ML19340A792
| ML19340A792 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/25/1977 |
| From: | Creswell J, Little W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML19340A791 | List: |
| References | |
| 50-010-77-04, 50-10-77-4, 50-237-77-04, 50-237-77-4, 50-249-77-04, NUDOCS 8009030831 | |
| Download: ML19340A792 (11) | |
See also: IR 05000010/1977004
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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0FFICE OF INSPECTION AND ENFORCEMENT
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REGION III
Report of Operations Inspection
IE Inspection Report No. 050-010/77-04
IE Inspection Report No. 050-237/77-04
IE Inspection Report No, 050-249/77-04
Licensee:
Commonwealth Edison Company
P. O. Box 767
Chicago, IL 60690
Dresden Nuclear Power Station
License No. DPR-2
Units 1, 2, and 3
License No. DPR-19
Morris, IL
License No. DPR-25
Category: C
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Type of Licensee:
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Type of Inspection:
Routine, Unannounced
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Dates of Inspection:
February 14-18, 22, 23, and 28, 1977
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Principal Inspector:
J. S. Creswell
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(Date)
Accompanying Inspectors: Eone
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Other Accompanying Personnel: None
Reviewed By:
itj ef Chiet
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Nuclear Support Section
(Ddte)
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SUMMARY OF FINDINGS
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Inspection Summary
An inspection was conducted on February 14-18, 22, 23 and 20, 1977,
(Unit 1, 77-04), (Unit 2, 77-04),
and (Unit 3, 77-04): Regarding
surveillance of core power distribution limits, determination of
reactor shutdown margin, core thermal power determination, calibra-
tion of LPRM's and APRM calibration. During the inspection two items
of noncompliance were identified regarding conformance with procedures.
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Erforcement Items
Infraction (Unit 2)
Contrary to Technical Specification 6.2.A.5 a detailed written procedure
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was not prepared, approved, and adhered to for calibration of LPRM's
which'had experienced seal failures.
(Paragraph 3, Report Details)
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Deficiency (Unit 2)
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Contrary to Technical Specification 6.2.A.1, Procedure DTS 8232, LPRM
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Calibration, was not adhered to in that the power normalization factor
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was not recorded as required.
(Paragraph 2, Report Details)
Licensee Actian on Previously Identified Enforcement Matters
None inspected.
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Other Significant Findings
A.
Systems and Components
None.
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B.
Facility Items (Plans and Procedures)
.None.
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C.
Managerial Items
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None.
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D.
Deviations
None identified.
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E.
Status of Previously Reported Unresolved Items
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None inspected.
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Management Interview
At the conclusion of the inspection an exit interview was conducted on
February 28, 1977, with Mr. Stephenson and.other members of his staff.
The following items were discussed:
A.
The inspector stated that not performing LPRM calibrations per
detailed written procedures for seal failed LPRM's was an item
of noncompliance.
(Paragraph 3, Report Details)
B.
The inspector reviewed the commitments made in a previous meecing
held February 18 concerning LPRM seal failures. At that time the
licensee had committed to performing IV plots on all LPRM's employ-
ed in Units 2 and.3.
The licensee stated char. this work was com-
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pleted. A commitment was made to perform 7V plots on 15 LPRM's
weekly. The licensee stated that this wort was continuing.
The
licensee asked how long the surveillance on the 15 LPRM's should
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be maintained. The inspector stated that when tSe licensee ascer-
tained that enough data was accumulated to support a conclusion
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that safe operation could be maintained that they should document
their findings by means of a letter to Region III.
The inspector
stated that the information would be reviewed. The licensee had
also committed to develop procedures and criteria for bypassing
LPRM detectors with seal failures. The licensee stated that they
had discussed the seal failure problem with the reactor vendor and
that the vendor had stated that no other phenomenon would produce
a 5% increase in detector output during equilibrium conditions.
The licensee stated they would use this criteria for bypassing the
detectors with seal failures. They further stated that OD-8 com-
puter outputs would be examined daily to monitor the LPRM outputs
during weekdays. During weekends operating personnel will have
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the responsibility for monitoring the LPRM's.
Also discussed was
the criteria for returning the LPRM's with seal failures to ser-
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vice. The licensee stated that they would monitor the output of
the failed LPRM's for stability for a period of time equal'to five
times the interval from failure to stability but not less than 24
hours.
In addition, an IV curve will be obtained for the detector.
to determine that the detector is operating in the " Plateau" region
and no anomalous behavior exists that would prevent the detector
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from functioning in a safe manner. The licensee stated a procc-
dure would be developed to calibrate the detectors prior to return-
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ing them to service. The inspector stated that the calibration
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procedure should include requirements to assure that the calibra-
tion values accurately reflect core conditions at the time of the
calibration. A commitment was also made to document the work
performed in this area. The licensee stated that the procedures
would be in effect by March 31, 1977.
(Paragraph 3, Report Details)
C.
The inspector stated that he had reviewed the methods used for
determining core thermal power. He stated that he had found at
least three different forms which would be used co calculate thermal
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power in the' event of a comput,er outage.
These forms differed
widely'in the degree of accura'cy that could be obtained by their
use.
In some instances, he related, all electrical input to the
recirculation pumps was assumed to be deposited in the reactor
coolant as heat. He stated that this was a non-conservative assump-
tion. The licensee stated that one form would be written which
would use the equations found in the process computer calculation.
It was also found that a constant value for radiation heat loss was
used in'the computer calculation. When he asked the licensee about
data to support the value used he was informed a letter was being
sent to the reactor vendor to ascertain the validity of the number.
The inspector stated that he had reviewed the record of calibration
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of computer inputs for Unit 2 feedwater flow and reactor pressure.
He related that the last record of feedwater flow computer input
calibration was dated March 25, 1975. He also stated he could find.
no record of reactor pressure computer calibration. The licensee
stated that since most of the error in the caloricetric was due to
feedwater flow errors that the feedwater flow computer input calibra-
tion would be _done yearly and that the other inputs would be calibrated.
on a schedule being developed. These items will be reviewed in a
future inspection.
(Paragraph 4, Report Details)
D.
The inspector stated that not recording a power normalization
factor as required by Procedure DTS 8232 was an item of noncom-
pliance.
(Paragraph 2, Report Details)
E.
The inspector stated that he had reviewed the licensee's procedures
for performing calculations in the event of a computer outage. _He
commented on the need for the engineers to be familiar with these
calculations.
He also commented on the need to verify as correct
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the data used as input to the calculations. The licensee stated
that a T bar calculation would be performed on Units 2 and 3, and
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that during these calculations the data would be checked out for
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errors. This item will be reviewed in future inspection.
(Paragraph 5
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Report Details)
F.
The inspector stated he had not found records of APRM gain adjustments
performed af ter LPRM calibrations for Unit 3 on November 19 or
September 8, 1976. The licensee stated that OD-3 had been run and
that the gain adjustment factors had not exceeded 1.02 during the
period mentioned. The inspector noteu that Procedure D:S-700-20,
APRM Gain Adjustment, requires that an' APRM gain adjustment be
performed after LPRM calibrations.. The licensee stated that the
subject procedure was not approved until February 3,1977, and was
not effective on the dates mentioned. The inspector stated this
area would be reviewed in subsequent inspections.
(Paragraph 6,
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Report Details)
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G.
The inspector stated that he had reviewed Procedurs DIS 700-20,
LPRM Amplifier Gain Calibration. He noted that Steg 8 contains no
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criteria for when the nuclear engineers will be notified by the
instrument mechanics concerning the differences between the as-
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found and past current valves.
He stated that such a criteria
should be developed in order to investigate changes that could
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indicated instrument problems. The licensee agreed to develop such
a criteria. This item will be reviewed in a subsequent inspection.
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(Paragraph 7, Report Details)
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REPORT DETAILS
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1.
Persons Contacted
B. Stephenson, Station Superintendent
A. Roberts, Assistant Superintendent
B. Shelton, Administrative Assistant
J. Kolanowski, Unit 3 Lead Engineer
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C. Sargeant, Supervisor of Engineering
J. Dolter, Lead Nuclear Engineer
J. Toscas, Assistant Lead Nuclear Engineer
T. Ravsch, Nuclear Engineer
E. Bussean, Engineering Assistant
J. Wojnarowski, Nuclear Engineer
W. Hildy, Instrument Engineer
A. Zapatocky, Instrument Foreman
R. Thomas, Instrument Foreman
T. Josefik, Operator
2.
Review of LPRM Calibration
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During the review of procedures for LPRM calibration it was found
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that the licensee was operating with over 87 LPRM's with seal
failures. The discussion of seal failures will be undertaken in
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Section 3.
The licensee uses Procedure DTS 8232, LPRM Calibration, to perform
the nuclear operations associated with LPRM calibrations on Units 2
and 3.
Actual instrument gain adjustments will be done by performing
Procedure DIS 700-20, LPRM-Amplifier Cain Calibration.
During the review of Procedure DIS 700-20, it was found no criteria
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existed for the amount of disagreement allowed between as found and
old current valves. Review of this data for a calibration performed
on Unit 3 on November 19, 1976, revealed considerable differences
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between the data.
During the period of time between November 19 to December 2, 1976,
it was found that LPRM 08-49-D was reading approximately four times
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thevaluethattheTIPreadingsingicatedascorrect. On November 19
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theLPRMwasjndicating62.28W/cm with a comparable TIP reading
of 15.37 W/cm
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Review of records associated with Procedure DTS 8232, revealed that
a power normalization factor was not record (d as required. After
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the inspector identified this discrepancy, Deviation Report No.
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D-12-2/3-77-8 was filed by the licensee.
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Review of Procedure DIS 70-20, also revealed that the computer
printout required for the performance of the procedure has not been
modified as required by the procedure. This procedure was approved
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Feburary 3, 1977, and there were no records of calibrations performed
since that date.
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3.
LPRM Seal Failure Investigation
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While examining records of LPRM calibracions the inspector noted
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that some of the detectors had experienced an increase of sensitivity
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of some two to three times their normal value.
The licensee explained
that these LPRM's had undergone the failure of a ceramic seal
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between the chamber volume and the cable volume. The cable pressure,
being about twice that of the chamber pressure, caused an inleakage
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of an Argon / Air mixture into the chamber. The increase in sensitivity
was explained as a result of an increase in number density of gas
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molecules in the chamber.
The licensee was asked how the seal failures were identified and
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what criteria was used for bypassing the detectors. The licensee
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stated that they would notice an increase detector output from
computer outputs and would bypass them until they demonstrated
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stability at which time they would be recalibrated and returned to
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service. The inspector found that: there was no routine surveillance
performed to identify LPRM's with seal failures, there were no
criteria to classify LPRM's as having seal failures, there was no
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written approved procedure for calibrating LPEd's with seal failures,
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and that records of LPRM seal failures were incomplete.
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The method the licensee used to calibrate the LPRM's with seal
failures was as follows:
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a.
A TIP Trace for the instrument thimble associated with the
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failed detector would be obtained.
b.
Readings would be obtained for the operable LPRM's in the
associated string.
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An " eyeball" fit of the TIP trace would be made with the
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operable LPRM readings. The reading for the seal-failed
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detector would be read off the trace for the value indicated
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at that detector's location.
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The LPRM amplifer gain would be adjusted until the LPRM reading
was consistent with the value obtained from the TlP trace.
The inspector reviewed the original and Revision 1 of a Service
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Information Letter (SIL 146). The original letter was dated
August 29, 1975, and was entitled, " Local Power Range Monitor (LPRM)
Non-linearity and Drift."
Revision 1 of the letter was dated January 23,
1976, included additional recommendations.
SIL 146, Revision 1, contains a discussion of the problem which is
given in an abbreviated form below:
a.
Seal failures can produce changes in LPRM readings of up to
250%. The time constant for failure ranges from several hours
to several days.
b.
The failure can produce non-linearity of + 2% full scale due
to gas exchange across the failed seal.
c.
Seal failed LPRM's evidence drift with power distribution
changes.
d.
Saturation voltages increase in LPRM's with seal failures and
this phenomenon may require an increased operating voltage.
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Output may fall up to 4%, for LPRM's experiencing seal failures,
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when a 75% increase in power is experienced. The time con-
stant for the loss in output ranges from 0.1 to ten hours.
An abbreviated discussion fo the GE recommendations are given
below:
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a.
LPRM's with seal failures should be calibrated as soon as
possible after failure to avoid APRM scrams.
b.
IV curves should be obtained for LPRM's with large changes in
sensitivity.
The implementation of the following items is contingent on operation
within 8% of operating limits.
(i.e., MCPR, etc.):
a.
Tolerance (TOL) in RC values for LPRM drift test in P1 calcula-
tion should be no greater than ten.
b.
LPRM's should be calibrated in the 65-85% power range and at
maximum power during recovery and the calibration should be
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checked once per week for two weeks after reaching maximum
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power.
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c.
Following cold startups or changes in control' rod pattern the
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LPRM's should be calibrated at 25%, 50%, 65%, 85%, and maximum
power.
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d.
LPRM's should be calibrated wh never thermal power is changed
more than 15%.
Calibration sh,uld be checked once a week for
two weeks.
e.
Process computer program OD-3 should be demanded every ten
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minutes for the first hour after reaching 40% power and after
any subsequent upward power change greater than 15%. P1
should be monitored every two hours for the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and
every day for the next seven days. The APRM GAF's should be
trended to determine if GAF's greater than 1.0 are occurring.
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APRM's experiencing increased GAF's should be recalibrated.
The letter also contained a sta,tement that the NRC was informed of
the problem. The vendor representative at the site stated that a
letter from the vendor to the Reactor Technical Assistant Branch
was transmitted on September 2, 1975, concerning LPRM's with seal
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failures.
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The inspector met with licensee represenatives concerning the
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recommendations found in SIL 146 to determine whether the licensee
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had implemented any of the recommendations. The licensee stated
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they had not decided to implement any of the recommendations and
showed the inspector a letter that had been sent to the vendor
dated February 9, 1976. The licensee stated in the letter that
they did not intend to implement the recommendations found in SIL
146.
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Based on the concern for safe operatfen with LPRM's with seal
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failures the inspector requested the IV curves be obtained on all
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LPRM's employed in Units 2 and 3,ar4 that. an on-going surveillance
program be established to monitor LPRM performance.
In addition,
he requested that procedures and criteria be developed to identify
LPRM's with seal failures, return LPRM's with seal failures to
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service and to calibrate seal failed LPRM's.
The details of the
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licensee's response are located in the Management Interview section
of this report.
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4.
Review of Core Thermal Power Determination
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Review of the licensee's procedures revealed that core thermal
power for Units 2 and 3 is obtained from the process computer when
it is operational. The inspector reviewgd the process computer
program and found that a value of 2 x 10 BTU /Hr was used as a
constant for radiation heat losses.
The inspector asked to see
the data supporting this value but the licensee could not furnish
him with it.
The inspector reviewed the Unit 2 records for feedwater flow and
reactor pressure computer input calibrations. He found that the
last computer input calibration for feedwater flow instruments 644
A, B, and C was conducted on March 25, 1975. The inspector could
not find a record of computer input calibration for reactor pressure
instrument 647 A.
Procedures were also reviewed which govern core thermal power
determination in the event of a computer outage. The inspector
found the following procedures contained different methods of
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varying accuracy to determine core thermal power:
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DOS 500-6 APRM Gain Adjustment
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DOS 400-1 Nuclear Operating Procedure
DTS 8232
LPRM Calibration
It was found that some of the procedures assume that all of the
electrical engery supplied to the recirculation pumps was deposited
in the reactor coolant system.
5.
Review of Procedures to be Used in the Event of a Computer Outage
The inspector reviewed the following procedures:
DOS 700-5 Critical Heat Fluxs Ratio Analysis (Unit 1)
DTS 8234 Calculation of MCPR (Units 2 and 3)
DTS 8232 LPRM Calibration (Units 2 and 3)
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He found that data used had not been verified nor had sample calcul-
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ations been performed to familiarize the engineers with the procedures.
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6.
APRM Gain Adjustments
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The inspector reviewed Procedure DIS 700-17, APRM Gain Adjustment,
and associated records. Review of the records revealed no document-
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.ation of APRM gain adjustments on November 18 or December 2, 1976,
for Unit 3.
On these dates LPRM gain adjustments were performed.
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7.
LPRM Amplifier Cain Calibration
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The inspector reviewed Procedure DIS 700-20, LPRM-Amplifier Gain
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Calibration. While reviewing Step 8 of the procedure he discovered
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there was no criteria for differences allowed between as found and
past current values. He had noted in the records that seldom did
the two values agree and he was concerned about when the disagreement
reached a certain value whether a problem was indicated that required
analysis.
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8.
LER Review
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The inspector examined corrective actions associated with:
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LER 50-237/1976-67
LER 50-237/1976-69
LER 50-237/1977-1
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Licensee actions in regard to commitments were acceptable.
9.
Shutdown Margin Determination
The inspector reviewed the result of a Shutdown Margin Test performed
on Unit 1 per Procedure DTS 8104, Dresden, Unit 1, Shutdown Margin
Demonstration. No items of noncompliance were identified associated
with this test.
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10.
Rod Block Monitor (Unit 2)
The inspector visited the control room to verify records of LPRM's
presently by passed. While observing indicating lights for LPRM's
in the bypassed condition, the inspector had an operator select rod
F-8.
When rod F-8 was selected, LPRM strings 16-33, 16-25, 24-33
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and 24-25 were also displayed by the rod block monitor (RBM). The
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inspector noted that Detectors A and D in LPRM string 24-33 were
indicated as being bypassed on the front panel but not on the back
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panels. This indicated a possible problem in the RBM circuitry.
The inspector asked the operator how long the problem had existed
and he replied he didn't know. The licensee then initiated Work Request 1525 to check operability of all detector bypass lights
associated with the RBM.
The work associated with the RBM.
The
work was completed on February 23, 1977. The work request states
that Q2 and G4 for Trip Circuits A and B on Card Z28; and Q1, Q2,
and G4 on Card Z27 were replaced.
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