommendaticns contained in this report are provided in support of other ongoing NRC activities concerning this event. Since the studies are ongoing, the report is not necessarily final, and the findings j
and recor=endations do not represent the position or requirements of the responsible program office of the Nuclear Regulatory Comission.
y,
SSINS No..
6820 Accession No..
8005050076 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT JULY 3, 1980 IE BULLETIN NO. 80-17 FAILURE OF 76 0F 185 CONTROL RODS TO FULLY INSERT DURING A SCRAM AT A BWR Description of Circumstances:
On June 28, 1980, 76 of the 185 control rods failed to fully insert during a routine shutdown at TVA's Browns Ferry Unit No. 3 located at Athens, Alabama.
The reactor was manually scrammed from about 30 percent power in accordance with routine shutdown procedures.
The shutdown was initiated to repair the feedwater system.
The 76 control rod' that failed to fully insert were all on the east side of the core.
Following scram discharge volume (SDV) high level bypass and a short drain period of the SDV, a second manual scram was initiated and all partially inserted rods were observed to drive inward, but 59 remained partially withdrawn.
A third manual scram was made, again following high level in the SDV and bypassing for another short drain of the SDV, with the result that 47 rods remained partially withdrawn.
Following a longer drain of the SDV, an automatic scram occurred that was initiated by a scram discharge volume tank high water level signal when the scram reset switch was placed in " Normal"; with this scram all remaining rods fully inserted.
The total time elapse from the initial scram to the time that all rods were inserted was approximately 15 minutes.
Core coolant flow, temperature and pressure remained normal for plant conditions.
The unit is now shutdown and additional testing indicates that a possible cause of the malfunction was the retention of a significant amount of water in the east bank sc'am discharge volume.
In view of these interim findings and pending results of ontinued investigation, the following actions are to be taken.
Actions To Be Taken By Licensees:
All General Electric Boiling Wz'.er Reactors with operating licenses which are operati at an this Bulletin shall perform the e that are presently shutdown shall DUPLICF"E DOCUMENT Bulletin, perform surveillance Entire document previously nificant amount of water in the Scram entered into system under:
d piping and that the SOV vent valves
{
g7k of obstruction.
No. of pages: _
ll
SSINS No.:
6820 Accession No.:
UNITED STATES 8006190027 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 18,1980 IE Bulletin No. 80-17 Supplement No. 1 FAILURE OF 76 0F 185 CONTROL RODS TO FULLY INSERT DURING A SCRAM AT A BWR Description of Circumstances:
Please refer to IE Bulletin 80-17, issued July 3,1980, for complete details of the initiating event.
Although we are essentially confident that the event was caused by water in the Scram Discharge Volume (SDV) system, we do not yet have a complete explanation as to why the water was present.
The best estimate is that some type of blockage existed in the vent and'or drainage system for the SDV, precluding adequate drainage.
To ensure that the SDV is empty, Browns Ferry (BF-3) has installed instrumentation t-
- ontinuously monitor the water level in the scram discharge volume.
Such instrumentation is beir.g considered by other plants.
Since issuance of IE Bulletin 80-17, additional information has been identified.
Specifically:
a)
At Browns Ferry a discrepancy was found between the "as-built" scram discharge system and the "as-designed" system.
An unused one-inch (1") instrument line was found uncapped on the four-inch (4) drain header on the west side (the side whose rods scrammed) scram discharge
..alume vent system of Unit No. 3.
It is believed that this line improved the venting, and therefore the drain time for that system.
b)
It has been determined that the vent systems on some scram discharge volumes interconnect with vent headers that are also common with and are connected to other systems.
The interconnected " vent' 3ystems may contain water drained or being drained from those other systems.
This water could potentially affect performance of the SDV.
- Also, both the vent and drain sy. ems for the scram discharge system may contain long lengths of rciatively small bore piping.
Designs specify errors in the "as-installed" rmance (for example, due to DUPLICATE DOCUMENT Entire docurrent previously he NRC Staff regarding potential entered into system under.
injection of boron into the BWR 1 System (SLCS) when this manual ANO h[
h ential delays could be caused by N o.
of pages:
SSINS No.:
6820 Accession No.:
UNITED STATES 8006190032 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT jp WASHINGTON, D.C. 20555 6-J
/
July 22, 1980 IE Bulletin No. 80-17 Supplement No. 2 FAILURES REVEALED BY TESTING SUBSEQUENT TO FAILURE OF CONTROL RODS TO INSERT DURING A SCRAM AT A BWR Description of Circumstances:
At about 3:35 a.m. on July 19, 1980, a manual scram test was initiated at Dresden Unit No. 3.
This test was initiated in accordance with the require-ments of IE Bulletin No. 80-17.
The scram itself was accomplished (i.e.,
control rods inserted).
Following the scram, the Scram Discharge Volume (SDV) was monitored by UT in accordance with Item #3 of IE Bulletin No. 80-17.
The UT check followed the normal draining of the SDV at a time when personnel conducting the test believed the SDV to be empty.
However, the UT check revealed the scram discharge west header bank to be 80% filled with water (i.e., apparentiv the drain was not successful).
Upon investigation, it appeared that the SDV vent system did not function due to a stuck ball check valve (i.e., a ball check valve functioning as a vacuum breaker).
This ball check valve is installed in a tee connection downstream of the vent valve in a one-inch vent header which terminates in the reactor building equipment drain tank (RBEDT).
The ball check valve provides a vent path to the reactor building atmosphere in the event the vent header does not.
The vent header itself provides a path to other interconnections and extends into the RBEDT under the surface of water normally contained there.
Additional information has also resulted from scram testing at other BWRs as follows:
1.
At Duane Arnold, the Scram Discharge Instrument Volume (SDIV) drain valve was found installed so that pressure in the SDIV tended to unseat the drain valve disk.
This resulted in leakage out of the SDIV during the scram.
This was corrected by reversing and reinstalling the valve.
The scram tests were performed on July 12 and 13 and the drain valve was corrected before return to awer operations on July 17, 1980.
2.
At the Millstone Unit 1, he scram tests were performed successfully on July 11 through 14.
The function of the 10-second delay on scram reset (per Item #2.(j) of IE Bulletin No. 80-17) was tested separately from the scram tests.
Review of the separate test results by plant personnel established that the scram reset delay feature was not functioning in the scram circuits due to a wiring error on the circuit boards.
This was corrected.
s
IE Bulletin No. 80-17 July 22, 1980 Supplement No. 2 Page 2 of 2 3.
At Browns Ferry Unit No. 1, a test scram involving two rods was performed on July 19, 1980.
The test showed normal response of level switches in the SDIV.
When proceeding to drain the SDIV, however, the SDV did not empty as required and expected.
A vacuum in the SDV apparently existed which kept the system from draining.
Subsequently, the vacut. was cleared by operator actions and the volume drained properly.
Tests are continuing toward determination of the cause and to measure the vacuum.
4.
At Nine Mile Point Unit No. 1, one rod failed to scram during the manual scram test on July 14, 1980.
This was due to a failure of the scram pilot valve for that rod.
In view of the above-described events, the following actions in addition to those specified in IE Bulletin No. 80-17, including Supplement No. 1, are to be taken by BWR licensees.
1.
Each BWR licensee with a SDV vent system that depends on any component other than the vent valve alone for proper venting must provide an alter-nate vent path continuously open to building atmosphere on the side of the vent valve ~ piping away from the SDV.
This alternate vent path must be positive in its function at all times (i.e., a vent must be effective regardless of component operability other than the vent valve).
Plants have made corrections by providing a vent through a standpipe open to building atmosphere.
This was done at Browns Ferry Unit No. 3 and is being done at Dresden Units 2 and 3.
It is noted that due consideration to radiological aspects should be included.
An alternate vent path must be provided within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> following the telephone notification on July 19, 1980 in order to continue or commence operations.
2.
Report in writing within 5 days of the date of this Bulletin Supplement the confirmation of your action in response to the above.
Reports shall be submitted to the Director of the appropriate ilRC Regional Office and a copy shall be forwarded to the NRC Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Washington, D.C. 20555.
More information on the details of the Dresden and Browns Ferry events and modifications can be obtained by contacting the Dresden and/or Browns Ferry operating supervision.
In addi %n, we understand that a General Electric 1
Company task force is available for consultation at (408)925-3188.
For all boiling water power reactor facilities with a construction permit, this Bulletin is for information only and no written response is required.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80.
Approval was given under a blanket clearance specifically for identified generic problems.
IE Bulletin No. 80-17 (Supplement No. 2)
Enclosure July 22, 1980 RECENTLY ISSUED IE BULLETINS Bulletin Subject Date Issued Issued To No.
Supplement 1 Failure of Control Rods 7/18/80 All BWR power reactor to 80-17 to Insert During a Scram facilities holding OLs at a BWR 80-17 Failure of Control Rods 7/3/80 All BWR power reactor to Insert During a Scram facilities holding OLs at a BWR 80-16 Potential Misapplication of 6/27/80 All Power Reactor Rosemount Inc., Models 1151 Facilities with an and 1152 Pressure Traasmitters OL or a CP with Either "A" or "D" Output Codes 80-15 Possible Loss Of Hatline 6/18/80 All nuclear facilities With Loss Of Of f-Site Power holding OLs 80-14 Degradation of Scram 6/12/80 All BWR's with an Discharge Volume Capability OL 80-13 Cracking In Core Spray 5/12/80 All BWR's with an Spargers OL 80-12 Decay Heat Removal System 5/9/80 Each PWR with an OL Operability 80-11 Masonry Wall Design 5/8/80 All power reactor facilities with an OL, except Trojan 80-10 Contamination of 5/6/80 All power reactor Nonradioactive System and facilities with an Resulting Potential for OL or CP Unmonitored, Uncontrolled Release to Environment 80-09 Hydramotor Actua.or 4/17/80 All power reactor Deficiencies operating facilities and holders of power reactor construction permits i
80-08 Examination of Containment 4/7/80 All power reactors.with Liner Penetration Welds a CP and/or OL no later tnan April 7, 1980
. ~.
SSINS:
6820 Accession No.:
8006190074 UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTIUN AND ENFORCEMENT WASHINGTON, D.C.
20555 August 22, 1980 IE Supplement 3 ta Bulletin No. 80-17:
FAILURE OF CONTROL RODS TO INSERT DURING A SCRAM AT A BWR NRC staff evaluation of a potential single failure mechanism of the control rod drive control air system has identified the need for licensee actions in addition to those requested by IEB 80-17 and Supplements 1 and 2.
The potential single failure was discussed in IE Information Notice 80-30, which was issued on August 19, 1980.
It involves gradual or partial loss of control air system pressure, which could cause partial opening of scram outlet valves without rod motion.
The resultant accumulated seal leakage could conceivably fill the scram discharge volume in a few minutes.
Since not all operating BWR's have instrumentation presently installed to continuously indicate water level in the scram discharge volume headers and to provide a control room alarm or scram function, the possibility exists for the scram discharge volume to fill to a level which could prevent reactor scram before automatic protective action or before the operators could be warned.
In view of the possible single failure mechanism described above, the following actions are requested in addition to those specified in IE Bulletin 80-17, Supplements 1 and 2:
1.
For those plants in which the scram discharge volume headers are connected to the instrument volume by a 2 inch pipe, within fite days of the date of this Bulletin, provide or verify that procedures are in effect to:
a.
Require an immediate manual scram on low control rod drive air pressure with a minimum 10 psi margin above the opening pressure of the scram outlet valves.
b.
Require an imediate manual scram in the event of:
(1) Multiple rod drift-in alarms, or (2) A marked change in the number of control rods with high temperature alarms.
Installation of water ievt' instrumentation in the scram discharge volume with level alarm and con $inuous level indication in the control room, in response to Item B.1 of IEB 80-17 Supplement No. 1, may provide a basis for relaxation of the time for initiating a manual scram.
IE Bulletin No. 80-17 August 22, 1980 Supplement No. 3 Page 2 of 2 2.
In addition, every BWR licensee is requested within five days of the date of this bulletin to provide and implement procedures which require a functional test using water for the instrument volume level alarm, red block and scram switches after each scram event, before returning to power.
This procedure should remain in effect until modifications in addition to Item B.1 of IEB 80-17 supplement No. 1 are completed to substantially increase reliability of water level indication in the scram discharge volume (s).
Licensees of all operating BWRs shall subnit a report summarizing action taken in response to the above items within 10 days of the date of this Bulletin Supplement.
Accordingly, you are requested to provide within 10 days as specified above, written statements of the above information signed under oath or affirmation.
Reports shall be submitted to the Director of the appropriate NRC Regional Office and a copy forwarded to the Director, Division of Reacter Operations Inspection, NRC.
Office of Inspection and Enforcement, Washington, D.C.
20555 Approved by GAO, B180225 (R0072); clearance expires July 31, 1980. (Application for renewal pending before GA0.) Approval was given under a blanket clearance specifically for identified generic problems.
l
IE Bulletin No. 80-17 August 22, 1980 Supplement 3-RECENTLY ISSUED IE BULLETINS Bulletin
.No.
Subject Date Issued Issued To 80-20 Failures of Westinghouse 7/31/80 To each nuclear Type W-2 Spring Return power facility in to Neutral Control Switches your region having an OL or a CP 80-19 Failures of Mercury-7/31/80 All nuclear power Wetted Matrix Relays in facilities having Reactor Protective Systems either an OL or a CP of Operating Nuclear. Power Plants Designed by Combus-tion Engineering 80-18 Maintenance of Adequate 7/24/80 All PWR power reactor Minimum Flow Thru Centrifugal facilities holding OLs Charging Pumps Following and to those PWRs Secondary Side High Energy nearing licensing Line Rupture Supplement 2 Failures Revealed by 7/22/80 All BWR power reactor to 80-17 Testing Subsequent to facilities holding OLs Faildre of Control Rods to Insert During a Scram at a BWR Supplement 1 Failure of Control Rods 7/18/80 All BWR power reactor to 80-17 to Insert During a Scrar.
facilities holding OLs at a BWR 80-17 Failure of Control Rods 7/3/80 All BWR power reactor to Insert During a Scram facilities holding OLs at a BWR 80-16 Potential Misapplication of 6/27/80 All Power Reactor Rosemount Inc., Models 1151 Facilities with an and 1152 Pressure Transmitters OL or a CP with Either "A" or "0" Output Codes 80-15 Pcssible Loss 'f Hotline 6/18/80 All nuclear facilities With Loss Of Off-Site Power holding Ols 80-14 Degradation of Scram 6/12/80 All BWR's with an Discharge Volume Capability OL l
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