ML20217K380
| ML20217K380 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/30/1998 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20217K359 | List: |
| References | |
| 50-327-98-01, 50-327-98-1, 50-328-98-01, 50-328-98-1, NUDOCS 9804070214 | |
| Download: ML20217K380 (47) | |
See also: IR 05000327/1998001
Text
s. -.
,
.
U. S. NUCLEAR REGULATORY COMMISSION
REGION-II
Docket No.: 50-327.-328
Report No.: 50-327/98-01. 50-328/98-01
L-icensee: TVA
Facility: Sequoyah Nuclear Plant. Units 1&2
. Location: Sequoyan Access Road
Hamilton County TN. 37379
s
Dates: January 26. 1998 through February 13. 1998
Team Leader. C. Smith. P.E. Senior Reactor Inspector
Engineering Branch
Division of Reactor Safety
-
- Inspectors: L. Moore, Reactor Inspector
S. Rohrer. NRC Graduate Fellow
S. Khabir. Mechanical Engineering Consultant
D. Tondi. Electrical Engineering Consultant
Approved by: McKenzie Thomas. Acting Chief
Engineering Branch
Division of Reactor Safety
'9004070214 980330*
^DU"
$" Po! Enclosure 2
, .
,
Executive Si-ery
Sequoyah. Nuclear Plant
NRC Inspection Report.50-327/98-01. 50-328/98-01
.The primary objective of this inspection was to assess the effectiveness of
~
Site Engineering through an in-depth review of calculations, analyses, and
'other engineering documents used to support the Auxiliary Feedwater (AFW)'
system performance during' normal, and accident or abnormal conditions. A
-secondary ~ objective was.to determine the' quality'of 10 CFR 50.59 safety
evaluations performed by the licensee in support of modifications made to the
AFW system.
Doerations
LEmergency and operating procedures were consistent with the AFW system design
'and licensing basis. One exception was noted related to an unverified
assumption for the 10 minute operator action requirement discussed in.the
accident analysis for a Major Rupture of a Main Feedwater Pipe in Final. Safety
Analysis Report (FSAR) chapter.15.4.2.2. This issue was identified as an
unresolvad item pending NRC review of the licensee response documenting their
basis /for assuring the assumption is met or is not required. (Section 03)
Ma1ntenance
The plant material condition and housekeeping observed during the walkdown
indicated that the equipment was being adequately maintained. The detailed
walkdown also verified that the plant configuration was consistent with the
as-built drawings. (Section M2.1)
The post' maintenance test acceptance criteria was consistent with design
. parameters specified in the design and licensing bases. Preventive
maintenance requirements were consistent with the vendor recommendations.
Acceptance criteria in the surveillance tests were consistent with the design
and-licensing bases. (Section M2.2)
._The inspectors identified an Engineering performance strength in root cause
' determination and corrective action for resolution of an industry problem
'related to degraded thrust bearings on centrifugal pumps which resulted in a
symptom referred to as " black oil" (Section M2.3)
Maintenance' history indicated that the system design function had been
- adequately maintained- A violation was identified for failure to perform a
.
- 10 CFR 50.59 safety evalu'ation/ screening when maintenance activity on the 2A-A
LMDAFW pump. rotating element in 1987 and 1996 changed the performance
.
characteristics of the pump as described in;the FSAR, (Section M2.3)
!
.
,
..
,
l
l
2
Encineerina
The inspectors verified that the operational performance capability of the AFW
system was acceptable and the system as installed and operated met both the
original design basis and subsequent licensing commitments as demonstrated by
TS changes 89-03 and 96-07. (Section E1.1)
The inspectors concluded that there was a weakness in the licensee's
justification for the seismic qualification of the vital batteries. An
inspector followup item was identified for this issue. (Section E1.1)
The inspectors determined that the brake horse power (BHP) developed by the
Unit 2 turbine driven AFW pump with motive steam from the steam generators
(121 psig throttle pressure) was adequate to enable the pump to provide 640
gpm flow to all four steam generators. The turbine driven AFW pump was
, demonstrated to be operable for operating modes 1.2.3 and 4. (Section E2.1.6)
The results of the electrical review demonstrated that the motor driven AFW
pump motors were adequately sized. Additionally, these motors were capable of
performing their design function under the most limiting conditions of 153KV
on the 161KV switchyard bus. Adequate circuit protection for the electrical
equipment was also demonstrated along with adequate voltage and current
required for performance of equipment within the AFW system. (Section E2.2.4)
A weakness was identified in the implementation of the design control program
related to the quality of the independent review function for calculations and
technical evaluations. The following examples demonstrated this weakness:
. Calculation SON-CA-0053-0-HCC-LCS-11088. Revision 9. did not evaluate
the effect of vortexing in conjunction with the AFW suction pipe break
during swapover of MDAFW pumps, suction to the ERCW system. This item is
identified as IFI 50-327.328/98-01-03. (Section E2.1.1)
- Calculation SON-03-D53-EPM-GLC-031193. Revision 2. did not consider the
worst case scenario for formation of vortices by using a range of Froude
numbers during condensate storage tank air entraining calculation. This
item was identified as IFI 50-327.328/98-01-04. (Section E2.1.2)
.
Calculation SON-31C-D053-EPM-RG-060987 Revision 1 did not address the
Station Blackout condition of 120 F and did not provide a justification
for reducing the turbine driven AFW pump room direct current exhaust fan
margin. This item was identified as IFI 50-327.328/98-01-05. (Section
E2.1.3)
. Additional examples of weaknesses in implementation of the design
control program were demonstrated by: 1) inconsistent design inputs and
assumptions in AFW calculations (Section E2.1.4) 2) calculation not
.
. .
.
3
including consideration for the effects of. pipe age (Section E2.1.5),
and 3). lack of attention to detail and consistency in design basis
.
documents (Section E3.1)
The licensee's lowering of the minimum voltage requirement for the turbine
driven _ AFW' governor without adequate documentation from the governor vendor-
was a weakness in the design control program. An inspector followup item was
identified for this issue. (Section E2.2.6)
t.
l
. .-
,
.
Reoort Details.
Introduction
The primary objective of this inspection was to assess the effectiveness of
the site engineering 1 organization through'an in-depth review'of calculations.
analyses and other engineering documents used to support Unit 1 Auxiliary
Feedwater (AFW) System performance during normal, abnormal. or accident
conditions. . A secondary objective was to determine the quality of 10 CFR'
50.59 safety evaluations performed by the licensee in support of engineering
modifications made to the AFW ~ system. Regulatory commitments and technical
specification (TS) changes which impacted operation of the AFW system were
also. verified to have been satisfied by the licensee.
The' inspection was performed by a team of inspectors which included a Team
Leader.-one Region II inspector, one mechanical design contractor and one
instrumentation and control contractor. The team was accompanied by a Region
II NRC Graduate Fellow.
I. Doerations
03. Operations Procedures and Documentation
a. Scope
The inspectors reviewed the normal and emergency operating procedures to
determine if the AFW system operation was consistent with the design and
licensing bases.
b. Ob1P%'ations and Findinas
Overall, emergency and operating procedures were consistent with the AFW.
system design and licensing bases. One exception was noted related to
the accident analysis for a Major Rupture of a Main Feedwater Pipe in
the Final Safety Analysis Report (FSAR) Chapter 15.4.2.2. This analysis
listed many assumptions including a ten minute operator action time to
isolate AFW to the effected steam generator. There was no statement or
caution in the procedures which referenced this operator action
assumption. There was no validation or verification that the operator
action could be~ achieved in ten minutes.
A 1995 licensee Problem Evaluation Report (PER) addressed this issue and
referenced simulator training runs of this accident without all the
input assumptions of the analysis, i.e.. a partial power run with main
feed line rupture. These 1995 training. runs demonstrated isolation
times of 9 minutes 54 seconds:and 13 minutes. PER SQ 951623. dated
September 26, 1995, stated that the ten minute action _ statement in the
. Technical Specification (TS) bases could not be achieved with the
- currentE0Psduetotherequirement'for.rigorousadherencetothe
Lprocedures. The resolution was an evaluation by engineering which
~
, -concluded that the 10 minute operator action assumption referenced in
,
__
, .
,
.
2
the TS bases and the FSAR was not a requirement and recommended a
corrective action to delete the statement from the TS bases.
The inspectors concluded that the applicability of the FSAR assumption
was not adequately resolved. That is, given that the licensee had
identified that operators may not be able to complete this task within
the tine frame assumed in the FSAR analysis, there was no licensing or
procedural actions taken to assure that the assumption could be met or
was not required. The concern was with RCS heatup without an available
heat sink. The analysis assumed 10 minutes with no feed flow since all
flow was assumed to go out the break. After 10 minutes, 1070 gpm AFW
flow to the steam generators was assumed. The question is, if this AFW
flow were to be delayed greater than 10 minutes, would the RCS
temperature and pressure exceed safety limits or the pressure for ECCS
injection? Although the licensee stated that the simulator run in 1995
was not an attempt to validate the 10 minute assumption of the accident
analysis, the results provided a question regarding the licensee's
capability to meet the FSAR analysis assumption for the main feedwater
piping rupture accident which was not adequately resolved. This item is
identified as unresolved item URI 50-327,328/98-01-02, FSAR Chapter
15.4.2.2 Accident Analysis Assumption fnr 10 Minute Operator Actions to
Isolate AFW From the Affected Steam Generator on a Main Feed Line
Rupture not Verified or Validated. The inspectors requested that the
licensee provide a written response to the NRC for this item. This item
is unresolved pending NRC review of the licensee's evaluation and
documentation of their basis for assuring the assumption is met or is
not required.
c. Conclusion
Emergency and operating procedures were consistent with the AFW system
design and licensing basis. One exception was noted related to an
uriverified assumption fer operator action in the accident analysis for a
Major Rupture of a Main Feedwater Pipe in Final Safety Analysis Report
(FSAR) chapter 15.4.2.2. This issue was identified as an unresolved
item pending NRC review of the licensee's documentation of their basis
for assuring the assumption is met or is not required.
'
,
l
J
. .
,
4
i
II. Maintenance
M2 Maintenance and Material Condition of Facilities and Equipment
M2.1 Material Condition Walkdom
a. Scope
The inspectors performed general field walkdowns to assess the material
condition of the AFW system. A detailed walkdown was performed of the
Unit 1 AFW piping from the turbine driven AFW (TDAFWP) pump suction side
to the steam generator number three containment penetration. The field
configuration, including seismic supports, was verified against the as-
built drawings. The verified field configuration was used to verify the
accuracy of the system flow model (EZFLOW).
b. Observations and Findinas
The general material condition of the AFW equipment was good.
Housekeeping in the equipment areas was good. Piping and equipment were
painted with few indications of corrosion, oil leaks or water leaks.
The following documents the inspectors' observations from the
detailed walkdown.
Verification of EZFLOW Model to as built Plant Confiouration
The EZFLOW model in Calculation SON-03-D53-EPM-WLL-063094 was compared
to sections of isometric design drawings that had been verified during
walkdowns. All of the valves, pumps, elbows, reducers, and increasers
were accounted for. The pipe schedules and materials were correct and
the lengths used were accurate with some conservatism. One exception
was noted one link was about 8.5 feet too short and its neighboring
link was about 8.5 feet too lorig. This discrepancy would not affect the
results of calculations performed with the model, but an item was added
to 50980016PER to correct the error in order to be more accurate. 3
i
It was also verified that 1096 psig was input as the inlet pressure for I
EZFLOW nodes corresponding to the four steam generator inlets. I
i
Reouired 00erator Actions l
Operator actions which must be performed in the west valve vault 1
(opening and controlling air operated level control valves) would have i
to be performed when the area could be at about 160-170 degrees l
Fahrenheit ( F). This would be a harsh environment for operator action, i
even for a few minutes. Further it was acknowledged by the licensee
that communications must be maintained during the operation with the
. .
,
.
4
control room and perhaps an operator in the TDAFW pump room. A portable
radio systems would be used to communicate. The licensee.had not
demonstrated that the quality of communication between the control. room
and pump room needed to support level control valve (LCV) manual
operation (for 30 minutes) would be acceptable during an accident or SB0
condition.
ERCW Pioina Corrosion
Condensate storage tank (CST) and essential raw cooling water (ERCW)
piping systems were inspected and found to be adequate. However. the
inspectors noted that transition pieces between the ERCW double
isolation valves to each AFWP are drained to avoid cross contamination
from the ERCW to the CST water system. This arrangement also allows
exercising the ERCW valves for opening / closing in accordance with the
Generic Letter (GL) 89-10 motor operated valve (MOV) program
requirements. This is accomplished by leaving the tell-tale drain
valves open, allowing continuous exposure of the ERCW transition pipe's
and valves internal surfaces to the outside environment. The corrosion
rate increases the with presence of oxygen. Filled system corrosion 1
effect is less due to a lack of oxygen. The inspectors requested the
licensee to provide data for measuring corrosion rate for exposed
transition pieces which ensured that the ERCW piping minimum wall
thickness was maintained. Based on the information provided. the
inspectors had no further concerns.
c. Conclusion
The plant material condition and housekeeping observed during the
walkdown indicated that the equipment was being adequately maintained.
The detailed walkdown also verified that the plant configuration was
consistent with the as-built drawings.
M2.2 Maintenance and Surveillance Procedures
a. Scope
The inspectors reviewed maintenance and surveillance procedures to
determine if acceptance criteria were consistent with the design and
licensing bases,
b. Observations. Findinas and Conclusion
The inspectors reviewed the procedures listed in the appendix to this
report and reviewed a sample.of completed surveillance tests. The post
maintenance test acceptance criteria specified in the maintenance
procedures was consistent with the design parameters specified in the
t I
..
{
.- .
,
.
-5
design and licensing bases. Preventive maintenance requirements were
consistent with the' equipment vendor recommendations. Acceptance
criteria-in the surveillance tests were consistent with the design and -
licensing bases.
.M2.3 Maintenance History
-a. Scope
The inspectors reviewed the maintenance history of AFW equipment to
determine'if performance of corrective maintenance was consistent with
the design and licensing bases.
b. Observations and Findinas
The. inspectors identified an Engineering performance strength in root
cause' determination and corrective action for resolution of an industry
problem related to degraded thrust bearings on centrifugal pumps which
resulted in a symptom referred to as " black oil". The degraded bearings
resulted'in increased pump vibration, maintenance, and subsequent
equipment out of service time. The resolution included a' change in
bearing material which was accomplished on one pump and was scheduled
.for.the remaining pumps.
The inspectors identified two examples in which maintenance activities I
introduced equipment design changes that were not consistent with the
licensing basis. Specifically, changes were made to the 2A-A motor
driven AFW (MDAFW) pump rotating element during 1987 and 1996
maintenance activities which changed the flow characteristics and power
requirements of the pump. ~There was no 10 CFR 50.59 screening or
evaluation performed to address whether these changes could be
accomplished under the provisions of 10 CFR 50.59. ,
I
.On October 13, 1987, work request WR B232398 replaced the rotating
element of the 2A-A MDAFWP. Subsequent post maintenance testing
identified that the pump discharge pressure at 30 gpm (1660 psi) i
exceeded the design pressure.of the piping (1650 psig). On October 29.
1987. PER S0P 871598 was initiated for engineering to analyze the
.
operability of this issue. The evaluation determined the condition was
acceptable but did not include a 50.59 evaluation to determine if this
- new' design was consistent with the licensing bases as described in the
FSAR. Unit 2 was restarted from an extended shutdown in May, 1988.' PER
. SOP 871598 was-closed-on September 7. 1990. Additional technical
1
evaluationsfand.a 50.59 screening evaluation were performed in 1990'as
part of the restart review process. The PER had been identified as a-
1
t
N
I
1
t
. .
.
'
,
6'
post-restart' item. The technical evaluations included statements which
demonstrated that component performance characteristics were changed.
- 1.e.:
1. 100 pounds per square inch (psi) increase in shutoff head of
pump
'2. Flow contribution to the faulted steam generator would
increase less than 10 gpm_( now 2175 gpm calculated versus
2286 gpm analysis limi.t)
3 .' Power required was 540 hp
The 50.59 screening-(page 29 of 55) responded "NO" to the question.
"Does the proposed activity affect (directly or indirectly) any
' information presented in the SAR or deviate from the description given
in the SAR: by changing the system or design functional requirements or
by changing the' text, tables, graphs, or figures."
Although the impact was.not significant and did not challenge system
operability, it did impact SAR tables and graphs. Table 10.4.7-2 lists
- the system design pressure as 1650 psig and design head of 2900 feet at
440 gpm. Also. composite pump curves, figures 10.4.7-7 and 10.4.7-6
were impacted. Additionally, the 50.59 was performed 3 years after the
maintenance activity was accomplished.
On October 19. 1996. WO 96-038636 increased the impeller / casing wear
ring clearance _to resolve excess thrust conditions which were resulting
in increased vibration and maintenance on the 2A-A MDAFW pump. The-
clearance was increased to .021 inches in accordance with a maintenance
instruction that had been revised to permit the increased clearance
allowance beyond nominal. This value was provided by a 1990 vendor
manual change that was incorporated into the vendor manual in 1993.
There was not a 50.59 screening evaluation for the maintenance
instruction or vendor manual changes.
On October 29, 1996. PER 962756 was initiated to address that the 2A-A
pump casing dimensions were unacceptable and corrective actions were
initiated to procure a new pump from Watts Bar.for replacement of the
entire pump. ;The; casing out of tolerance conditions were identified
during the maintenance which changed the impeller clearance (WO 96-
038636, dated October' 19.1996). _The PER. stated that the out of
- tolere'ce condition caused difficulty in reassembling the pump. The PER
.- stated as a corrective action to " develop a "use-as-is" disposition for
the existing pump . casing to allow the 2A-A pump to be returned to
'
-
service."
,
I
-
,
. .
,
.
7
~
On November 1.' 1996. PER SQ 962788PER Rev.1. identified that the
maintenance activity which increased the_ pump impeller clearance
_
invalidated portions of two nuclear calculations (auxiliary power _ system
and EDG' load calculation). The PER stated the task should have been
performed under the. design control program. The Level B PER was
-initiated by the site quality organization. The licensee's MRC review
was performed November 18. 1996. The PER corrective action included an
engineering evaluation of the change which assessed system operability
but did not require a 50.59 evaluation.
This engineering evaluation for this PER stated the following pump
conditions that were inconsistent with the licensing bases as described
in the FSAR:
1. The new impeller and old impeller do not share the same pump
curve although the shapes are similar.
2. The new pump impeller would drive the full system flow
upwards on the system resistance curve.
3. The additional flow from the stronger new impeller will
require additional hp at the maximum power requirement at
447 gpm for a total of 555 hp. (Note: The FSAR EDG load
table listed the load at 544 hp).
Although the above evaluation indicated the performance characteristics
of the pump were changed by this maintenance activity, no 50.59
screening / evaluation was performed. A technical evaluation. dated
November 11. 1996, in this PER concluded that the configuration was
acceptable for continued operation. The extensiveness review performed
by Watts Bar on this PER stated the impeller clearance change task
should have been done by design change notice (DCN) because the pump
horsepower changed which could impact EDG ampacity, and breaker
'loadset. It further stated that the DCN process would have caused the
50.59 to be performed. Approximately one year later, on November 1.
1997. MDAFW pump 2A-A was replaced with a pump procured from Watts Bar
and modified to meet the Sequoyah MDAFW pump curves.
'Although the 50.59 screening / evaluations were not performed for these
two maintenance activities' that implemented changes to the performance
characteristics of safety related components, the licensee performed
operability; evaluations which determined that the equipment and system ;
would be. operable under.the. system conditions. Emergency diesel !
l generator loading margins were adequate.to the absorb calculated change
sin power. requirements for the pump. These technical evaluations
tincluded a' safety assessment which verified the operability of the
9 l system before the pumps were returned to service. The inspectors
,
- *
o
.d__
8
concluded that these' maintenance activities. involved changes which
established conditions which were not consistent with the licensing
bases as described in the FSAR and, therefore, required a .10_ CFR 50.59
screening / evaluation (which was'not performed). .This is identified as -
Violation 50-328/98-01-01, Failure to Perform 10 CFR-50.59 Evaluations-
for Changes Implemented Under Maintenance to Motor Driven AFW Pump 2A-A.
c. Conclusion
Maintenance history indicated that the system design function has been
. adequately maintained. A strength was identified for engineering
. performance in root cause determination and. resolution in resolving an
industry problem related to degraded bearings (black oil condition) in
centrifugal pumps.
A violation was identified for failure.to perform a 10 CFR 50.59 safety
evaluation / screening when maintenance activity on the 2A-A MDAFW pump
rotating element _in 1987 and 1996 changed the performance
characteristics.of the pump as described in the licensing bases.
III. Enaineerina
El. Conduct of Enaineerina
El.1 Conformance with Reaulatorv/Licensino Commitments
a. Scone of Review
The' inspectors verified that regulatory commitments involving design
changes which impacted operation of the AFW system had been completed
for the following TS changes:
. TS 96-07, Revise as found setpoint tolerance band for the
Main Steam Code Safety Relief Valves from +/- 1% to +/- 3%.
. TS 89-03, Implement requirements for logic time delays
associated with automatic transfer of AFW pumps suction.
The inspectors also evaluated the adequacy of the documentations which
demonstrated that the 125 Volts Vital DC System had seismically
qualified batteries.
.
. .
,
.
9
b .- Observations and Findinas
--TS Chance-96-07. Revise as found setooint tolerance band for MSSV
TVA,-in a letter dated August 28. 1996 (TVA-SON-TS-96-07), requested.a
revision'to TS Sections 3.4.2 3.4.3, and. Table 3.7-2 to' relax the
setpoint tolerance for the pressurizer safety valves.(PSVs) and the main
steam safety relief valves (MSSVs). TVA stated that based on industry
and SONP experience the +/ 1% tolerance was not sufficient to
accommodate. valve setpoint- drift over one entire fuel cycle. . The
American National Standards Institute /American Society of Mechanical
Engineers OM-1, recognized +/- 3% as an acceptable criteria and TVA .
wished to take advantage of this industry supported relaxation.
In a. letter to TVA dated September 29, 1997, the NRC transmitted
Amendment Number 229 to facility operating license number DPR-77 and
Amendment Number 220 to facility operating license number DPR-79 for
Units ~1 and 2 respectively. The amendments consisted of changes to the
TS in response to TVA's application dated August 28, 1996, as
supplemented by letters dated March 17. March 27. April 3, and July 15,
1997. The amendments revised the as found setpoint tolerance band for
the pressurizer code safety relief valves and the main steam code safety
relief valves from +/- 1% to +/- 3%. .The Safety Evaluation prepared by
the office of Nuclear Reactor Regulation for amendments number 229 and
220 found these changes to be acceptable.
The inspectors concluded that increasing the MSSV setpoint tolerance to
+/- 3% would result in increasing the secondary system operating
pressure and create additional pressure head-for the AFW pumps in the
steam generators. Design basis calculation SON-01-D053 0-HCC-ML-072586.
MSSVs' Set Pressure Verification, Revision 2, was reviewed by the
inspectors and demonstrated that the licensee had evaluated the design
change which increased the setpoint tolerance band from +/- 1% to +/-
3%. :The calculation coricluded that the verified MSSVs design data
justified the design requirements provided in (1) Design Criteria for
Main' Steam System, SON-DC-V-4.1.1 Revision 7, and (2) Contract No.
71C57-92696.. Specification 1270 for SG Safety Valves for Sequoyah
Nuclear Plant Units 1 and 2 when the valves set tolerances were a
maximum of ' +/- 3% .
. Design basis calculation SON-03-D53-EPM-WLL-063094. AFW Hydraulic
Analysis. Revision'1, was prepared by the licensee in order to develop a
.
base hydraulic'model of the AFW system from the condensate storage tanks
to the steam generators for Units 1 and 2.using EZFLOW. hydraulic
analysis' software. The inspectors reviewed Appendix F of.this
5
? calculation which had been prepared.to determine the maximum steam
generator pressure that the AFW system would have-to pump against, This-
..
.. .
,
.
10
appendix identified the main steam line. break and loss of normal
feedwater as the most demanding heat up transients with respect to AFW
flow requirements. The decay heat removal needed to mitigate these
events bounded the AFW flow requirements. In order to ensure that the
AFW system can meet these flow requirements the maximum credible steam
generator pressures seen during these events were determined with a
MSSVs setpoint tolerance of + 3%. This calculation demonstrated that
the maximum steam generator pressure requiring bounding AFW flow was
1096 psig.
The inspectors next reviewed design basi.s calculation 2219280000.
Minimum Head Required For the Turbine Driven and Motor driven AFW Pumps.
Revision 11. in order to evaluate the analysis performed by the licensee
to demonstrate the capability of the AFW pumps to provide design flow
against a pressure _ head of 1096 psig. This calculation determined the
minimum required total dynamic head (TDH) that the AFW pumps must
develop to assure that the pumps can deliver the minimum required design
basis flow. Revision 11 of this calculation used the EZFLOW OA
hydraulic software to model the AFW system the base model of which was
contained in calculation SON-03-D53-EPM-WLL-063094. This calculation
concluded that the AFW pumps capability to meet design basis flow
requirements (minimum required flow) was assured if the pumps could
develop differential ~ pressures equal to or above the values tabulated in
the results section at recirculation flow conditions or at the design
basis flow conditions. The inspectors determined that the most
stringent demands were identified for motor driven pump 2B-B. This pump
had a minimum required TDH of 1228 psig at required flow condition of
440 GPM and 1486 psig at required recirculation condition of 30 GPM.
Acceptance criteria fer testing the AFW pumps were listed on drawing
number 1, 2-47W803-3 Revision 13. The inspectors observed that the
values listed on the drawing were more conservative than those listed in
the calculation ar; were based on a previous revision of the
calculation. No deficiencies were identified during review of the above
calculations.
TS Chance 89-03. Automatic Transfer of AFW Pumo Suction Loaic Time
Delavs
The licensee, in a letter dated May 25. 1989, requested amendment to the
TS to revise tables 3.3-3. Engineered Safety Feature Actuation System
Instrumentation; 3.3-4. Engineered Safety Feature Actuation System
Instrumentation Trip Setpoints; and 4.3-2. Engineered Safety Feature
Actuation System Instrumentation Surveillance Requirements. The
proposed changes would add requirements for logic time delays associated
with the motor driven and turbine driven AFW pumps automatic suction
transfer.. This application fulfilled TVA's commitment to have the time
.
.
11
delay values for the time delay circuitry in the switchover logic for
the AFW pumps included in the TS.
The NRC staff, in a letter dated November 28, 1989, approved TS
amendments number 129 and 116 for operating licenses DPR-77 and DPR-79
respectively. The inspectors reviewed the following design basis
documents and evaluated the capability of the system to perform its
design function as described in the Safety Evaluation Report prepared by
the NRC staff:
. Calculation SON-CA-D053-0-HCG-LCS-110882. AFW Pressure
Switch Setpoints. Revision 9
. Design Criteria Document No. SON-DC-V.13.9.8. Sequoyah
Nuclear Plant-Auxiliary Feedwater. Revision 8
. Drawing CCD No.1-45W646-6. Wiring Diagrams Feedwater Pump &
Turbines Schematic diagrams. Revision 12
. Drawing CCD No. 1. 2-45N657-5. Wiring Diagrams Separation
and Miscellaneous Auxiliary Relays Schematic Diagrams,
Shaet 5. Revision 15
- Drawing CCD No.1. 2-47W803-2. Flow Diagram Auxiliary
Feedwater. Revision 51
Based on the above reviews the inspectors determined that on low suction
pressure a 2 out of 3 delayed logic signal opens the train "A" safety
grade ERCW supply valves to the turbine driven AFW pump. The logic was
generated by pressure switches PS-3-121A. B and D with a time delay of
5.5 seconds. If the low suction pressure signal has not cleared in an
additional 5.5 seconds the logic initiates a signal to close train "A"
FCV 3-136A and 136B and open train "B" FCV-179A and 179B in order to
provide safety grade ERCW to the turbine driven AFW pump. Additionally,
upon low suction pressure a 2 out of 3 logic signal was generated by
pressure switches PS 3-139A. 139B. and 1390 for motor driven AFW pump
1A-A: and by pressure switches PS 3-144A. 144B. and 144D for motor
driven AFW pump 1B-B. Automatic switchover of ERCW isolation valves FCV
3-116A and B (train A) and FVC 126A and B (train B) was verified to
occur within a time delay of 4 seconds for the motor driven AFW pumps.
The logic and time delays implemented by the design basis documents
fully implemented the licensee's commitment and was consistent with the
description contained in the Safety Evaluation Report prepared by the
NRC staff.
_ - _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _
. .
,
.
12
The inspectors' review of calculation SON-CA-D053-0-HCG-LCS-110882
identified a concern related to vortexing during a pipe break in the AFW
suction line from the condensate storage tank line. The specific
concern involved failure of the calculation to consider air entrainment
during a line break upstream of the AFW pump suction piping. Air
entrainment by the motor driven AFW pumps could result in degradation of
- their operation and is discussed further in Section E2.1.1 of this
inspection report.
Batterv Seismic Oualification
The FSAR stated that the battery racks and vital batteries will meet
seismic category I requirements. The inspectors asked if the licensee
had documentation in the file which demonstrated that the batteries
themselves were seismically qualified. The licensee produCPJ a
certificate of compliance from the battery manufacturer C&G Power
Systems Safety Related LCUN-33 (cell) batteries. The certificate of
compliance qualification was based on qualification by equivalence to
other tested batteries and analyzed battery racks of the same design.
(Ref. C&D Qualification Report No. OR-24269-01). Qualification by
equivalency has been acceptable to the NRC. However, the inspectors
were not able to identify the criteria considered by the vendor to
support the argument that equivalency had been attained. For example,
no specific reference, i.e.. no other nuclear plant which was licensed
with these same batteries was referenced. Nor have specific C&D aged '
and non-aged cells been identified fully equivalent to the LCUN-33 cells
throughout the Wylie test program.
The inspectors questioned whether the licensee *s certificate of
compliance alone was adequate to verify qualification. This was the ]
position taken by TVA during discussions concerning this issue. The NRC 1
'
will review further the purchase specification and the Wylie file to
verify the validity of the seismic test conclusions on the C&D LCUN-33
cell report. Inspector followup item 50-327.328/98-01-07. Review Wylie
Laboratory Battery Seismic Qualification Test Report.
c. Conclusion
The inspectors concluded that the licensee nad implemented design
changes which fully satisfied their regulatory commitments for TS
changes 96-07 and 89-03. Approved design basis documents accurately
reflected the as built plant configuration. An inspector followup item
was identified to verify the validity of the seismic test conclusions.
1
)
- .
..
.S.
13
E2 ~Endineerina Sunoort of Facilities and Eauioment
. E2.1> Mechanical Desian Review
-The inspectors reviewed the design basis calculations for the AFW system
which~ included review of AFW system Thermal-Hydraulic, piping stress,
and equipment sizing calculations.
E2.1.1 Calculation of Auxiliar_v Feedwater System Pressure' Switch Analytical
Limits SON-CA-D053-0-HCG-LCS-110882 Rev: 9
a. Insoection Scone
The AFW system pressure switch analytical limits calculation was
reviewed; This calculation is used to establish the analytical limits
for the pressure switches and associated time delays that control the
automatic transfer from the condensate storage tank to the safety grade
Essential. Raw Cooling Water supply. The lower analytict ~ .imits
determined by the calculation are required to limit vori.u formation in
the CST and prevent air entrainment into the suction lines. The
inspection was performed to evaluate the adequacy of the calculation
assumptions and design input parameters.
b' ' Observations and Findinas
' Assumptions were supported and they were conservative. The calculation
was revised to include additional considerations involving the worst
case scenario to calculate the Net Positive Suction Head Available
(NPSHA). The scenario considered an auxiliary feedwater suction piping-
guillotine break at the auxiliary and turbine building boundary after a
seismic event. The calculation concluded that adequate NPSHA existed
during.the scenario. It also established adequate duration for the ERCW
injection valve to flow and protect the pumps.
During the course of this review, the inspectors concluded .that the
methodology used for calculating the swapover time delay was inadequate
.(calculation must consider the most efficient cross section i.e. , wetted
perimeter to calculate the out-flow through the break as in an open
channel flow) and did not support its conclusion. The inspectors'
independent calculation determined that during the time delay of seven
seconds, cavitation could occur due to vortexing. Since both Units 1
and 2 AFW pumps share the same suction piping, the vortexing may result i
in degradation of both unitsE pump performance during the ' pipe-break
scenario. .Sequoyah: Units;1 and 2 AFW pumps'may experience ingesting air
due to'_ formation of vortices-in the suction piping. The calculation did
4 4
'not' address- the AFW pumps suction piping submergence requirement.to
avoid vortexing .in conjunction with a pipe break.
-'
_4' t
.--
)
, .
.
14
c. Conclusion
The inspectors' review concluded that, although the calculation proved
that there was adequate NPSHA, the calculation did not evaluate
operability of the AFW system in conjunction with assuming a pipe break
due to formation of vortices in the AFWPs suction piping. This was
considered as an example of inadequate implementation of the design
control program and is identified as Inspection Follow-up Item (IFI) 50-
327,328/98-01-03. Formation of Vortices in AFW Pumps Suction Piping.
E2.1.2 Calculation of Condensate Storaae Tank (CST) Usable Volume for
Auxiliary Feedwater Use SON-03-D53-EPM-GLC-031193 Rev. 2 dated 1-24-98
a. Insoection Scoce
The CST usable volume for AFW use was reviewed. The calculation was
used to verify the usable volume of water in the CST for AFW. The
calculation considered the potential for vortexing and determined the
minimum level above the AFW pump suction piping to prevent air
entrainment. The calculation also determined the amount of water used
by AFW to remove decay heat after a reactor trip (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Hot Standby
condition), for a 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Station Blackout (SBO) condition. and for a
bounding worst case Main Feedwater Line Break (MFLB)/ Main Steam Line
Break (MSLB) event. The inspection was performed to evaluate the
adequacy of the calculation assumptions and design input parameters.
b. Observations and Findinas
The calculation assumptions were adequate and used sound engineering
approach. However, assumption two did not support the worst case
scenario associated with formation of vortexing. This assumption cited
NUREG-0897 as the basis for using a Froude number of 0.4. There was no
basis to use this Froude number to calculate the CST discharge piping
minimum submergence value. NUREG-0897, Revision 1 identified typical
envelope analysis curves for air ingestion, surface vortex activity, and
swirl in-PWR sumps with dual pump vertical intakes and references
figures 3.37, 3.38, and 3.39. The NUREG also stated that there was no
reliable indicators (void fraction, pressure loss coefficient, and swirl
angle) to predict formation of vortex. However, measured levels of air
ingestion, even with air core vortices, were generally less than 2%.
For submergence of 8 feet or more, none of the configuration tested
indicated air-drawing. vortices ingesting more that 1% over the entire
flow range, even with severe flow perturbation.
The calculation used a Froude number of 0.4 to determine the submergence
height without identifying the vortex type, even though the enveloping
l range of Froude number of >0.2 to >1.0 could be chosen (depending on j
l
!
l
u ;
-
, ,
,
4
15
varicus vortex types). The inspectors identified the significance of
0.4 to the usable volume of 190,000 gallons. An independent calculation
was also performed by the inspectors to establish the worst- case
scenario required to calculate the usable volume for the CST. The
result of this independent calculation identified the submergence of 3
inches with a Froude number of 2.5 for the vortex type of 5 (vortex
pulling air bubbles to intake). This new submergence height equates to
an additional 3.100 gallons which will not be usable as part of 190,000
gallons required per the technical specification.
Additionally, the inspectors' independent calculation determined that
any other Froude number less than 0.4 by the licensee would have volume
than the CST volume of 190,000 gallons, which would have negated the
minimum TS value.
c. Conclusion
The inspectors concluded that although the original intent of the
calculation was met, the calculation failed to consider the worst-case
scenario for formation of vortices by using a range of Froude numbers.
This item is identified as IFI 50-327,328/98-01-04, Nonconservative
Froude number used in vortex analysis.
E2.1.3 Calculation of HVAC Eauioment Reauirements Evaluation: TDAFW Pumo Room
SON-31C-D053-EPM-RG-060987 Rev. 1
a. Insoection Scooe
The HVAC equipment requirements evaluation for the turbine driven
auxiliary feedwater (TDAFW) pump room was reviewed. The calculation was
used to verify the design requirements of normal LOCA with/without loss
of offsite power conditions of the plant. Additionally, the calculation
established the maximum design temperature. cooling loads and available
and required flow in cubic feet per minute (CFM) for the TDAFW pump room
for LOCA. The inspection was performed to evaluate the adequacy of the
cniculation assumptions and design input parameters.
b. Observations and Findinas
The calculation assumptions were adequate and used sound engineering
apnroach. However the inspectors observed the following deficiencies:
1. As stated in the new revision, the TDAFW pump room DC exhaust fan,
as credited for during SBO. operates at a reduced CFM compared to
the original revision of the calculation that established the
' design CFM. The margin was reduced from 32% to 10%. This
reduction in the margin was determined to be acceptable by the
. .
,
-i
']
16
licensee. engineering staff. This deficiency had been identified
by the licensee and corrective' action was being pursued via PER
No. SONPER0137.
~ 2. . The. calculation'did not address events.such as SBO The upper
temperature of 120*F associated with the equipment qualification
as' intended by the objective of this calculation' was not used-for-
qualification of the TDAFWP room DC exhaust fan.
'3. The calculation specified a fan' design flow rate of 1,200 CFM,
which corresponded to the value shown on the flow diagram Heating
& Ventilation Air Flow 1,2-47W866-2 Rev.10. There was no basis
'for this design flow rate. During the course of the inspection.
the; inspectors discovered that the design flow rate of 1,580 CFM
previously documented in FSAR Section 9.4.2.2.7. Revision 0, was
removed in Revision 1 of the FSAR dated January 4,1989.
c. Conclusion
The inspectors concluded that the calculation did not address the SB0
condition temperature of 120 F. Additionally, the calculation did not
provide' acceptable justification for reduction in the margin for the
TDAFW pump room DC exhaust fan. Also, the calculation did not meet its
intent by' addressing the equipment qualification requirements for the
TDAFW DC exhaust fan. The licensee had issued PER SONPER0137 to address
the inspectors' concern. This item was considered a weakness in
implementation of.the 10 CFR 50 Appendix B design control program and is
identified as IFI 50-327.328/98-01-05. TDAFW Pump Room DC Exhaust Fan
E0.
E2.1.4 Calculation of Recuired Stroke for Auxiliary Feedwater Motor Driven
Pump LCVs SON-CA-0053-EPM-JVM-050289 Rev. 6
a. Insoection Scoce
The required stroke time for MDAFW pump injection valves was reviewed.
-The calculation was used to justify continued unit operation _ if the
stroke' time values associated with the MDAFW pump injection valves to
steam generators failed to meet the required opening within 60 seconds.
.b. Observations and Findinas
The. inspection was performed to evaluate the adequacy of the calculation
assumptions and. design input parameters. The calculation assumptions
lwere. adequate and'used sound engineering approach. The following
, ,
' documents the inspectors' observations.
4
t m.
. .
,
.
I
17
1. Inconsistency in design input parameters - Pressure drops across
venturis were not consistent with other calculations such as SON-
03-053-EPM-WLL-063094 Rev. 1. AFW Hydraulic analysis. Appendix G
of this calculation identifies the pressure drop of 60 psid at 440
gpm, across the venturi downstream of pump 1B-B, compared to 102
psid at 440 gpm as used in SON-CA-0053-EPM-JVM-050289 Rev. 6.
Similarly, the inconsistency exist for pump 28-B (67.77 psid vs.
62 psid).
2. Inconsistency in design input parameters - The calculation
identified the minimum total developed head for AFW pumps that
were inconsistent with the calculation 2219280000, and Flow
Diagram 1,2-47W803-2, 3 Table A-3, Minimum Head Required For the
AFW oumo This Calc.(ft/osid) 2219280000(osid)
1A-A 2893/1252 1229
1B-B 2940/1273 1223
2A-A 2890/1251 1206
28-B 2920/1264 1228
c. Conclusion
The inspectors concluded that these deficiencies did not impact the
overall operability of the AFW system but indicated a weakness in the
implementation of the licensee's design control program.
E2.1.5 Calculation AFW System Recirc. Line Final Orifice. SON-03-D053-EPM-
VIK-040391 Rev. 6
a .. Insoection scooe
The calculation of AFW system recirculation line final orifice sizing
was reviewed. The calculation was used to determine the final design
differential pressure for sizing the single stage orifices located in
the new recirculation lines for each AFW motor driven-pump. The
inspection was performed to evaluate the adequacy of the calculation's
assumptions and design input parameters.
b. Observations and Findinas
The calculation assumptions section identified a relative roughness for
all piping of 0.0018. The calculation Section 4. design margins or
safety factors., stated that additional friction loss had been considered
for old pipe. This was consistent with industry practice. However,
additional consideration for pipe aging had not been used consistently
at'Sequoyah. Friction loss in pipe is sensitive to changes in diameter
i
~1
.. .
,
.
18
and roughness of pipe. In many services. the. interior of' pipe becomes
encrusted with scale, dirt. tubercles or other foreign matter: thus,_
industry has typically made allowances for expected diameter changes.
For a given rate of flow and a fixed friction ~ factor, the pressure' drop
per foot of pipe varies inversely with the fifth power of the diameter.
A 2% reduction of diameter causes a 11% increase in pressure drop; a 5%
reduction of diameter increase pressure drop 29%. -
-c. Conclusion
The inspectors' review concluded that, although the AFW system was
designed and installed correctly there was a deficiency in applying
industry practice i.e.. effect cf pipe aging. This was considered a
weakness in implementing the licensee's design control' program.
-E2.1.6 Calculation AFWPT Steam Suoolv Line Desian Adecuacy. SON-01-0053-0-
HCG-ML-080586 Rev. 4
a. Insoection SCoDe
The calculation of TDAFW pump steam supply line design adequacy was
reviewed. The calculation was used to determine the steam flow rates to
satisfy the required TDAFW pump performance for various modes of
operation. i .e. . Modes 1.2.3. and 4 per TS 3.7.1.2. The inspection was
performed to evaluate the adequacy of the assumptions and design input
parameters.
b. Observations and Findinas q
The inspection revealed that the assumptions were adequate and used
sound engineering approach. The inspector determined that the TDAFW .
pump available brake horsepower (BHP) at the minimum load was 79 BHP
(2.6%) which was marginal when compared to the required BHP of 77 per
the manufacturer recommendation (Ref. 6. 8). Based on the results.f o
pre-operational test data however, the licensee demonstrated that this
margin was actually 11%. The inspectors concluded that conservatism in
the calculation accounted for the difference in margin.
The TDAFW pump 2A-s had a pre-operational test performance at the low
lsteam generator endpoint of 125 psig (Pre-Op Test TVA-22 Section 5.4.3.
dated 4-24-80). The test used motive steam from the steam generators
.(121 psig throttle pressure) to supply the AFW turbine. The pump
supplied at least 130 gpm to each steam generator (640 gpm actual flow).
Based on the collected-data and using conservative 55% pump efficiency.,
the available BHP is 85.6 (11% margin). The inspectors' review
concluded that the 11% BHP margin was acceptable and considered this ';
item'as.not.affecting the equipment operability.
-
'
'
.
,
1
. .
,
-
}
19
.
.c. . Conclusion .
The inspectors' review concluded that the TDAFW pump was operable in
. Modes 1, 2. 3 and 4. The design calculation verified the Terry Turbine
operability for various loads at the required brake horsepower (BHP).
E2.1.7 Calculation of Analysis to Sucoort Chanaina TDAFW LCV's Actuator and
Sizina Criteria of the Air Cylinder. SON-03-D053-EPM-NOL-021993.
Rev. 2
a. Insoection Scoce
The analysis to support changing TDAFW Level Control Valve's (LCV)
actuator. and sizing criteria of the air cylinder was reviewed. The
purpose of this calculation was to determine the size of TDAFW LCV's
actuator.and the adequacy of the air cylinder to provide each LCV at
least 4 full strokes during the 4-hr station blackout (SBO). The
inspection was performed to evaluate the adequacy of the calculation
assumptions and design input parameters,
b. Observations and Findinas
The calculation assumptions section identified that this calculation
contains' no unverified assumptions. However, the inspectors identified
a discrepancy in the LCV's spring rating used in the calculation. The
.Masoneilan pneumatic spring diaphragm actuator number 18 had a spring
rating of 1100 lb/in. with the allowable load of 3300 lb. Revision 2 of
the calculation used 1100 lb/in. for the actuator thrust force for
closure and 2200 lb/in, for opening of the LCVs. The calculation
Revision 1 used the spring rating of 2200 lb/in. for both opening and.
closing of the valve.
Another inconsistency identified by the inspectors was in calculating
the response time on fail open LCV. Because Revision 2 of this
calculation used two different spring rates, it failed to make
subsequent. changes in the response time of the LCVs. The response times
of 3.45 seconds for a fail open LCV could have been changed to 7.12
seconds if the correct spring rate of 1100 lbs/in. was used. However,
the change in the response time would not have had any impact on the
system operability because: 1) the valve operating time was less than or
equal ~to 60. seconds to' perform its safety function per SON-DC-V-13.9.8.
Land 2) there was no operator action outside the Main Control Room (MCR)
required to manually open the TDAFW LCVs during the first 60 minutes of
a SB0 per SB0 per. SON-03-D053-EPM-NQL-021993. Rev. 2.
.
i
. _ _ _ _ _ _ - -
. .
,
.
i
20 I
c. Conclusion
The inspectors' review concluded that operation of the LCVs would not be
affected by these inconsistencies and deficiencies. As stated above.
the response time for the actuator spring to open the valve (fail open)
7.12 seconds did not affect the operation of the AFW and the valve.
These deficiencies have been categorized as the licensee's lack of
attention to details, and therefore. a weakness in the design control
program.
I
E2.1.8 Mechanical Modifications
a. Insoection Scooe
The inspectors reviewed several mechanical modification packages in
order to evaluate the licensee's effectiveness in implementing NRC
requirements and licensee design control program commitments.
b. Observations and Findinns
The inspectors reviewed DCN M06185B. The purpose of this DCN was to
eliminate low flow pulsation problems that had resulted in excessive
j maintenance and decreased reliability. The modification resulted in
! increasing the recirculation flow from 25 gpm to 165 gpm by up-sizing
L the existing recirculation orifices from 25 to 30 gpm by installing a 2-
inch.135-gpm recirculation line parallel to the existing recirculation
line. The inspectors' review determined that the design change package
was acceptable and met the requirements of General Design Criteria GDC-4
of 10 CFR 50. Although this modification eliminated the immediate
pulsation problem at low-flow conditions. it has resulted in the
installation of additional hardware and administrative controls for
, operation of the system from the control room. The new flow control ,
'
valves (FCV) FCV-3-400 and FCV-3-401 fail closed upon loss of control 4
air or loss of electrical power. Anticipated Transient Without Scram
(ATWS) Mitigation System Actuating Circuitry (AMSAC), and LOCA. In
reviewing the modification supporting document, the inspectors verified
that the proposed change in the logic for FCV-3-400 and FCV-3-401, as
shown on drawing 1.2-47W611-3-3. Mechanical Logic Diagram Auxiliary
Feedwater System. Rev. 22, was adequately implemented in the electrical #
schematics shown on drawing CCD No. 1,2-45N603-6. Rev. 1.
c. Conclusion
The inspectors concluded that the modified flow control valves were
designed and installed properly. The 10 CFR 50.59 safety evaluation
performed for this plant modification was considered acceptable.
._. __
. .
,
(:.
21
E2.1.9 Administrative Control of Condensate Storaae Tank Level
a. Insoection Scone
' The inspectors reviewed documents related.to the CST supply for the AFW
system. -The documentation was checked for consistency between the
design and licensing basis and for the implementation of design
information into' plant procedures. '
b. Observations and Findinas-
' Detailed Design Criteria 3.7.2.3, AFWP Water Supply, required that a -l
minimum'of 190.000 gallons of water in each CST be reserved for the AFW,
including an allowance for water not usable because of vortexing or tank !
discharge line location. The associated TS required as a condition of
operability that'it be verified every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that the volume of water
in the CST is at least 190,000 gallons when it is the supply source for
the AFW system. The TS did not require that this volume be useable.
The inspectors reviewed the operating procedure which included the TS j
L verification, serving as an administrative control over the CST level.
The instruments referred to in the procedure had been scaled to read in
gallons. The scaling document identified a static head correction based
on the location of the transmitters.18 inches above the bottom of the
tank, but it did not take into account the fact that the tank discharge
-
line was three inches above the bottom of the tank. This resulted in
2.746.88 gallons (about 1.5 percent of the TS requirement) of unusable
wate'r being included in the instrument output.
<
This finding was ' discussed with licensee personnel and'the following
(' facts were cited.
1. The TS associated with the 190.000 gallon CST. volume did not
require .that the volume be usable.
2. The CST.is not safety related.
3. There is a low level indicator at an elevation of 721 feet. Make-
up water flow is -initiated by this signal and is switched off upon
receiving a high level. indication from an instrument at an
-
' elevation of 736 feet.
Calculation SON 03 053 EPM-GLC-031193, Revision 2 demonstrated that the
minimum height required to_ maintain 190.000 gallons of water above the
AFW inlet was:721 feet and,1 1nch. The low level signal is received
~
when only 188.966 gallons of water are available to the-AFW System.
,
.. 6
'--
- . _ ___ _.
. .
,
4
22
c. Conclusion
The inspectors concluded that the detailed design criteria was
conservative when compared to the TS requirement regarding CST level.
Additionally, the operating procedures were sufficient to meet the TS
requirement. but were not consistent with the detailed design criteria.
These findings have no safety significance but are indicative of a
weakness in implementation of the design control program. Additional
information on the CST useable volume is discussed in Section E2.1.2
(IFI 50-327.328/98-01-04) of this inspection report.
E2.2 Electrical Desian Review
E2.2.1 Calculation SON-CA-D053-0 HCG-LCS-082983. AFW System Cavitatina Venturi
Motor Driven Pumo HP Reauirement
a. Insoection Scone
The inspectors performed a review of design bases calculations, vendor
pump and motor performance curves. and performed independent
calculations in order to determine the maximum BHP rating of the AFW
pump motor based on specified process system demands. The following
documents the results of these reviews.
b. Observations and Findinas
AFW Pumo Motor Maximum BHP Ratina
Design basis calculation SON-CA-0053-0-HCG-LCS-082983. AFW System
Cavitating Venturi Motor Driven Pump HP Requirements. Revision 5. was
revised to determine the worst case horse power requirements for the
motor driven AFW pump. Design input information in this calculation
specified a motor brake horse power (BHP) rating of 540 BHP. with a flow
of 650 gallons per minute (GPM) at the venturi and 30 GPM recirculation
flow. This calculation concluded that the worst case horse power
requirement for the motor driven AFW pumps was 544 HP.
The inspectors reviewed the following vendor documents and performed
independent calculations in order to verify the pump shaft BHP
requirements for the process demands specified in the calculation:
. Ingersol Rand Curve No. C08741408. dated July 15. 1997.
. Ingersol Dresser Pump Co. Order 073-62227. Speed Torque
Curve, dated February 9. 1998.
.
.
23
. Allis Chalmers Manufacturing Co. Order No. B-5112-90194-1,
Report of Test for Induction Motor.
. Allis Chalmers 500 HP. 6600 V. 3 Phase, 60 cycle, 3600 RPM,
Motor Speed-Torque Curve.
Based on the above reviews the inspectors determined that the pump was
capable of providing a flow of 680 GPM with a total dynamic head (TDH)
of 2100 feet. The inspectors calculated the pump shaft BHP with an
efficiency of 70 percent at these conditions to be 540 HP.
The Allis-Chalmers motor nameplate information for the installed motors
showed a rated horse power of 500 HP with a service factor of 1.15. The
inspectors concluded that the maximum continuous rating of the installed
motors was 575 HP which had a 5.69% margin in comparison to the 544 HP
documented in the calculation referenced above.
The inspectors reviewed the pe <jeed-torque curves and performed an
independent calculation in order to determine the motor BHP requirements
at a design flow of 465 GPM with a TDH of 2900 feet. The results of
this calculation demonstrated that a motor rating of 487 BHP was
required for these process system demands. This value of motor BHP
rating was bounded by the 544 bhp documented in the referenced
calculation.
A plot of the pump speed-torque curve was made on the speed-torque curve
for the motor. Review of this plot revealed that with a rated motor
terminal voltage of 6600 Volts seventy five percent of full load torque
was available for accelerating the load upon starting the motor. The
plot also revealed that the motors were adequately sized to perform
their design function of providing a design flow of 465 GPM to the steam
generators during a design basis accident (DBA).
c. Conclusion
.
The inspectors concluded that the motor driven AFW pump motor was
adequately sized based on: 1) a process system demand of 465 GPM with a
TDH of 2900 feet and 2) 650 GPM at the venturi with a recirculation flow
of 30 GPM.
i E2-.2.2 Auxiliarv Power System Imorovements
a. Insoection Scoo.e
The inspectors reviewed modifications implemented by TVA during the
1990's in order to identify and assess the impact of the modifications
on the plant electrical system.
. .
.
24
b. Observations and Findinas
In discussions with TVA electrical engineering personnel, the inspectors
were informed of several recent plant electrical system improvements
which were installed at Sequoyah (SON). These improvements implemented
during the 1990's should significantly improve the quality reliability,
capability. and the availability of both the onsite and offsite power
system which support the AFW system, as well as other safety systems.
No attempt was made during this inspection.to quantify the positive
impact of the electrical system improvements. The inspectors concluded
that the following major improvements should result in improved safety-
margins (both AC and DC voltage) in the electrical distribution system.
TVA has added capacitor banks in the switchyard. TVA has modified their
offsite power to supply engineered safety feature systems directly from
the CSST transformers, thus eliminating the need for a less reliable
fast automatic transfer (on unit trip) from the unit auxiliary
transformers to the CSSTs. In addition. TVA has included automatic
transformer tap changer capability to ensure maintaining desired voltage
levels to support safety systems from the 6900 Volt level through the
lower voltage bus levels. In addition to the above modification. TVA
also improved the capability of the onsite Class IE System by replacing
their 125 Volt DC vital batteries. A 250 Volt DC balance of plant
battery located in the turbine building was also replaced. During the
last day onsite, the inspectors were informed that a new diesel driven
fire water pump was installed to replace the electric motor driven fire
pump that was loaded on the AC emergency power bus,
c. Conclusion
The inspectors concluded that, as a result of the above mentioned plant
electrical distribution system upgrades, the capability and the capacity
of the SON power system was significantly improved and provided a more
reliable power source than it had in the past to support the AFW system
safety functions in all modes of operations including station blackout.
The recently installed vital batteries support. (enhance) the 120 Volt AC
boards (inverter source) as well as providing the 125 Volt DC
requirements for the AFW system components during the SBO.
E2.2.3 FSAR Table Load Correction
a, 'Insoection Scoce.
.The inspectors reviewed FSAR Section 8.3 to verify that the information
in the applicable tables was consi. stent.
L,
L
. .
,
.
25
b. Observations and Findinas
During the review of FSAR Section 8.3-1, the tables for EDG loading and
for load shedding were reviewed. The inspectors noted that the rating
values (HP) for the AFW pump motor were different in each table. In
each case, the HP value was conservative from a safety perspective. The
licensee agreed to correct the FSAR Tables 8.3-1 and 8.3-2 for
consistency. The licensee prepared a FSAR change request during the
inspection to resolve this inconsistency.
c. Conclusion
The inspectors concluded that the different HP values for the AFW pump
motor in FSAR Section were conservative from a safety perspective.
E2.2.4 Calculation 50N-EEB-MS-T106-0002. Auxiliary Power System Analysis.
Revision 37
a. Insoection Scooe
An independent evaluation of the capability of the AFW pump motor to
perform its design function under the most limiting condition of
degraded voltage on the 161 KV switchyard grid was performed.
b. Observations and Findinos
The above calculation documented TVA's evaluation of the plant AC
auxiliary power distribution system (6.9KV and 480V) for the following
conditions defined in FSAR Sections 8.2 and 8.3 and Design Criteria SON-
DC-V-114.1.
. Normal Operation
. Safety Injection Phase A (SI-A) accident signal
. Safety Injection Phase B (SI-B) accident signal
The calculation modeled Units 1 and 2 steady state case (all conditions)
and Units 1 and 2 motor starting voltages at 0 and 5 seconds for unit
station service transformer (USST) connected; and 0,2,3.4.5 and 6
seconds for common station service transformer (CSST) connected. In the
models considered. the other unit was in full load rejection for all
cases.
All starting motors were evaluated at an offsite power supply voltage of
153 KV which was a bounding minimum preferred power supply voltage based
on transmission' system studies performed by the Transmission Planning
Systems. Loads that were required to be started automatically upon
occurrence of a DBA were evaluated to ensure that the load terminal
. .
,
4
26
voltage was adequate to support equipment performance. The 161 KV grid
was assumed to drop instantaneously to 153 KV in conjunction with the
. block starting of all safety.'related loads actuated by the safety
1.njection SI phase A or B signal. The 6.9 KV shutdown board (SDB).
voltage would also' drop below the degraded voltage setpoint of 6456
volts.to approximately 5850 volts. After a time delay of two seconds,
the. automatic load tap changers (LTC) on the CSST would start boosting
the voltage approximately 1.25% per second until the voltage recovered
to within the LTC voltage range of 6997 to 710'/ volts. The degraded
voltage relay would be reset at 6595 volts-within six seconds of the
- voltage recovery.
The inspectors reviewed the calculation in order to verify that
acceptance _ criteria for transient voltage performance were met by the
AFW pump motors. The ' acceptance criteria specified were:
. The 6.9 KV SDB voltages recover to 6600 volts within 10
seconds after a transient below 6456 volts to allow
resetting of the second level under voltage relay.
. Medium voltage Class 1E motors receive adequate starting
voltage at t=0 and are accelerated to full speed within 5
seconds.
Sheet No. 250A. "AFW Pump Motor Evaluation". from the calculation
identified 6.9KV shutdown board 2A-A as having the worst case voltage
evaluation with a board voltage of 5858.7 volts at the start of the
transient, i.e., at t=0 seconds. This analysis was described as
bounding for AFW pump motors 1A-A.1B-B. and 28-B and was used as design
.
input information by the inspectors for independent calculations to
verify the capability of the AFW pump motors to perform their design
'
function.
Based on review of attachments 10.4.6. 10.4.8. 10.4.10. 10.4.12.
10.4.14. and 10.4.16 of the calculation, the inspectors verified that
6.9 KV shutdown board 2A-A had satisfied the acceptance criteria for
voltage transients below 6456 volts. The 6.9 KV shutdown board 2A-A
voltage profile for safety injection-phase B actuation showed that the
bus: voltage recovered to 6900 volts within 10 seconds after initiation
of the. transient. - Using a value of 6233 volts which represented the
-vol tage~on-the 6.9 KV. shutdown board at t=4 seconds =into the transient
'
., the inspectors independently calculated AFW pump motor 2A-A motor
_ terminal voltage to be 94 14% of~ nominal voltage. Additional
calculations using the motor speed torque curves demonstrated that the
motor developed .98% of the full load torque with this value of terminal
voltage' and was capable of accelerating the pump up to slip speed and
provide a design flow of 465 gpm. A calculation of the motor starting
.
..
.- -
.
27
torque with a bus voltage of 5858.7 volts at t=0 was also performed.
The results of this calculation-demonstrated that the motor had a
terminal. voltage of 88.48% nominal voltage'and developed 89% of full
' load torque.. The inspectors concluded that the AFW pump motors would be
r . capable of accelerating the pump which required 15% rated full load
torque at starting.
The inspectors reviewed calculation SON-E3-002. Diesel Generator Load
Analysis Revision 32, and strip chart recordings of EDG voltage for.
surveillance test 2-SI-0PS-082-026A, which was performed April 22, 1996.
The surveillance test demonstrated that the EDG voltage dropped to a
minimum of 5958 14 volts upon' starting the 2A-A AFW pump motor. This
value bounded the value of 5858.7' volts at t=0 when powered from the
auxiliary electrical distribution' system. The inspectors. concluded that
calculation SON-EEB-MS-T106-0002 was the bounding calculation which
demonstrated that the AFW pump motors were capable of performing their
design function under the most limiting condition of 153 KV existing on
the 161KV switchyard bus.
c. Conclusion
The inspectors concluded that the AFW pump motors would perform their
design function of accelerating the pumps up to the rated speed of 3560 ,
revolutions per minute and provide rated flow of 465 GPM to the steam
generators with a degraded grid voltage of 153KV.
E2.2.5 Load Manaaement Durina SB0 to Assure Voltaae Adecuacy
a. Insoection Scooe
The inspectors reviewed the load management (load shedding) program
developed to ensure adequacy of battery capacity and voltage levels to
support required loads daring a SB0 event.
..
b. Observation and Findinas
i During the team review of the Class Iti electrical system, both AC and
'
DC. the licensee provided .information regarding their requirement for
electrical load. management. i..e., the need for load shedding and the
avoidance' of inadvertently applying loads which may be supplied from
emergency buses- -The most significant load management activity was
.
i thatc at the:end of a 4. hour SB0 period, the vital batteries maintain a
minimum voltage sufficient-'to ensure operation of all 120 Volt AC and
'
125 Volt DC safety components required and to ensure operation of the
p AFW system DC valve motors.. solenoids, TDAFW pump speed controls. TDAFW
L
"
system ventilation fan motor, etc. Upon reviewing several voltage drop
- calculations and vendor specified minimum terminal voltage requirements,
u
...
. .
,
28
the inspectors found that those items evaluated were capable of
performing their required safety functions, even during the worst case
scenario, a postulated 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> station blackout. The inspectors noted
the requirement that, within 45 minutes of the initiation of SB0 the
designated loads (listed) are to be stripped from the batteries. If
this were to be successfully accomplished by operator action, the
battery minimum terminal voltage would be at or above 105.32 Volts DC
(SON-CPS-057. Table C.3) This worst case voltage calculation was
performed with the battery assumed to be at end of life (80% rated
ampacity) and with the battery at its lowest permissible TS temperature
(60 F). In addition, the loss of a single cell (59 versus 60) was
assumed and a zero design margin. The actual battery design margin of
27.25 amperes would increase the value of the terminal voltage (2.65
Volts) to 108 Volts at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, i.e., end of the SB0 event. The
inspectors concluded that, based on the adequacy of successful load
management within the 45 minutes, the battery terminal voltage would be
adequate to support its safety loads.
The worst case component terminal voltages for AFW system components was
discussed with the licensee's electrical staff to understand their'
evaluation and calculation process. The control power voltage drop
circuit calculations were performed during the SON restart program (mid-
to late-1980's). The calculations were based on a sampling technique j
and did not evaluate every circuit, but as a whole were intended to i
justify every circuit. Since that time, any new design work had a {
prepared a detailed voltage drop calculation to support its design
change. Since any given AFW system component may ')r may not have been
analyzed. TVA addressed the inspectors' questions concerning voltage
adequacy by using as an example. a severe AFW system circuit, which was
from SON-VD-Volts DC-1. Appendix 11. "TDAFWP Control Circuit Analysis."
The worst case voltage drop and main concern in Appendix 11 was for the )
FCV-1-51 (TDAFW Control Valve). The calculated voltage drop from the !
battery board to the MOV was 28.76 volts, which resulted in a calculated
voltage at the terminal of 81.39 volts. The minimum voltage specified
by the vendor was 70 percent or 80.5 volts. This appeared to be very
little margin,'however. TVA's calculation used a locked rotor current
value of 14 amperes. This locked rotor value was expected to last only
a few milliseconds because the torque required to open the valve was
accomplished by a hammer-blow. The valve was stated to require two
ft/lbs of force to unseat and rated torque current for this valve would
be a maximum of 6.3 amperes, less than half of the locked rotor current.
This would increase the calculated voltage at the MOV terminal to about
94.15. which was a significant margin over the 80.5 Volts DC specified
by the vendor.
i
i
i
-
. .
,
-
,
29
.c. -Conclusion
The inspectors concluded that. based on the adequacy of successful
implementation of, load management within 45 minutes, the vital batteries
. terminal voltage would support their safety loads.
E2.2.6 Terry Turbine Governor Voltaae Reauirement
i
.a'. Insoection Scoce
The inspectors reviewed the Terry Turbine governor voltage requirements
in order to determine minimum operating terminal voltage for the TDAFW
pump Woodward governor,
b. -Observations and Findinas
.TVA. produced a memo from Terry Turbine, the vendor who supplied the
turbine for the TDAFW system. The memo supported the licensee's
position that the required minimum terminal voltage of 100 volts at the
terminals of the Woodward governor was acceptable. The inspectors
questioned whether the licensee should have contacted Woodward Governor
. Company (who supplied the governor to Terry Turbine) and not the turbine
supplier, to verify that the minimum of 105 volts DC, as specified by
Woodward. could be lowered to 100 volts. TVA's position was that they
purchased the turbine from Terry Turbine and the memo orovided by Terry
Turbine was considered by TVA to be adequate. The inspectors stated,
however, that the manufacturer of the component (in this case., Woodward
Governor) should provide their specifications regarding minimum / maximum
operational-limits. The memo from Terry Turbine did provide adequate
justification to support the conclusion that the Woodward governor would
operate at the lower value of 100 volts. This issue will be followed up
.by the NRC to determine.whether the governor manufacturer, Woodward, was
in agreement with the information provided by the Terry Turbine
supplier. This issue will be identified as IFI 50-327.328/98-01-06.
Terry Turbine Governor Minimum Voltage Requirements.
c. Conclusion-
~
iThe inspectors concluded.that the licensee's lowering of the minimum
voltage requirement for the turbine driven AFW governor without adequate
-documentation from the governor vendor was a weakness in the design
-
. control process'. An inspector followup item'was identified for this
-issue.
,
j
- _
-
- h k; -
'
,
L 9
. .
,
.
30
E2.2.7 Auxiliarv Feedwater System Comoonent Cable Amoacity
a. ~Insoection Scooe
The inspectors reviewed the results and assumptions used in the AFW
system component cable ampacity calculations in order to determine the
~a dequacy of the calculations.
b. Observations and Findinas
The electrical cables required for the AFW components were addressed in
cable ampacity studies. These studies were based upon the voltage level
being applied to the cables. The calculations documented the studies
and results for 120 volts AC: 125 volts DC: 480 volts AC level cables
routed in trays: and 480 volts AC and 6900 volts AC in conduit. The
cable ampacity sampling program concluded that only a small percentage
-of 120 volts AC and 125 volts DC cables could produce sufficient heat to
warrant an ampacity analysis. For example, the AFW system solenoid
valves and control circuits do not carry sufficient current (much less
than 1 amperes) to warrant an ampacity analysis.
Calculations SON-EPS-007 and SON-CSS-002 evaluated 480 volt AC MOVs and
concluded that all_MOVs were acceptable with respect to ampacity. Since
MOVs were intermittent loads .they were not usually energized for a long
enough duration to produce appreciable heat in the cables.
Calculation SON-EPS-008 evaluated the cable ampacity of the 6900 volt AC
cable in conduit which included the load cables for the MDAFW system
pumps. The Units 1 and 2 AFW system pump motor cables were specifically
evaluated and found to be acceptable. The inspectors noted that the
cable was 2/0 AWG and carried a full load current of 40 amperes (43
amperes at 544 BHP). The ampacity calculation sheets for the MDAFW
system pump motor show an allowed ampacity of 70.91 Amperes after
imposing appropriate derating factors,
c. Conclusion
Based on the above licensee assumptions for components and calculations I
!
for the AFW system pump motors, the inspectors concluded that the
,
ampacities for the AFW system equipment were acceptable.
I
i
l
!
. .
31
E2.2.8 Fuse Sizina and Coordination for 120 Volts AC and 125 Volts DC
_ Circuits
a. Insoection Scoce
The inspectors reviewed the licensee's methodology used in fuse sizing
and coordination by walking through a sample circuit in order to
determine the acceptability of the methodology.
b. Observations and Findinas
The inspectors selected a circuit at random and along with the
licensee's engineering personnel evaluated the calculations which had
been prepared for fuse sizing and coordination of 120 volts AC and 125
volts DC circuits. Electrical calculation SON-CPS-051 evaluated all the
safety-related system 250 control circuits for: 1) selective
coordination 2) verification that continuous loading on protective
devices was less than 80 percent of device nominal rating. 3) cable
protection, and 4) that the maximum available fault current was within
the interrupting capacity of the devices. The scope included all
circuit protective devices, both fuses and circuit breakers, that were
installed in the circuits. Calculation SON-CPS-013 analyzed the 120
volts AC and 125 volts DC circuits for selective coordination for
cascaded fuses. Calculation SON-CPS-003 sized the fuses for 100 and 150
Volt amperes control power transformers. Calculation SON-EEB-MS-TIO6-
0008 evaluated inrush requirements for fuses in control power circuits
fed from individual control power transformers during a degraded
voltage. The overview presentation of the TVA program appeared
comprehensive.
The inspectors selected LCV-3-125 and performed a review of design
output documents associated with this equipment. The design output
documents'were DWG 45N603-2 (Wiring Diagram / Schematic Diagram). the 125
Volt Vital Battery Board III DWG 2-45N703-3. the SON-CPS-051 Battery
Continuous Loading Evaluation (page 9 of 16). the SON-CPS-051
calculation showing the circuit breaker and fuse coordination
relationship, and several other pages that comprised the Equipment
Management System and TVA documentation process. Based upon the review
of data 3 resented by the licensee, it appeared that the issue of fuse
and breater sizing and coordination had been given significant attention
by the licensee in response to the NRC's past concerns and the degraded
voltage issue,
c. Conclusion
The inspectors concluded that the licensee methodology for electrical
protection circuit analysis was acceptable.
. .
,
.
32
E2.2.9 Auxiliary Feedwater System Comoonent Voltaae
a. Insoection Scooe
The inspectors reviewed the AFW system component voltage in order to
verify that'the licensee had identified minimum terminal voltage for AFW
system components that would be greater than that specified by the
vendors to ensure adequate equipment operation,
b. Observations and Findinas
The inspectors requested and received from the lead electrical engineer
a two page printout listing all electrical components that were a part
of the AFW system. The two page listing identified each unique item.
its power source. the calculation number where the voltage drop
calculations resided, the voltage available at the components terminal.
and the components' minimum required voltage to function based on
information from component manufacturers. Based on review of this
listing the inspector concluded that the licensee had determined the
required minimum voltage available to all components that were a part of
the AFW system.
c. Conclusion
The inspector concluded that listed components would experience
acceptable terminal voltages for postulated accidents and for the
station blackout event.
E2.2.10 Station Blackout Electrical Eauioment Room Temoerature
a. Insoection Scoce
The inspectors reviewed the results of ventilation requirements to
ensure that AFW components and electrical supporting systems would
remain operable during a SB0 event and would not become inoperable due
to excessive temperatures.
b. Observations and Findinas
TVA had conducted an analysis to verify that equipment required to
maintain the station during the postulated 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 event would remain
operable, and that at the end of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> period, the required
During the inspection. the inspectors
~
equipment would be operable.
verified that the vital inverters each had cooling fans (actually four
per inverter) internally powered from the AC output. The inverters were
the only available source of AC power during the postulated SB0 event.
The inspectors concluded that the inverters would be adequately cooled. i
l
. .
.
33
The inspectors also investigated another area ventilation concern when
it was learned that the calculation of the air flow provided by the DC
motor driven fan required for cooling the TDAFW pump room during a SB0
was (by test) delivering less than calculated air flow. In addition. it
was not clear in the original calculation that, the fan motor was
assumed to be operating at the degraded voltage level of the vital
batteries when nearing the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 duration.
These calculations (SON-31C-D053. Revision 0: SON-31C-D053. Revision 1:
and EPM-RG-060987) were prepared to verify that the air flow rates i
required for the TDAFW pump room ventilation system met the cooling
loads in the calculation EPM-DLM01-03-997 to ensure room temperature did
not exceed 110 F. The DC fan flow rate (margin) was reduced (from 32%
to 10%) following testing but was deemed to remain adequate for most
events. i.e.. normal operation and LOCA with and without a loss of off
site power. Room temperatures for these events appeared to be
acceptable, however. for the SB0 event. this may not be the case. The
SB0 for SON was assumed to last for four hours. During that time the
voltage o,ailable to the fan motor would be dropping. This aspect of
the adequacy of DC fan cooling the TDAFW pump room and maintaining the
temperature below 110 F during a SB0 was currently being reviewed by
TVA. This issue is discussed further in Section E2.1.3 of this report.
Based on the review of SB0 Heat Load Calculation SON-SOS 2-0077 Revision
2 - Computer Program Used: MITAS II. (TMG) the inspectors determined
that the Thermal Model Generator (TMG) Code met all OA requirements and
was used in essential and safety related calculations. The TMG Code
superseded the old computer code MITAS II. The calculated curves
(computer generated) showed that the temperature transients during a
four hour SB0 condition for the auxiliary building elevation 749 .
remained below 89 degree Fahrenheit (elevation 749 - 480 volts Board
Rooms: 125 volts Vital Battery Rooms: 5th Vital Battery Room; and the
Mechanical Equipment Room. One exception was noted for the 480 volts
Board Room 1B where temperatures rose to 96 F after four hours. No
calculations were included in the document with computer generated
curve.
c. Conclusion
The inspectors concluded that the 480 volts Board Rooms and the 125
volts Vital Battery Rooms would not over heat during a SB0 resulting in
failure of. equipment and components relied on to cope with SB0 and to
restore the plant when power would be restored.
- 4
L _
. ..
,
L .
34
E2'.3 Instrumentation & Control (I&C) Review
a. Insoection Scooe
The 1nspectors reviewed instrument loop-accuracy calculations 'for
.several of the instrumentation and controls elements of the AFW system.
in_. order to verify their capability to perform their safety function.
The inspectors referred.to the FSAR. applicable TS, and the AFW Design
Criteria Document.
b. Observations and Findinas
AFW Instrument Process / Safety Limits
-The inspectors reviewed the AFW Instrument Process / Safety Limits
calculation (SON-CA-D053-0-HCG-LCS-032384) Revision 17. dated
January 22, 1998. -The calculation determined process / safety limits for- i
instruments utilized for control loops associated with the TDAFW and the1
MDAFW pumps, level control valves primary steam supply' switch over, and
steam supply isolation and level transmitters'. The' licensee stated that
'the process safety limits calculated would ensure that adequate
feedwater flow was provided to the steam generator. This calculation
was revised based upon the licerisees self assessment of the AFW system.
In all, over twenty temperature, pressure, and level instrument loops
were analyzed by this calculation to verify process / safety limits
efficacy.
Temoerature Switches
.The temperature switches TS-1-17A and 17B and TS-1-18A and 18B provide
signals to FCV-1-17 and FCV-1-18 respectively, to isolate the TDAFW pump
steam. -The isolation signal performs a safety function to protect other
safety related equipment in auxiliary building from a harsh environment
in the event of a steam line break.
The temperature switches must function to isolate the TDAFW break but
they also must not. fail so as to inadvertently isolate the steam line.
The licensee stated process / safety limits for the switches are
summarized below: -
- Maximum limit < 210 F
Minimum limit >110 F
.Thest limits appeared to be. acceptable and the temperature switches
would perform their safety function because the TDAFW room temperature
was calculated to not exceed 110 0F. However, in the SB0 scenario, the
licensee has adopted NUMARC 8700 which would allow SB0 environment
._.
Y
J
- *
. ,
.
35
ambient. temperatures of 120 F in the auxiliary building. The
inspectors did not consider this to be a safety issue. However, if the
. licensee should ever adopt NUMARC recommendation of 120"F this would
conflict with the value of 110 F documented in the calculation of record
referred to above.
Instrument Accuracy Calculation
The inspectors reviewed demonstrated accuracy calculation (1,-TS-1-17A.
B: 1, 2-TS-1-18A. B) Rev. 7'for the subject temperature switches
The primary temperature elements were located in a harsh environment at
the time required to perform a safety function. The temperature.
switches are required for post accident monitoring. Design Criteri_a
Document SON-DC-V.13.9.8. Table 1 note 1. stated that process limits do
not include instrument inaccuracy, drift, seismic effects, etc. and
specified process limits of 110 to 212 F for an increasing parameter to
insure TDAFW pump steam supply was isolated for a steam break in the
TDAFW pump room. This calculation was revised on January 23.1998 in
order to incorporate a methodology that was based on a TVA Branch
Technical Instruction EEB-T1-28 (Ref. 6) in the calculation. The set
point for the-switch was 148 F and response time was stated as 15
seconds (design input data). The accuracy calculation (worst case) was
determined to be acceptable. The calculation'for the high side was
169.8 F (safety limit 210 F). The inspectors concluded that the
licensee's method and calculations were acceptable.
Pressure Switches
Pressure switch PS-3-138A provided a signal to FCV-1-15 and FCV-1-16 for
steam line switchover to.the alternate steam supply source (SG#4) if the
primary source (SG#1) was not available. _This automatic switch over was
considered a backup to manual capability provided the operator. The
upper process / safety limit was based on the minimum required SG pressure
- in order for the TDAFW pump to operate.~ The minimum in calculation
(Reference 4.12) was stated to be 110 psig, however, the pressure at the
switches must be greater to account for frictional loss and difference
in elevation in order for the AFW to discharge into the SGs at 110 psig.
Friction' losses at low flows were neglected. The upper process / safety
limit was determined by adding the delta from the difference in
elevation between the TDAFW pump discharge and the entrance to the SG.
The upper maximum process safety limit for the switch was calculated to
be 140 psig. The minimum process / safety limit was equal to the
difference in elevation between the steam generators and the TDAFW pump
discharge (30 psig).
1
The time duration in the accident analysis for steam supply switch over
was 10 minutes. The switchover would only be required in the event of a
'
, m.
, .
..
a .
E ,.
36
.mainifeedwater line break or a main steam line break and a loss.of
- offsite~ power. The TDAFW would attempt to start. -The time delay logic
~
. would begin timing out and many other. actions _would occur. The bottom
line indicates a maximum time delay process / safety limit of;480 seconds.
- A minimum-process / safety. limit-was. based on,the turbine. reaching. full
speed.in 20 seconds'and is required in order for the logic-to function
- as designed.
~ Pressure' switches PS-3-148'-156. -164, and -171 allow switch over from
' the 4.' inch MDAFW pump SGs level control valves (LCV-3-148. -156A. -164A
and 171A to the 2 inch bypass level control valves. .The'2 inch bypass
LCV provide better throttling capability at high dP'across the LCV as a
result of ; low SGs pressure and low flow conditions. The upper
.
.
process / safety limit and the lower limit established in this calculation
wereistated to be:
upper process / safety. limit - 485 psi
minimum process / safety limit - 253.4 psi
The inspectors agreed with the licensee's conclusion that no specific -
timing accuracy was required from a safety perspective for switching-
control from the 4 inch LCV to the 2 inch bypass. The switching was
intended to reduce valve maintenance problems.
The licensee's conclusion, as stated on sheet 8. of the calculation was
that the safety limit (s) would not be exceeded due to instrument loop
inaccuracies during normal operation following a seismic event. The
inspectors agreed with the licensee's conclusions on the adequacy of
instrument accuracy determination. The 1-PS-3-138A pressure switch will
perform its safety function. The licensee has agreed to revise the
conclusion statement to reflect that the switch perform its safety
function in the event of an accident or SBO.
Demonstrated Accuracy Calculation (I&C) (1. 2-PS-3-138A)
This calculation was performed to demonstrate that the TDAFW pressure
switch used to ensure that the turbine driven AFW pump would be aligned
> with an intact steam generator had the required accuracy for the -
-function. The subject- pressure switch installed in the MDAFW pump
- discharge line and is used to determine if the pump is delivering _'
- feedwater'(pressure) to the steam generators. If the feed water header
. pressure:does not. increase as required within _a specified time delay,
the control. circuit wil.l cause a transfer of the turbine steam supply to
-
-an intact steam generator. The safety limits as stated in the
calculation Tare maximum _ safety' limit 140 psig and a minimum safety
ilimit of 30 psig; for the switch The pressure switch is located in an
-
.
.
area'(TDAFWR) defined 'as a mild environment for its safety function.
>
<- y
s
I
-
1 f
. .
,
.
37
c. Conclusion
The inspectors agreed with the results of the licensee's' presentation of
AFW instrument accuracy calculations and verified that the instruments
were capable ~of performing their safety function.
E3 Documentation of Desian Bases
E 3.1 Auxiliary Feedwater Desian Criteria SON-DC-13 9 8 Rev.10
a. Insoection Scooe
The inspectors reviewed the licensee's AFW. ERCW. and CST design
criteria. This review was for establishing design-basis parameters
associated with operation and shutdown of the AFW system,
b, Observations and Findinas
The inspectors' review concluded that the AFW design criteria was
comprehensive and of a high quality. However, the inspectors discovered
that the design criteria was revised twice within the inspection period.
Revision 9 was due to self assessment corrective actions and editorial
and typographical changes. Revision 10 was due to the inspectors'
finding on the inconsistency between the design basis calculation
pressure drop values across the MD AFW venturis and the value documented
in Section 3.7.2.1 of the design criteria, in addition to other
typographical errors.
Another inconsistency identified by the inspectors was related to
Section 3.2.3. " Loss of All Alternating Current Power (Station Blackout
SBO)." As stated in this scction ~ .and which are capable of
maintaining the plant at hot shutdown until alternating current power is
restored. The TDAFWP shall satisfy these requirements." This statement
was inconsistent with UFSAR Section 3. which stated that SON is a hot
standby plant. The licensing basis for Sequoyah hot standby and this
statement in 50N-DC-13.9.8. Rev. 10 was therefore incorrect.
Another inconsistency identified by the inspectors was related to the
use of process limits in lieu of safety limits. Calculation 1-PS-3-139A
and SON-CA-D053-0-HCG-LCS-110882 identified pressure switch PS3-139A.B.D
as having a safety limits of 2.4 psig. However. Table 1 of the design
criteria identified this limit as a process limit.
,
b
. .
,
.
38
c. Conclusion
The inspectors' review concluded that these inconsistencies were minor
and did not affect the system's operability. This has been categorized
as the licensee's lack of attention to details and weakness in
implementation of the design control program.
E7 Ouality Assurance in Enaineerina Activities
a. Scope
The inspectors assessed the quality of licensee design documentation as
demonstrated by on-site review of calculations and technical evaluations
and licensee findings from their AFW design audit performed prior to
this inspection.
.
b. Observations and Findinas
The inspectors noted several examples of errors in calculations and
technical evaluations. These included a technical evaluation to
determine shaft torque due to an increase in operating speed
accomplished by DCN M-11853A. A design input in this evaluation listed
a horsepower value corresponding to a specific speed and referenced a
vendor technical performance data sheet as the source. This input was
not consistent with the technical data sheet and had not been verified.
A technical evaluation in PER S0962788 incorrectly calculated the new
2A-A MDAFWP pump power requirement due to a change in the impeller
clearance. The licensee's Sequoyah AFW System Self-Assessment. SA-E&M-
98-001, dated December 4,1997, identified examples in which incorrect
methodologies were used to develop drift, temperature, radiation and
seismic uncertainty values for instrumentation loops and to develop
cable lengths. Additionally, many of the AFW design calculations
reviewed by the inspectors had been recently revised to correct errors
identified by the licensee's audit. The inspectors identified no
examples in which design document errors resulted in a safety concern.
However, the errors do indicate a deficiency in the quality of
calculations and design documentation. The examples above demonstrated
a weakness in engineering performance related to the quality of the
independent review function for design documentation and technical
evaluations,
c. Conclusion
Calculation and technical evaluation document errors identified by the
inspectors and the licensee's pre-inspection demonstrated an engineering
performance weakness related to the quality of the independent review
function.
o )
. . .
,
.
39-
V. MANAr# MENT MEETINGS
X1 Exit Meeting Summary
The Team Leader discussed the progress of the inspection with. licensee
-
representatives on a daily basis and presented the results to members of
licensee management and staff at the conclusion ~of the inspection on
February 13. 1998. The licensee dissented with an inspection finding
involving a potential enforcement item concerning failure to perform a
10 CFR 50.59 Safety Evaluation-for changes made to motor driven AFW
pumps during maintenance.
PARTIAL LIST OF PERSONS CONTACTED
Licensee
J. Bailey, Vice President, Engineering and Technical Services
M. Bajestani. Site Vice President
R. Baron. General Manager North Anna
C. Burton, Engineering and Supervisor Manager
H. Buttenvorth. OPS Manager -
E. Freeman. Maintenance and Moderation Manager
J. Gudel. General Manager
J. Herron. Plant Manager
D. Koehl. Assistant Plant Manager
R. Norton Site Quality Manager
H. Rogers. NSSS System Engineering Manager
P. Salus. Licensing and Industry Manager
J. Smith. Site Licensing Supervisor
J. Summy. Assistance PH Manager
EC
C. Casto. Deputy Director. Division of Reactor Safety
S Khablir. Consultant
.
R. Moore. Reactor Inspector
.S. Rohrer. NRC Graduate Fellow
C. Smith. Senior Reactor Inspector
D. Tondi. Consultant
LIST OF INSPECTION PROCEDURES USED
IP 37550- Engineering
IP 93809 . Safety System Engineering Inspection (SSEI)
o
. .
4
40
LIST OF ITEMS OPFE Q
Ooened-
, Iypa Item No. Descriotional Reference
.
VIO 50-328/98-01-01 Failure to perform 10 CFR 50.59
Safety Evaluation (Section M2.3)
URI 50-327.328/98-01-02 Accident analysis assumption for 10
minutes operation action not-
verified or validated (Section 03)
IFI 50-327.328/98-01-03 Formation of vortices in AFW pumps
suction piping (Section E2.1.1)
IFI 50-327.328/98-01-04 Nonconservative Froude number used
in vortex analysis (Section E2.1.2)
IFI 50-327.328/98-01-05 TDAFW Pump Room DC Exhaust Fan E0
(Section E2.1.3)
IFI 50-327.328/98-01-06 Terry Turbine Governor Minimum i
Voltage Requirements. (Section
E2.2.6)
IFI 50-327.328/98-01-07 Review Wylie Laboratory Battery
Seismic Qualification Test Report
(Section El.1)
Acronym List
CST Condensate Storage Tank
ECCS Emergency Core Cooling System
ERCW Essential Raw Cooling Water
FSAR Final Safety Analysis Report
LCV Level Control Valve
MOV Motor Operated Valve
-MRC Management Review Committee
PER Problem Evaluation Report
SB0 Station Blackout
TDAFWP. Turbine Driven AFW Pump
TDH Total Developed Head
TS. Technical Specification
, !
. .
,
. .
i
-41
l
APPENDIX
L LIST OF DOCUMENTS REVIEWED {
OPERATIONS / MAINTENANCE ENGINEERING INTERFACE REFERENCES
PROCEDURES. DRAWINGS. AND DESIGN DOCUMENTS REVIEWED
DRAWINGS
CCD 1. 2-47W803-3 REV 13. Flow Diagram Auxiliary Feedwater
VENDOR MANUAL-
l
SON-VTM-1075-0250. Vendor Tech'nical Manual-for Ingersoll - Rand Company
Auxiliary Feedwater pumps and Controls. Rev. 13. dated 12/19/97
'
PROCEDURES
'
'
. SSP-6.7. . Control of' Measuring and Test Equipment. Rev. 6 l
l
1-SI-SXP-003-201. A. Motor Driven Auxiliary feedwater pump 1A-A Performance
Test. dated October 20. 1997
SSP-9.3 Plant Modifications and Design Change Control. Rev.18. dated 10/3/97
l
10'CFR 50.59 Evaluations of Changes. Tests and Experim nts. Rev. O. dated
-3/31/97~
<
I
<1-SI-SXP-003-201-B. Motor Driven Auxiliary Feedwater Pump 1 B-B Pump
Performance Test. Rev. 2. dated 6/17/97
l 1-SI-SXP-003-201.S. Turbine Driven Auxiliary Feed Water Pump 1A-S Performance
l . Test, dated November 10. 1997
0-MI-HMV-317-144.'0.. Procedure for. Testing Motor Operated Valves Using MOVATS
Signature Analysis System..Rev.16. dated 9/15/95
- 1-SI-ICC-003-121.0.. Calibration and Functional Test of Condensate Storage Tank
-- Suction Header Pressure Switches to AFW System (PS-3-121A. PS-3-121B. and PS-
.
3-121D). dated December' 30..1997.
p 1-SI EDC-003-180.0? Set point- Verification and-Calibration of AFW Suction ,
1. Transfer System 3 Time Delay Relays, dated September 15, 1997 )
,
)
( '
. .
,
.
42'
'l-PI-SFT-003-001.A. ' Motor Driven Auxiliary Feedwater Pump 1A-A Full Flow Test,
Rev.'3, dated 3/12/97
~
1-PI-SFT-003-001.C. TDAFW Pump Full. Flow Test. Rev. 1, dated 3/21/97
~
1-SI-SXV-003-232.0, MDAFW Pump Check Valve Test During Hot Standby and Hot-
Shutdown. Rev. O. dated 12/13/95
0-SI-SXI-000-200.0- ASME Section XI In service Pressure Test Scheduling and
,
Tracking, Rev. 1, dated 8/26/97.
1-SI-SXI-003-005.0, In service Test of the AFW Pump 1A-S Steam Supply Piping.
Rev. 0,. dated 8/5/95'
-1-SI-SXI-003-004.0..In service Pressure Test of AFW System. Rev. 1. 7/25/95
1-SI-SXI-003-003.b.-In service Pressure Test of MDAFW 1B-B.:Rev. O. dated
8/2/90
1-SI-0PS 003-005.M. ' AFW Valve Position Verification. Rev.1. dated 8/28/97
1-SI-SXI-003-002, Functional Pressure, Test of ERCW. Supply to AFW, Rev. 0,
dated 9/28/90
1 OPOS-003-118.0, AFW Pump and Valve Automatic Actuation, Rev. 4. dated
EA-3-1, Main Control Room Operation of TDAFW Pump. Rev. 4
>
<
EA-3-2, Local-Control of TDAFW Pumps. Rev. 3
EA-3-7, Local Operation of TDAFW Pump After Loss of DC Control Power, Rev. 2
MECHANICAL DESIGN REVIEW REFERENCES
SON-CA'-053-0-HCG-LCS-113082 Rev. 3 SON AFW System Motor Driven and Turbine
Driven ~ Pump NPSH Analysis
SON-31C-D053-EPM RG-060987. Rev. 1. HVAC Equipment Requirements Evaluation:
TDAFW Pump Rom'
SON-CA-0053-EPM-JVM-050289_ Rev. 6. Required Stroke for Auxiliary Feedwater !
'
' Motor Driven Pump LCV's
LCalculation 2219280000. Minimum Head required for the TD and MD AFW pumps
- Rev.:11
~
b
, j
. .
,
.
43
Calculation Auxiliary Feedwater System instrument Process / Safety Limits. 50N-
CA-0053-0-HCG-LCS-032384 Rev. 17
Calculation Analysis to support changing TDAFW LCV's actuator and sizing
criteria of the air cylinder. SON-03-0053-EPM-NOL-021993 Rev. 2
Calculation AFW system recirc. Line final orifice. SON-03-D053-EPM-VIK-040391
Rev. 6
Design Change Notice M10298A
Calculation Auxiliary Feedwater System Pressure Switch Analytical Limits SON-
CA-D053-0-HCG-LCS-110882 Rev. 9
Calculation Demonstrated Accuracy Calculation 1-PS-3-139A Rev. 4
Calculation Condensate Storage Tank (CST) Usable Volume for AFW Use. SON-03-
D053-EPM-GLC-031193 Rev. 2
1-SI-SXP-003-201.S. TDAFW pump 1A-s Performance Test Rev. 1
1-PI-SFT-003-001.C. TDAFW pump Full Flow Test Rev. 1
EA-3-8. Emergency Abnormal Procedure. Manual Control of AFW Flow Rev. 3
1-PI-SFT-003-001.B. MDAFW Pump 1B-B Full Flow Test Rev. 4
1-PI-SFT-003-001.A. MDAFW Pump 1A-A Full Flow Test Rev. 3
ECA-0.0. Emergency Contingency Action Procedure. Loss of All AC Power Rev. 13
Design Change Notice M06185B
Postulated Pipe Break Location Summary AFW System. MCL B05 CEB-PR/N2-096
Rev., 12
Documentation of Design Basis review, required thrust calculation and valve
and actuator. capability assessment for 1-FCV-03-116A. Rev. 2
Flow Diagram Heating & Ventilation Air Flow 1, 2-47W866-2 Rev.10
.
Flow Diagram Auxiliary.Feedwater 1, 2-47W803-2 Rev 51
_
Mechanical Control Diagram Auxiliary Feedwater System 1-47W610-3-3 Rev. 16
-Mechanical Control Diagram Auxiliary Feedwater System 2-47W610-3-3 Rev.18
1
' -
.
.
44
Flow Diagram Feedwater System 1. 2-47W803-1 Rev. 70
Mechanical Control Diagram Main & Aux Feedwater System 1-47W610-3-1 Rev. 8
Mechanical Control Diagram Main &_ Aux Feedwater System 2-47W610-3-1 Rev. 11
Mechanical Control Diagram Main & Aux Feedwater System 1-47W610-3-2 Rev. 13
Mechanical Control Diagram Main & Aux Feedwater System 2-47W610-3-2 Rev. 14
Mechanical Logic Diagram Auxiliary Feedwater System 1. 2-47W611-3-3 Rev. 22
Mechanical Control Diagram Feedwater ',ontrol System 1, 2-47W610-46-1 Rev. 7
Mechanical Logic Diagram Auxiliary Feedwater System 1. 2-47W611-3-4 Rev. 13
Mechanical Logic diagram ESSN Raw Cooling Water 1. 2-47W611-67-3 Rev. 22
Mechanical Logic diagram Essential Raw Cooling Water 1. 2-47W611-67-4 Rev. 15
ELECTRICAL I&C DESIGN REVIEW REFERENCES
FSAR (Section from Chapters 8.3 and 10.4)
Technical Specification
.NUREG 1232. Vol. 2
NRC'SSER - SB0 Analysis
SA-EEM-98-001-AFW System Engineer Assessment
SON-CA-0053-0-HCG-LCS-032384. Rev. 17
SON-EEB-MS-TIO6-0002 (1-8-98) (AFW Motor Evaluation)
SON-SOS 2-007. Rev. 2
SON-VD-VDC-1 Vital Instrument Power System Design Verification
SCG-4M-00894 (attached QA Record Battery Seismic Qualification)
SQN-31C-0053. Rev. 1
. SON-DC-V21.0 (excerpts and tables) Environmental Design
SON-CPS-057 (Battery 1 Load. Inverter Load Table A.6 Loading Summary
<
.-
- . _- -
. .
,
.,
45
SON-VD-VCC1. Appendix 11
CCD No: 1, 2-47W920-9 (DWG Battery Room H&V)
DCN (MO-9007A) PCN 798/ Issue No. 91517 OA Record Replaced 125 Volt Battery
SON-DBD-DC Design Basis Document (Design Criteria)
SON-CA-0053-0-HCG-LCS-110884 Rev 17 AFW System Inst Process / Safety Limits
SON-APS-018. Rev. 12 excerpts (D.C.MOV 1-FCV-1-51)
SON-APS-025 for 2-FCV-1-51)
SON-VP-Volts DC-001. Rev. 25. Appendix 11. TDAFWP Circuit Analysis
Inspection Report 50-327/97-9 H. F. Issues
SON-EPS-006. Cable Ampacity Study Voltage 120 Volts AC.125
SON-EPS-007. Ampacity Study -480 Volts AC Level Cables Route in T rays
SON-EPS-008. Cable Ampacity Study -480 Volts AC and 6900 Volts AC in conduit
.
SON-CSS-002, Cable Ampacity Sampling Program
SON-CPS-051
SON-CPS-057
1-TS-17A Demonstrated Accuracy Calculation. R7
1-PS-3-138A Demonstrated Accuracy Calculation. R4
'
SON-CPS-060
SON-CPS-013
SON-CPS-003
SON-DC-V-13,9.8. Rev. 8
. SON-EEB-MS-T-128- 006 Rev. 6- 005 Rev. 4
Ingersoll-Rand Curve No. C0874140B dated July. 15. 1997
v-
-
N
- _. t
. .
,
.
46
-Ingersoll-Dresser Pump Company Order 073-62227 Speed-Torque Curve, dated
February 9, 1998
Allis Chalmers Manufacturing Co Order No. 8-5112-90194-1. Report of Test
Induction Motor
Allis Chalmers 500 HP. 6600V.3 Phase. 60 Cycle 3600 RPM Motor Speed-Torque
Curve
Calculation No. SON-EEB-MS-T106-0002 Auxiliary Power System
Analysis. Revision 37
Design Guide DG-EZ-4-6 Table 1-3. Typical Impedance of 8000 V Cooper Conductor
Cable in OHM Per 1000 Feet-Phase. Revision 2
i