ML20024G603
| ML20024G603 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/28/1975 |
| From: | Choules N, Little W, Maura F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20024G600 | List: |
| References | |
| 50-263-75-13, IEB-75-04, IEB-75-4, NUDOCS 9102130467 | |
| Download: ML20024G603 (12) | |
See also: IR 05000263/1975013
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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OFFICE OF INSPECTION AND ENTORCDiDIT
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REGION 111
Report of Operations Inspection
IE Inspection Report No. 050-263/75-13
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Licensect
Northern States Power Company
414 Nicollet Mall
Minnenpolis, Minnesota
55401
Monticello !!ucicar Generating Plant
License No. DPR-22
Monticello, Minnesota
Category:
C,
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Type of Licensee:
GE 14'R 545 Mh'c
Type of Inspection:
Special, Announced
Dates of Inspection:
July 8, 9 and August 18 and 19, 1975
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Principal Inspector:
. Itaura
(D'te)
A e/ J //
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Chnt'l en p
~8 2M yf
N./8-9/75)'
7(Date)
Accompanying Inspector:
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Other Accompanying Personnel:
B. Sienci
(7/8-9/75)
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R. Heyer
(7/8/75)
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Reviewed Byl
W.S.LYttic
~T 2 T
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Senior Inspector
[(Date)[
Nuclear Support Section
Reactor Operations Branch
9102130467 750829
ADOCK 05000263
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SUNHARY OF TINDINGS
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Inspection Summary _
An inspection was performad on July 8, 9 and August 18, 1975, (75-13)
regarding the gross fuel failure experienced by the licensee, and on
August 18 and 19, 1975, regarding follovup actions taken by the licensee
with regards to IE Bulletins No. 75-
75-04A and items identified
intheinitialfirestopinspection.gpandNo.
Two deviations were identified
concerning licensee commitments to seal electrical penetrations and
perform a review of fire detcetion sensor and fire hose station
locations.
Enf orc emen t Itemn
None.
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Licennec Action on Previously Identified _ Enforcement items
Not Inspected.
Other Sitnificant items
A.
Systems and Components
1.
The licensee has been experiencing gross failures in the original
batch of 7 x 7 fuel.
The off-gas activity rate at the SJAE
has approached 8 x lo pCi/sec. ' ThW*1teensee plans to replace ~ s."
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all remaininc originni 7 x 7 fuel with the new 8 x 8 fuel.
The
. failures appear to be pCI originated.
2.
Considerable work is still required to bring all electrical
penetrations up to specifications.
B.
Facility Items (plans and Procedures)
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Not applicable.
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C.
Managerial items
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Not applicabic.
D.
Noncompliance Identified and Corrected by Licensee
Not applicabic.
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IE Inspection Rpt No. 050-263/75-08.
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E.
Deviations
1.
Contrary to Section 8 of the FSAR as implemented by Bechtel
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Dws M-636, Revision 0 issued for construction on February 13,
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1970, several of the cable penetrations between the cable
spreading room and the control room are scaled with styro-
foam instead of the specified polyurethane.
(paragraph 2,
Report Details)
2.
Contrary to the commitment made in their response to IE
Bulletin No.75-04A,. dated June 30, 1975 the licensee has
not performed a review of fire detection sensor and fire
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hose station locations to verify adequate coverage of all
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areas where a fire would have a high safety significance.
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(Paragraph 3.f. Report Details)
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Status of Previously Reported Unresolved Items
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Not applicable.
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Management Interview
A management interview was conducted with Messrs. Larson, Plant ibnaccr;
Clarity, Superintendent, Plant Engineering and Radiation Protection; and
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Antony, Plant Engineer, Operations at thef conclusion of the inspection
on August 19, 1975.
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A.
The inspeator noted that considerable vorbases st.111 required ,w%m
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to bring all penetrations to specifications. For example; the
modified off-gas cabic penetrations in the control room have no
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fire steps, and several penetrations in the cabic spreading room
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ceiling were noted to have styrofoam instead of polyurethane.
This constitutes a deviation from construction specifications.
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One-hundred percent inspection of all penetrations by the if censco
will be required.
This is planned by'the licensee, and to ensure
none are missed the licensee plano to use the drawings showing all
penetrations on a checklist.
(Paragraph 2, Report Details)
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B.
The inspector noted that a commitment to NRC due August 1, 1975
had not been completed. He indicated that whenever commitnehts
cannot be carried out as scheduled it is the licensee's res'pon-
sibility to inform NRC in advance of the schedule slippage.
The licensee indicated it is their intention to update their response
to Bulletin No.75-04A monthly, but such updating was not due until
the end of August.
At that time they planned to notify us of the
delay in the commitment.
(Paragraph 3.f. Report Details)
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C.
The inspector stated that there is no disagreement between tGC's
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and the licenson's records on the fuel failures observed last
July. The difference between our records and CE's could be due
to interpretation of the observations.
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REPORT DETAILS
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1.
Persons Contacted
Northern States Power Company (NSP1
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- G. Neils, Concral Superintendent, Nuclear Plant Operations
R. Anderson, Power Production Department
H. Voth Nuc1 car Support Service Department
C. Larson, Plant Manager
H. Clarity. Superintendent, Plant Engineering and Radiation
Protection
D. Antony, Plant Engineer, Operations
D. Nevinski, Nuclear Engineer
J. lieneage, Engineer
R. Perry, Engineer
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General Elcetric Company (CE)
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N. Skarshaug, Field Service, GE Fuels
2.
Visual Examination of Cablo Penttrations
The control room, cabic spreading room and turbine building to
cabic spreading room penetrations were reincpected.
The inspector
noted that
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Very little work has been donc to corryct the deficiencies
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noted during our previous inspection.-
The licensee was
still vaiting for the equipment needed to spray the pyrocrete.
Most of the scaling with pyrotrete must be done in thin
layert, with the : pray equipment becauce of the inaccescibility
of the penetrations.
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b.
The penetrations in the control room used for the modified
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off-gas system cables (approximately 3) have not been scaled.
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c.
Several ponctrations in the cabic spreading room ceiling
have a styrofoam barrier, one-inch thick, instead of th'c
polyurethane.. In most cases the styrofoam has a thin Eoating
of flamemastic.
This is a deviation of approval construction
specifications which specify the scaling material to be
polyurethanc.
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IE Inspection Rpt No. 050-263/75-08.
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3.
Response to IE Bulletin No.75-04A
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The licensee's response dated June 30, 1975, to IE Bulletin No.75-04A was reviewed for completed items.
The following findings
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were madet
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Work instruction 3AV1 4.1.2, Revision 0, dated July 18, 1975
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vas issued defining responsibilities of assigned plant
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engineers with respect to modifications which are designed
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by of f site organizations, including specific responsibilitics
relating to control of installation work.
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The
b.
Special Procedure No. 8053 was issued August 8, 1975.
proceduro covers the sealing and testing of electrical penetra-
tions.
It requires a minimum thickness of 1/4 inch of thermal
insulating mastic applied in layers of approximately 1/8 inch.
It bars the use of ignition sources in the testing of penetrations.
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Directiven applicable to work control are being revised and
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c.
the licensee feels confident the September 1, 1975 commitment
date vill be tiet.
d.
Six of the eight group cafety chairmen have revicued fire
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prevention policies and practices at their group safety
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meetings,
The fire detcetion equipment in the cabic spreading room has
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sot been tested since the. original preoperational test. The
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manuf acturer recommends semi-annual tests involving activation
of detector alarm, check of supervisory circuits and general
inspection of dust.
Also an annual test to measure the
sensitivity of each detector. The licensco plans to write
a surveillance procedure to . include these recommendations.
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The review of fire detection sensor and fire hose station
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location to verify adequate coverage of all areas where a fire
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vould have a high safety significance has not been performed.
This is a deviation f rom a licensee commitment to NRC.
The licensco's Operating Saf ety practices, Part 3,195J.
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paragraph 4.3.11 covers the use of Water Fog Hose Station in -
fighting cicetrical fires.- Distribation of this manual was
discontinued by NSp approximately 5 years ago.
These practices
are to be incorporated in the new Supervicor's Safety Manual,
but this has not been done yet.
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h.
Diagrams showing the preferred sequence of use of the existing
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core cooling systems has been added to the procedures cover-
ing shutdown and cooldown of the core in case of loss of
normal and preferred alternate systems.
1.
The procedure covering shutdown from outside the control room
is being revised. The licensee expects to coepicte this work
by September 1, 1975.
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4.
Self_ Contained Breathing Equipment
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The licensee has contacted his supplier of breathing air cylinders
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and has documented that additional cylinders can be obtained af ter
normal working hours. The names and phone numbers of supplier
personnel for emergency pickups has been made availabic to plant
supe rvisors.
The licensee has also contacted the Monticello, Anoka and St. Cloud
Fire Departments. The Anoka and St. Cloud fire departments can'
help in refilling NSP air cylinders.
The Monticello fire department
can supp?.y fjve " Survive Pack" units and six extra air tanks for
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the unitu in an emergency.
Training of the members of the emergency and fire teams in the use
of the Scott p.escue Pak it. planned to be completed ty August 29, 1975.
5.
Insgector's Observations _{ Fuel _ Innpection July 8.197M
Fo r" assemblies (MID 178, 274i 337, and 423) were visually inspectedb
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with the help of a borescope.
The following observations were notedt
a.
The location of all Intne cracks can be easily spotted by
a lack plume on the c.1 adding.
All other areas are covered
with a redirh oxide filu.
b.
A few small hydriding blisters were noted,
c.
All large cracks were located in corner pins.
d.
Crack vidthe range from haf tline to approximately 1/4 f,nch.
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Crack lengths appear to extend beyond the distance between
two spacers (18 inches).
It is difficult to be exact because
the cracks disappear and reappear f rom behind the fuel pin.
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f.
While some cracks wave,others are fairly straight for a
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distance of at least 6 to 8 inches.
The edge of the cracks vary from ragged to smooth.
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In one area the crack edge was bent outvards approximately
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40 mila.
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A white deposit was noted on the edge of some cracks.
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The cladding was missing in a few small areas, but no where
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did fuel appear to be missing.
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There were no signs to indicate that clad or fuel ec1 ting
had occurred.
6.
R('-iew of Licensce's Data Regardinn Fuci railure
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The inspector obtained data from the.11censee covering:
Core location of all the failed fuel identified through
a.
sipping at the conclusion of cach cycle. This includes
the ten assetblics visually inspected by the licensee
and where large cracks were observed to exist,
b.
The location of the observed cracks in each of the ten
assemblics.
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The ten assemblies average exposure distribution, nodal
c.
exposure distribution and assen.bly control rod histories.
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d.
The average exposure of each fuel assembly at the end of
each cycle.
The average exposure of each assembly (not a leaker) dis-
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charged at the end of each cycle.
f.
Identification of the original 7 x 7 fuel suspected of having
fuci pellet enrichment mix-up.
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A review of all the above data was made in an cffort to deteFaine if
a correlation existed which would explain the failures experienced.
The results of the review indicated that:
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The failures are concentrated in the four corner pins as
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noted in Figure No. 1 belows
(1) Of the 40 corner pins inspected 65% had visibic cracks.
(2) of the 240 outside pins only 14% had visibic cracks.
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(3) of the 80 lowest enrichment pins 35% had visible cracks.
(4) Of the 160 intermediate enrichment pins inspected 4%
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had visibic cracks.
Figure No. 1
Number and Location of Failed Pins
Identifled in 10 Assemblics Inspected
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CONTROL ROD DIADE
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b.
The failures do not appear to be related to fuel exposure
history.
(1) Failed fuci pins range from a low of approximately 6,000
mwd /t to approximately 18,000 mwd /t with most in the range
of 11,000 to 15,000 mwd /t.
One difficulty in making such
a correlation is the fact that the time in Cycle II or III
when a particular fuci pin failed is unknown.
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If one assumes the failures occurred durinC the period
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in which the control rod blade next to the affected
element was totally or partially inserted in the cycle,
then the exposure history narrows to the range of 8,000
to 15,000 nwd/t with most elements in the 11,000 to 13,700
mwd /t range.
(2) One hundred and .orty non lenkers discharged at the end
of cycic II had an average exposure of approximately 13,000
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avd/t and twnty-six non lenkers discharged at the end of
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Cycle III had an average exposure of approximately 15,800
mud /t.
Most f ailurce (56%) appear to be located cxially from six to
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ten feet above the lower tic plate (between fourth and seventh
spaccr) as noted in Figure 2 below:
Figure No. 2
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Percent of Failed Pin Axial Section
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Top of Fuel
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Space Above Lower Tie Plate
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d.
The failure rate for fuel assemblies suspected of having
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fuel pellet enrichment mix-up is higher than for the total
core, but not significantly higher.
(1) The total core failure rate is approximately 33%.
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(2) The failure rate among suspected assemblics is 44%.
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(3) Of the ten assemblies inspected, only five are in the
enrichment mix-up category.
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7. . Vendor's Representative Ponition
According to the vendor's representative these cracks are typical
of pellet clad interaction (PCI) as the primary cause, plus some
minor hydriding resulting as a byproduct.
In addition most fuel failures observed at other facilities have,
been generally experienced on the pins adjacent to the control
rod blades as shown by the shaded area of Tigure No. 3 below.
Few f ailures have occurred on the pin opposite the control blade.
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Figure No. 3
Aren k'here Most Fuel Pin Failures
} lave Ecen Experienced According to CE
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Blade
Alco, thes.c are the first cracks he has seen which extend beyond
the area between two grfd spaecc.,
As noted before the length of
some, cracks is ucasured in feet not inches.
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8.
Licennec's Position
The licensee appears convinced most fuci damage is being caused by
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control rod blade motion. Of special concern to them is the Tech-
nical Specification requirement for veckly CRD cxcrcise tests.
Based on data reviewed the inspector the node irmediately below the
top of the blade experiences a sharp increase in linear heat
generation rate, approximately a factor of three, when the
blade is withdrawn with the reactor operating at high power icvels
(> $ 0%) .
The licensco stated that when rod exercising was being performed at
naar full power the unit had to be derrated at the rate of 10 mut/ day
in order to remain within thn off-gas limit at the SJAE.
If the
exercise was donc at approximately 70% of rated power the rate of
derration dropped to approximately 2.5 mut/ day.
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