IR 05000461/1990012
| ML20043F121 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 06/04/1990 |
| From: | Lanksbury R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20043F109 | List: |
| References | |
| 50-461-90-12, NUDOCS 9006140177 | |
| Download: ML20043F121 (13) | |
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' 9 Ul'S, NUCLEAR REGULATORY COMMISSION
REGION III
i Report No. ' 50-461/90012(DRP)
Docket No.
50-461 License No.
NPF-62 i
Licensee:
Illinois Power Company 500 South 27th Street Decatur, IL 62525 Facility Name:
Clinton Power Station i
Inspection At:
Clinton Site, Clinton, Illinois Inspection Conducted: May 18 - May 31, 1990 Inspectors:
P. G. Brochman P. R. Pelke S. P. R
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Approved C. D.
a y, Chhf (,el4 % c Reactor Projects Section 3B Dat'e
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Inspection Summary Inspection from May 18 -- May 31,1990 (Report No. 50-461/90012(DRP))
l Areas Inspected:
Special, unannounced safety team inspection by the resident
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and region based' inspectors.of circumstances surrounding two events. The
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first event involved a-design deviation which occurred during' original l
construction,' in which tie rods were not installed on bellows which connect the shutdown service water piping to the division I and II emergency diesel.
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generators _The second event involved errors in repositioning the= shutdown-service water isolation valves for the diesel generator heat exchangers, which ha_d been shut to repair the bellows described above,- and resulted in cooling
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Results:
Both of these events were of safety significance. The missing tie rods allowed the bellows to expand beyond the design limits and to induce-stresses in the safety-related piping and supports which exceeded American
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Society-of Mechanical Engineer's Boiler and Pressure Vessel-Code limits due to t
thermal.and hydraulic forces. The licensee had not yet completed an analysis of this event which was to include the added effects of a seismic event which may have resulted in exceeding code allowable stresses even further. The second event resulted in cooling water to both division I and II emergency i
diesel generators being isolated.
The diesel generators would have been
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unable to perform their design function, had an actual event occurred, without rapid operator intervention. The second event was of more concern because-it had the potintial, to lead to failure of the diesel generators, during an actual-event (emergency core cooling system actuation coincident with a loss s
9006140177 900605
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{DR ADOCK 05000461 PDC
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I of off-site power), ~ unless operator's intervened. The licensee had~not yet completed an analysis of this event to determine how long_the diesel-generators could have run without the cooling water before being permanently.
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DETAILS l,
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1.
Persons Contacted
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Illinois Power Company (IP)
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- J. Perry, Vice President
- J. Cook, Manager - Clinton Power Station
- R. Wyatt,. Manager - Quality Assurance J. Miller, Manager - Nuclear Station Engineering
- F. Spangenberg, III, Manager - Licensing and Safety R. Morgenstern, Manager - Scheduling and Outage Management J. Palmer, Manager - Nuclear Training
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J. Palchak, Manager - Nuclear Planning and Support
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D. Morris, Director.- Plant Operations S. Rasor, Director - Plant Maintenance l
D. Holtzscher, Director - Nuclear Safety
- R. Phares, Director - Licensing S. Hall, Director - Nuclear Program Assessment K. Baker, Supervisor, I&E Interface
- A. Ruwe, Director, System and Reliability Engineering
- R. Gill, Manager, Projects and Assessment
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The inspectors also contacted and interviewed other licensee and contractor personnel during the course of this inspection.
- Denotes those present during the exit interview on May 31, 1990.
2.
-Purpose (71707 & 93702)
The purpose of this special team inspection was to review the
circumstances surrounding two events.
The first event involved the
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discovery on May 8,1990, that the installed configuration of the -bellows on the shutdown service water piping to the division I and II emergency
. diesel generaturs (DG) was not consistent with the specified design
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configuration (tie rods were missing).
Second, on May 11, 1990, during restoration of the isolation for work on the expansion bellows, the DG heat exchanger shutdown service water (SX)
outlet valves were not manipulated correctly.
This resulted in the valves being in the shut position, vice throttled open. Consequently, when the division I DG was started for a surveillance test it tripped on high jacket water temperature.
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The inspectors interviewed operating and technical personnel and management involved in each event. The inspectors developed a chronology for each event and analyzed each event for its safety implications.
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Unanalyzed Condition in Division I and II Emergency Diesel Generators due to Missing Tie Rods on Shutdown Service Water Bellows
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Description of Event
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On May 8, 1990, the licensee identified.that tie rods on bellows connecting the division I and II emergency diesel generator heat.
exchangers to the associated shutdown service water piping were'not-installed.
There was a bellows on both the inlet and outlet SX pipes for each of the two tandem diesel engines on each of the division I and II diesel generators for a total of eight bellows.
The bellows were installed to isolate vibratory motion between the
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SX piping and the diesel generators. The tie rods had been
installed by the vendor to limit bellows expansion.
The licensee
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~ determined that the tie rods had been removed by mistake during (
original construction in'1985.
When the licensee determined that
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design pipe stress calculations had been based on having the tie i
rods in place and noted significant lateral expansion-of the bellows and visible displacement' of the attached SX piping, they declared both the~ division I and II diesel generators inoperable due to being-i in an unanalyzed condition. The licensee-commenced a controlled-shutdown of the reactor in accordance with Technica1' Specification Action 3.8.1.1.g and declared a Notification of Unusual Event (NOVE).
Hot Shutdown was achieved and the NOVE was terminated on May 9, 1990.
b.
Sequence of Events Early 1985 Various construction travelers were issued documenting removal of what were apparently thought to be-temporary attachments and shipping lugs from
the bellows during installation of the bellows _in the SX piping.
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May 2, 1990-
.The diesel generator _ system engineer identified that one of the bellows on the division I diesel had-a small leak.
Condition Report 1-90-05-017 was I
initiated.
The condition was determined to have no
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impact on system operability'.
May 3, 1990 Repair options for the leaking bellows were evaluated. A Parker bellows, procured to replace the existing Pathways bellows was located onsite.but was not a like-for-like replacement.
Field Alteration package SXF018 was initiated to analyze the Parker bellows and authorize its use.
May 4, 1990 As part of the design work for Field Alteration.
SXF018, an engineer did a field check of the as-built dimensions of the bellows.
He found that the leaking bellows was longer than the original length shown on
the vendor's drawing. He,also noted that the existing Pathway bellows did not have tie rods,
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although the replacement Parker bellows did.
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Discussions were held with the vendor to try to determine the significance of'the missing tie rods and an investigation was initiated to find documentation justifying the removal of the tie rods.
- The licensee stated that the vendor indicated that
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the tie rods were not required but were recommended.
A review of Seismic Qualification package SQ-CL204 for tbn bellows did not mention whether tie rods were installed in the qualification tests.
May 7, 1990 Engineering measurement of other uninsulated bellows showed them ta be extended laterally. A maintenance work request was initiated to remove-insulation from the remaining bellows. The bellows on the division III diesel generator were noted to L
have their tie rods installed.
The bellows vendor-started to perform stress calculations for the as-found bellows dimensions.
May 8, 1990 8-12:00 a.m.
After insulation removal, Engineering took i
measurements of the remaining bellows and forwarded the information to the vendor.
The vendor provided design approval for the stretched bellows bi:4 recommended that tie rods be installed.
Sargent and Lundy Engineers, Inc. (S&L) were asked
to formally check the pipe stress calculations.
A maintenance technician identified that one of the SX piping struts on the division I diesel generator was bent.
Baldwin Associates Construction Travelers were located-that authorized the removal of' the lugs for
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the tie rods because the lugs were assumed to be
lifting lugs for shipping purposes.
2:00 p.m.
S&L stated that their original pipe stress design
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calculations were based on having the tie rods in place.
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l S&L and Illinois Power engineers started walking down both the division I and II diesel generator SX piping L
systems to look for damage.
y 2:10 p.m.
Condition Report 1-90-05-028 was written to document the missing tie rods.
The Shift Supervisor considered the operability of the diesels unkncwn pending completion of the S&L evaluation.
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Field'walkdowns noted that the division II SX pipe was raised off;its sliding support.
Condition Report-1-90-05-029 was written to document bent strut and raised support.
5-7:00 p.m.
Based on the field 'walkdowns', which also showed that some supports were out of angular alignment, and'
the fact that S&L piping stress calculations would not be available for two days, a management decision was made to declare both of the diesels inoperable.
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I 6:40 p.m.
The Shift' Supervisor declared both'the division.I and II diesel generators inoperable due to being in
The. plant entered the two hour Action requirement of Technical Specification 3.8.1.1.g.
The.NRC Resident Inspectors were-notified
of the diesel inoperability.
.j 8:40 p.m.
A controlled shutdown was started in accordance t
with Technical Specifications. A NOVE was declared i
due to commencing a shutdown required by Technical Specifications.
9:21 p.m.
The NRC was notified via the Emergency Notification System of the NOUE and shutdown, u
May 9, 1990
1:00 a.m.
The initial S&L pipe stress calculations were completed.
'7:26 a m.
The reactor was manually scrammed from about 25%-
power to complete the shutdown to' Operational Condition 3 (Hot Shutdo'wn).
-8:00 a.m.
The NOVE was terminated, a
May 10, 1990 The plant entered Operational Condition 4 (Cold Shutdown).
c, Evaluation and Analysis
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The licensee's response to the event was conservative and in accordance with Technical Specifications.
Engineering support in determining-the correct configuration-of the bellows and in
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identifying the cause'and significance of the missing tie rods was good.
Management' involvement in the event was very evident. -The management decision to declare the diesel-generators inoperable was based on the combination of a known deviation from the design and observed piping displacement and damage to a support.
Later
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analysis showed that code allowable yield stresses may have been
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exceeded at some points in the SX piping system, although the licensee determined that actual yield stresses were not exceeded based on a review of the certified material test reports for.the components in those areas.
This event was considered to be potentially safety-significant-because the division I and II diesel generators had a design deviation that had existed since initial pl_ ant licensing, that
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could have allowed the required SX piping systems on both diesels
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to fail. However, the licensee determined that the. actual piping system materials would not have-failed under normal operating
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conditions because the materials' had higher-than code required yield strengths. Whether.the SX piping systems could have failed-under seismic conditions was still to be determined.
-The root cause of the design deviation appeared to be a misunderstanding of the purpose of the tie rods during initial construction. The rods were apparently thought to be shipping bars
and the. lugs were thought to be lifting lugs.
These devices were removed after the bellows were installed, Similar rods on the division III diesel generator were not removed.
However, the division III diesel generator was installed at a different time
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than divisions I and II.
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Contributing causes for the event were inadequate drawings and instructions from the vendor.
The installation instructions portion of the Pathway vendor manual had a sketch of a bellows with shipping bars and lifting lugs.
The drawing did.not show tie rods. Associated installation instructions did not mention the existence of tie rods but did say to remove the shipping bars after installation.
In addition, of the 46 safety-related bellows in the plant, only those bellows on the diesel generator service water piping were designed
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to have tie rods.
There were.-no tie rods on any other safety-related t
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The licensee had performed an analysis of all safety-related bellows
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in response to Violation 461/82020-01 in early 1983.
That analysis-concluded that tie rods were required on the diesel generator SX bellows. However, at that time, the bellows had not been installed, so a field verification of the tie rods could not be done.
10 CFR 50, Appendix B, Criterion III, " Design Control," required, in part, that measures be established to assure that applicable regulatory requirements and the design basis, are correctly translated into specifications, drawings, procedures, and instructions. ' Adequate measures were not established during construction of the division I and II diesel generators and their associated shutdown service water piping systems in or about 1985 to assure that the requirement for-the installation of bellows tie rods required by the design basis
.ss correctly translated into installation drawings and instructions.
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As e result, the division I and II diesel generator service water piping systems did not meet their design basis requirements from
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the date of issuance of the low power license on_ September 29, 1986, until May 8, 1990.
This is an apparent violation of 10 CFR 50'
Appendix B, Criterion III (461/90012-01(DRP)).
d.
Licensee's Corrective Actions The inspectors attended the licensee's critique ~of the event and followed the licensee's corrective actions throughout the event.
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Major corrective actions consisted of the following:
(1) The division I and II diesel generators were declared inoperable-
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and the actions of Technical Specification 3.8.1.1 were carried
out.
(2) A NOVE was declared when the shutdown was started and the NRC
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was notified.
The NOUE was terminated when the plant reached Hot Shutdown.
The licensee submitted letter U-601671 to the NRC on May 15, 1990, as a summary report of the NOVE.
(3) Stress analysis was performed for the bellows with no tie rods to determine worst case (without seismic) loads on the piping system. That analysis identified five piping system areas-l where code-allowable yield stresses could have been exceeded.
Those five areas were compared to the certified material test'
reports to verify that actual material yield stresses would not have'been exceeded.
(4) Walkdowns were conducted to identify all areas which appeared'
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to be displaced.
Analysis was conducted for all questionable foundations, supports, embedments, auxiliary steel,_etc.
All
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areas were evaluated as acceptable.
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(5) The leaking bellows was replaced with the Parker bellows
containing tie rods. The other seven bellows were returned to-
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their. design configuration with lugs and tie rods installed.
(6) Twenty-six pipe-supports were-adjusted to design alignment tolerances. One support could not be returned to tolerance and was evaluated as acceptable. The bent pipe strut was' replaced.
and other repairs were made to correct minor' deficiencies in piping. supports.
(7) Engineers observed piping movement during initial system pressurization to assure that no excessive displacement
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occurred.
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L (8) The licensee intended to submit a Licensee Event Report to the.NRC within 30 days of the event.
(9) The licensee was reviewing the safety significance of the
missing tie rods under expected operating and seismic loads.
This evaluation was expected to be completed by June 15, 1990.
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Diesel Generator Heat Exchanger SX Isolation' Valves Incorrectly
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Repositioned After Maintenance Which Resulted in a lack of Cooling Water I
to the Division I and 11 Diesel Generators a,
. Description of the Event To provide isolation for the work on the bellows described above, the licensee danger tagged shut the SX inlet and outlet isolation valves to the division I and II diesel generator heat exchangers.
The inlet valves for_each of the four heat exchangers were normally used as throttle valves to regulate flow.
The valves were 1/4 turn
' butterfly valves with geared handwheels which required several turns -
to open the valve. The valves were also used to provide isolation
for the maintenance on the bellows, Valves ISX005A & B, ISX064A.and i
ISX0658 had caution tags hung on_them which indicated the throttle
position of each valve. These positions had been determined
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previously by the SX flow balancing (see inspection' report
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461/90005(CRS)).
During the process of flow balancing the SX system, the licensee's technical staff developed a methodology to position the throttle valves so as to obtain consistent flow rates.
This method involved i
turning the valve handwheel until evidence of stem movement or flow past the valve seat was noted and then, while opening:the valve, counting the number of turns open until the desired throttle position was reached.
This technique was in contrast to one in which the number of turns open from "hard" shut were counted (i.e.,
i from the beginning of handwheel movement).
This second technique-was found.to not.be repeatable enough to allow for accurate flow balancing, due to considerable slack in the gear train for the n
i valves (more than one full turn of the handwheel).
When the.SX valves were repositioned after maintenance on the
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bellows,-the incorrect method (the second. technique above) was utilized.
Since the positions stated on the caution tags were all i
roughly one turn open, except for valve 1SX0658, the net effect was that-the valves remained closed.
The licensee started up the reactor and entered Operational Condition-2 (Startup) at 10:40 a.m. on May 14, 1990. At 1:35 p.m. on May 15, 1990, the division I diesel generator
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was started for a routine surveillance.
Two minutes after reaching full load, at-1:47 p.m., the diesel tripped on high jacket water temperature due.to'a lack of cooling water, b.
Sequence of Events March 19, 1990 Caution tagout 90-0213 was issued for division I i
of the SX system and each tag specified the throttle position for its associated valve based on the initial flow balancing.
Division I of the SX system was taken out of service to perform a modification to achieve proper flow balancing.
In addition to
stating the valve's position, the caution tags stated that they should remain in place until the permanent valve lineup for SX was revised.
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-March 22, 1990 Division I of SX was restored to operation and-a final flow balancing was performed. As a result, the
throttle positions for valves ISX005A.and ISX064A
'were changed;.however, the caution tags were not
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revised to indicate the new throttle positions.
April 07,1990 Caution tagout 90-0302 was issued for division II
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of SX and utilized interim positions for valves-ISX005B and ISX065B. The caution tags were annotated with words similar to division I regarding removal.
April 16, 1990 A memorandum was sent from the plant technical
staff to the operations department which contained
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the final, correct, positions for'all throttle valves in.SX divisions I, II, and III.
This information.was not incorporated into caution tagouts 90-0213 and-90-0302.
L May 9, 1990 The SX throttle valves for the division I and II
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diesel generators were danger tagged closed in order to perform maintenance on the bellows to restore them to their design condition.
May 11, 1990 Division I and II SX valves to the diesel generators were restored to their throttle position, in accordance
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with caution tagouts 90-0213 and 90-0302 (incorrect position still specified on the tagouts).
This would have resulted in the valves being too far open, which, while not-affecting the diesel -generators, could.have reduced the flow rates-to other SX components, However, r
an additional error occurred in that the operator who '
l positioned the valves, utilized the wrong methodology-
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-(turns open from hard shut vice-turns open from valve disk beginning to move).
In this event, the operator-had questioned the assistant shift supervisor on what was the correct method to position the throttle valve,
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but he received incorrect guidance.
As a consequence of this. error, and the slack in the-
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. gear train for the valve operator, the SX flow to three-i of the four diesel engines was isolated, rendering
the' division I and II diesel generators inoperable.
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May 14, 1990 The unit was in Operational Condition 4 (Cold Shutdown) and a reactor startup was commenced.
Operational Conditi~on 2 was entered at 10:40 a.m.
May 15, 1990
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1:35 p.m.
The division I diesel generator was started for a routine surveillance.
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L 1:45 p.m.
The diesel generator reached rated load.
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The diesel. generator tripped on high jacket water j
temperature due to a lack of cooling. The maximum Jacket water temperature reached was 208 F and the maximum lubricating oil temperature reached was 190 F.
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'2:00 p.m.
The low flow condition.was identified and division I-valves ISX005A and ISX064A were repositioned to the values specified on caution tagout 90-0213 (an incorrect value).
-2:32 p.m.
The division II. valves ISX005B and ISX065B were
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repositioned to the values specified on tagout
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90-0302 (an incorrect value).
6:00 p.m.
Valves ISX05A & B, ISX064A, and ISX065B were repositioned to their correct throttle positions after the existing valve positions were reviewed by the technical staff.
8:40 p.m.
An operability surveillance was completed satisfactorily for the division III diesel generator, t
11:38 p.m.
An operability surveillance was completed satisfactorily
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for the division II diesel generator,
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May 16, 1990 6:30 a.m.
.An operability surveillance was completed satisfactorily!
for the division I diesel generator.
Ma'y 26, 1990 A permanent procedure change for the SX system'-
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lineup was issued which incorporated the final flow
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balancing positions.
The caution tags were; removed.
c.
Evaluation and Analysis Technical Specification 1.27 required, in part, that a syst'em,-,
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subsystem, train, component. or device be OPERABLE or have OPERABILITY when it is capable of performing its specified function (s) andWn all necessary attendant cooling or other auxiliary equipment: that are required for the-system to perform its function (s) are also i
capable of performing their related support function (s).
Technical Specification 3.0.4 required that entry into an OPERATIONAL CONDITION or other specified-condition not be made unless the conditions for the Limiting Condition for Operation
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are met'without-reliance on provisions contained in the ACTION-requirements.
Technical Specification 3.8.1.1.b required, in part, that three separate and independent diesel generators be OPERABLE while in OPERATIONAL CONDITIONS 1, 2, or 3.
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The improper operation of.the SX valves resulted in shutdown service water to the division I and II diesel engine heat exchangers being isolated.
The SX system directly cools the jacket water system for each engine and indirectly cools the lubricating oil system for each engine (via the jacket water system). With the shutdown service water isolated, the division I engines ran for only 12 minutes, of which 2 minutes were under full load, before : ripping on high jacket water temperature on the 16 cylinder diesel engine. With the
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shutdown service water isolated the. Jacket water would begin to boil'away. The diesel may have been able to continue to operate while the jacket water was boiling.
However,'when a significant amount of the jacket water was boiled-off the cylinder walls, heads, and lubricating oil temperatures would all rise rapidly resulting in failure of the diesel generator when the pistons or bearings seize.
Without_the necessary support system of shutdown service water the diesel generator could not perform its design function.
Consequently, s
it was inoperable,- During normal operations, a high jacket water
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temperature would trip the diesel generator. However, if the diesel generator started under Loss of Coolant Accident (LOCA) conditions, the high jacket water temperature trip was bypassed.
Consequently,
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a high Jacket water temperature would not cause a trip but would alarm a specific annunciator at the diesel generator's local control panel and a general diesel generator trouble annunciator in the main control ' room. With division I and II diesel generators inoperable, action statement'g of Technical Specification 3.8.1.1 applied.
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Consequently, entry into Operational Condition 2 was not allowed by_ Technical Specification 3.0.4.
The entry into Operational Condition 2 at 10:40 a.m. on May 14, 1990, with division I and II.
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diesel generators inoperable, was an' apparent violation of Technical Specification 3.0.4 (461/90012-02(CRP)).
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At the conclusion of this inspection the licensee had not yet established the length of time the diesel; generators could operate without cooling water.
Rapid operator actions would have been
. required to restore cooling water to the diesel generators in the case of an emergency in which.the diesel generators were required to operate.
It took approximately 13 minutes from the
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time a diesel generator trouble alarm was received until cooling water was restored to the division I diesel generator during the event of May 15, 1990.
During that event, an operator was present locally at the diesel.
In the case of an unexpected event such as a LOCA with a loss of offsite power, operators may not have been able to restore cooling to the diesel generators in time to prevent engine damage.
-The problems with the interim versus final' valve positions did not contribute to this event. Nevertheless, it was an indicator of the effectiveness of the licensee's efforts to ensure that the SX system could be restored to a balanced condition following manipulation of the valves.
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Licensee's Corrective Actions In response to-this event, the licensee implemented the following
corrective actions:
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'(1) Other tagouts were reviewed to determine if similar problems with throttle valves existed.
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(2) The SX tagout was compared to the final flow balancing i
positions to ensure no other problems existed.
L (3) The DG vendor was contacted to obtain information on actions to be taken to assure the diesel was not damaged.
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(4) The licensee issued the permanent procedure revision.to the SX valve lineup and removed the caution tags.
Additionally, the following long term actions have been identified:
(1) Determine a method to ensure long term repeatability of
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throttling valve positions, t
(2) Provide training to operators on this event and methods to be used in throttling these and other valves.
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Conclusions Both of the events' described in this report had potential safety r
significance and involved circumstances where' equipment designed to
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mitigate'the' consequences of accidents could-have failed to perform their design functions.
The actual safety significance of the missf ng bellows tie rods depends primarily on the results of an analysis of the effects of. seismic loads on the SX piping and supports. _That analysis-was not
- complete at;the time this report was written.' The' actual safety significance of the SX valve mispositioning. depends primarily on a
~ determination of the-. length of time the diesels could have operated without' cooling. water and the likelihood of operators being able to restore cooling before engine damage occurred.
That determination was also not completed at the time of this' report.
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6.
Exit Interview (30703)
.The inspectors met with the licensee representatives denoted in
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paragraph I at th'e conclusion of the inspection on May 31, 1990. The
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inspectors summarized the purpose and scope of the inspection and the
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findings. The inspectors also discussed the likely informational content of the inspection report, with regard to documents or processes ret %ed
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by the inspectors during the inspection. The licensee did not idenofy
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'any such documents or processes as proprietary.
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