ML19338F272
| ML19338F272 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Vermont Yankee, Quad Cities  |
| Issue date: | 10/09/1973 |
| From: | Lester Tripp US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Reinmuth G US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19338F268 | List: |
| References | |
| NUDOCS 8010140669 | |
| Download: ML19338F272 (4) | |
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UNITED STATES ENCLOSURE 3 O
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n OCT 9 Ul3
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G. W. Reinmuth, Chief, Technical Assistance Branch, RO BWR FUEL FAILURE EXPERIENCE g
[J An analysis of the recent General Electric (GE) fuel failure experience 6
in Dresden 3 by RO indigated a strong dependence on local power.1
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During a fuel QA inspection at Co=monwealth Edison by L. Tripp and p
D. Pomeroy on September 27-29, 1973, additional information on these
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fuel failures was obtained which indicates that operating BWRs may have a generic fuel perfor=ance problem.
This additional information is
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discussed below.
Originally, Dresden 3 was scheduled for a shutdown for a poison curtain removal at a burnup of 47,500-8,500 m:D/:ITU (fall of 1973) with the first refueling scheduled at a burnup of 12,700 m Dh1TU (fall of 1974).
As a result of fuel failures and offgas limitations, Dresdan 3 was refueled in the spring of 1973 at a core burnup of $6000 ETD/IITU.
Prior to this refueling, the reactor was derated to stay within the technical specification limit on stack release rates.2 At the spring refueling, all of the assemblien were sipped outside the core with 103 of the 724 assemblies identifed as lenkers.
Approximately one-half of the leaking assemblics were replaced with new fuel and the re=aining assechlies were reconstituted.
Commonwealth Edison with GE has identified many of the observed Dresden 3 fuel failures as power related.
That is, these failures appear to be ceused by local fuel-clad interaction due to centrol rod movement and
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resultant changes in local fuel rod linear heat rating (kw/ft). The axial location of failure has been correlated with the axial location where movement of the control rod results in the largest step increase in linear power rating.
Calculations have shown that control rod motion of as little as one step (six inches) could increase the local
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linear heat ratings by as much as 30 to 407..
According to Commonwealth Edison representatives, General Electric was " shocked" by the failures observed in Dresden 3.
They indicated that GE was " backing away" from their previous arguments that such failures were largely due to cladding ductility variability resulting in a small, but statistically significant, number of fuel rods in which local strains exceeded the failure capability of the irradiated cladding.
1 September 12, 1973 memorandum, Tripp to Reinmuth.
2 Based on the 105,000pci/sec 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> (avg) limit.
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_g O. W. Reinmuth.
OCT 9 V3
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Co::rnonwealth Edison also suggehted that fuel failures of this type may i=i=#=
have occurred in other BWRs such as Nine Mile Point and Oyster Creek
== 5 which also had a substantial number of failures.
In fact, they suggested M M that such failurcs may have been occurring for some' time in many EWRs
- j[:,[.y but were obscured by moisture related failures (internal hydriding).
a-g As a result of the observation of failures at Dresden 3 (and perhaps
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other plants), GE has made dramatic increases in the projected number
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of fuel failures and offgas release rates in Commonwealth Edison BWRs.
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In addition,, GE appears to have codified Wilmington fabrication schedules
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to fabricate as many 8x8 fuel assemblics as quickly as possible for use as reload fuel.
Finally, GE is reco= mending to utilitics that g
their EWas be base loaded and/or to take all pouer changes slowly j
including extensive utili::ation of flow control.
In addition, GE is f
reco= mending a " pre-conditioning" period in which the power is increased
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at 1/2% per hour and all nodes are brought to as high a power level f
as they would see in subsequent operation. Af ter " pre-conditioning",
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the reactor power could then be changed at the desired rate.
Despite these recommendations Commonwealth has still found it necessary to control #.
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the rate of power change to avoid increased offgas release rates.
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" pre-conditioning" periods have to be repeated every 2to 3 months.
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General Electric is said to be developing analysis methods to predict future failure locations as well as incipient failures.
This model does not yet appear ready for application.
Cor:nonwealth Edison representatives said that GE needs one more refueling outage at Dresden 3 to obtain additional data with which to normalize this model.
As a result of increased fuel failures resulting from the nbove mechanism,;..
Commonwealth Edison has revised the refueling schedules for their
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operating EWRs.
This is the result of the assumption that offgas s
release rates will be much higher, that additional and earlier shutdowns 3
will be needed to replace failed fuel, and that more failed fuel will have to be replaced than originally planned.
Despite revised refueling plans, possible deratings are expected to prevent stack release rates from exceeding technical specifications limits.
Specific revised refueling plans by plant are listed below:
Dresden 1 - The Dresden 1 core consists of two reload batches of GE and three reload batches of GUNFC supplied fuel.
At the present tiee,
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l Dresden 1 is running at low power (%30%) with an extremely high offgas release rate considering the power level (s40, 000pci/sec). A planned refueling outage is to start on October 7, 1973. At that time, they
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plan to do out-of-core sipping (this will be the first out-of-core
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sipping performed at Dresden 1).
At this refueling, Coc=onwealth yl
- crpects to find 60-70 failed assceblies out of 464 total.
Only 50 new
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fuel assemblics have been ordered. GUNFC will be doing the sipping 3
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(with new equipment) and wants.to do a recor.stitution, if necessary.
.3 Commonwealth has reserved the right to make the decision on the
==EE acceptability of reconstituted fuel assemblies until af ter the N=5 reconstitution is made.
FI Dresden 2 - The next refueling of Dresden 2 is presently scheduled bb5 for the fall of 1974.
At that time, the caximum projected offgas
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at full power is %200,000* pCi/sec.
This refueling is to be with
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124-136 new 8x8 assemblics.
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Dresden 3 - Dresden 3 is currently close to netivity limits as the result of failed fuel.
The next refueling shutdown is planned for January 15, 1974. At that time, Coc=onwealth will have forty-four 8x8 assemblics and sixty 7x7 assemblics available.
Quad Cities Quad Cities 1 has been limited in power level by
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activity levels due to failed fuel since August 1, 1973. The first
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refueling outage is scheduled for March 15, 1974 with 488-92 new
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8x8 assemblies. At that time, the maximum projected offgas at full
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power is %250,000*pci/sec.
Commonwealth is planning to operate n'=
Quad Cities in a derated mode until this refueling.
Quad Cities 2 - General Electric has always focused on Quad Cities 2 as the fir 1t GE reactor in which hydriding type fuel failures were expected to be minimal.
Now, primarly as a result of fuel failures
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by the interaction mechanian, GE is also expecting significant fuel
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failures in Quad Cities 2.
(In fact, the offgas increased by approxicately a factor of three on September 22, 1973).
The first.
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refueling outage for Quad Cities 2 is presently scheduled for the.
~T fall of 1974. At that time, the maximum project 2d offgas si. full
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power is s120,000*pci/sec.
Quad Cities 2 is to be refueled with 72-104 new 8x8 assemblies.
2 At the conclusion of our inspection, Pomeroy briefly explored with Co=monwealth Edison representatives the desirability of reporting Dresden 3 fuel failure experience and the results of their subsc-quent analyses.
He pointed out that, if_ this was considered as an
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unusual occurrence or as a significant deviation from expeated
- q performance, Dresden 3 technical specifications would require
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- We believe that these projeci:cd numbers are the sum of the six principal nuclid-djusted for a nominal 30 minute decay'in
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accordance with GE practice.
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h G. W. RU.Muth OCT 9 W3
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reporting. Whether or not Coc:monwealth considered this experience as a reportabic item, they were encouraged to issue a repcrt on the Dresden 3h.2gg experience because of its significance to the industry.
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_Recocmendations
===r; In su= mary, this recent GE fuel failure experience has shown the power i
related interaction type fuel failures are core numerous and significant
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than previously suspected.
It is recommended that:
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R0 Region III obtain a commitment from Co=monwealth Edison to
.h report on Dresden 3 results including the impact of these results P " = -
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on projected fuel failure experience, offgas releases, refueling, and mode of operation of Dresden 1, 2 and 3 and Quad Citics 1 and 2. [In preliminary discussions (Silver-Pomeroy-Oct. 1), DL agrees that a report should be submitted and recommends that RO pursua this with the licensee.]
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Tripp and Pomeroy meet with General Electric at the earliest possible date to pursue the generic icplications of the Dresden 3
( and other recent) GE fuel failure experience.
GE should be asked to review BUR operating experience portaining to the interaction l
failure mechanism as well as applicabic test experience and post-l 1rradiation examinations.
Analytical models under development by GE should be reviewed as well as proposed operational codes to preclude and/or einimize fuel failures of this type.
3.
The current reconstitution at Vermont Yankee (scheduled to have
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started September 28), Dresden 1 and 3 reftelings scheduled within the next few months, and o'ther pertinent refuelings and failure experience in BURS be closely conitored and analyzed by R0 personnel to assess the magnitude of this apparent generic GE fuel perfor=ance problem.
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L. E. Tripp Nuclear Fuels Engineer Technical Assistance Branch, RO cc: D. L. Pomeroy
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