ML20195F780
| ML20195F780 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 06/10/1999 |
| From: | Muench R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20195F787 | List: |
| References | |
| ET-99-0018, ET-99-18, NUDOCS 9906150094 | |
| Download: ML20195F780 (13) | |
Text
E x:
P LFCREEK W8) NUCLEAR OPERATING Richard A. Manch Vice President Engineering JUN 101999 ET 99-0018 U.
S.~ Nuclear Regulatory Commirrion ATTN:
Document _ Control Desk Mail Station Pl-137 Washington, D. C. 20555
Subject:
Docket No.
50-482:
Proposed Revision to Technical Specification Table 3.3-4, Functional Unit 7.b.,
Automatic Switchover to Containment Sump (RWST Level - Low-Low)
Gentlemen This letter transmits an. application for amendment to Facility Operating License No. NPF-42 for the Wolf. Creek Generating Station (WCGS). This request proposes to revise the Z,
S and Allowable Value terms for current Technical Specification Table 3.3-4, Functional' Unit 7.b.,'
Automatic Switchover to Containment Sump (RWST Level - Low-Low).
A safety evaluation is provided in Attachment I.
A No Significant Hazards Consideration Determination is provided in Attachment' II.
Attachment III is the related Environmental Impact Determination.
Marked up pages are provided in Attachment IV (for current Technical Specifications and Bases) and in Attachment V (for improved Technical Specifications and Bases as approved by Amendment No. 123).
Attachment VI provides'a listing of commitments made in l
this submittal.
I In accordance with 10 CFR 50.91, a copy of this application, with attachments, is being provided to the designated Kansas State Official.
This proposed
/j revision to the WCGS current Technical Specifications will be fully
//
bplemented within 60 days of formal NRC approval.
b If you have any questions concerning this matter, please contact me at (316) j/
364-4034, or Mr. Michael J. Angus, at (316) 364-4077.
i Ve tru
- yours,
/d/4 Richar A. Muench l
l RAM /rir i
i Attachments:
I
- Safety Evaluation II
-- No Significant Hazards Consideration Determination III - Environmental Impact Determination IV
- Proposed Current Technical Specification Change V
- Proposed Improved Technical Specification Change VI
- List of Commitments cc:
V. L. Cooper (KDHE), w/a
}[
W. D. Johnson (NRC). w/a
- 1; ',.
E. W. Merschoff (NRC), w/a K. M.
Thomas (NRC), w/a f
Senior Resident Inspector (NRC), w/a 9906150094 990610 PDR ADOCF ~5000482 [
P PDR
]
, KS 66839 i Phone: (316) 36L8831 An Equal Opgxxturwty Em(doyer Mf HCNET
fg I
t.
I j
i I
STATE.OF KANSAS
)
L
)
ss l
COUNTY OF COFFEY. '):
1 Richard A. Muench, of lawful age, being~first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the. foregoing document and - knows the content thereof; that he has executed that same for and on behalf-of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.
By
/
Richard A Muench Vice Pre ident Engineering u
SUBSCRIDED'and sworn to before me this
/O day o'f T uwe 1999.
m Notary Pubjic U
uy Appt es,7/8/onnu Expiration Date 7/I/AOoA
/ (
i i
i
Xttachm:nt I to ET 99-0018 Pags 1 of.5 1
0 0
l i
1 ATTACHMENT I SAFETY EVALUATION l
i 4
i l
1 1
]
{
99-0018 i
l Attachment I to ET
)
i Page 2 of 5
(
Safety Evaluation Proposed Changes This license amendment request proposes to revise the Z, S and Allo able Value I
terms for the Wolf Creek Generating Station (WCGS) current Technical Specifications Table 3.3-4, Functional Unit 7.b.,
Automatic Swituover to Containment Sump (RWST Level - Low-Low).
The associated changes to the improved Technical Specifications, as approved by Amendment No.
123, are j
provided in Attachment V.
The proposed revision incorporates new values based on calculations that consider the density variations due to temperature and a
boric acid concentrations.
Specifically, the amendment request proposes the following changes to Technical Specification Table 3.3-4, Functional Unit 7.b.:
RWST Level - Low-law SENSOR ALLOWABLE Z
ERROR (S)
VALUE 1.65 1.82 35.5%
3ackground I
The Refueling Water Storage Tank (RWST) supplies both trains of the Emergency Core Cooling System (ECCS) and the Containment Spray System through a common suction line to each system's supply header during the injection phase of a loss of coolant accident (LOCA) recovery.
At the end of the injection phase of a LOCA, the source of water for the low pressure ECCS pumps or residual heat removal (RHR) pumps is automatically switched to the containment recirculation sumps.
A motor operated isolation valve is provided in each l
header to isolate the RWST from the ECCS once the system has been transferred to the recirculation mode.
The recirculation mode is entered when pump suction is transferred to the containment sump following receipt of the RWST Level Low-Low 1 Automatic Transfer Signal coincident with a Safety Injection (SI) signal.
Following switchover to the recirculation mode, the low head RHR pumps and containment spray pumps draw the water from the containment recirculation sumps, the RHR pumps pump the water through the RHR heat exchanger, inject the water back into the Reactor Coolant System (RCS), and supply the cooled water to the high pressure ECCS pumps.
Switchover from the RWST to the containment l
sumps must occur before the RWST empties to prevent damage to the RHR pumps and a loss of core cooling capability.
For similar reasons, switchover must not occur before there is sufficient water in the containment numps to support ECCS pump suction.
During the injection phase of a LOCA, the RWST is the source of w ter for all j
ECCS pumps.
A Lcu Low-l level in the RWST coincident with an SI signal i
provides protectior, ar,ainst a loss of water for the ECCS pumps and indicates
)
the end of the injection paase of the LOCA.
The RWST is equipped with four safety related level transmitters (LT-930, LT-931, LT-932 and LT-933).
These transmitters indicate 0-100% on the main control board.
Each transmitter j
feeds five separate bistables.
The alarm setpoints associated with the five j
bistables are: HA (99.8%), Low (96.8%), Low Low-1 (36%), Low Low-2 (11.1%),
and Empty (5.6%).
These transmitters provide no control functions.
Therefore, a two-out-of-four logic is adequate to initiate the protection function actuation.
Although only three channels would be sufficient, a fourth channel has been added for increased reliability.
The RWST Low Low-l Allowable Value/ Trip Setpoint is selected to ensure adequate water remains in the RWST to complete the switchover to the i
l II L
I
r
$ttachment I to ET 99-0010
/:
Page'3 of 5 containment sumps.
The current Technical Specification Trip Setpoint of 2 36%
o,f inst,rument span and a Allowable Value of 2 35.1% of instrument span include consideration of instrument uncertainty.
The Trip Setpoints are the nominal values at which the bistables are set.
Any bistable is considered. to be proparly adjusted when the as-left value is within the two-sided calibration tolerance band for the bistable.
The actual nominal Trip Setpoint entered into the bistable is typically more conservative than that specified by the Allowable Value to account for changes in random measurement errors detectable by an ANALOG CHANNEL OPERATIONAL TEST (ACOT).
One example of such, a change in measurement error is drift during the surreillLnce interval.. If the measured setpoint does not exceed the Allowable Value, the bistable is considered OPERABLE.
Conformance with the Technical Specifications is verified by performance of an ACOT.
For each ACOT, the bistable's Trip Setpoint is determined by injecting i
a known signal at the input to, the process racks.
If the as-found Trip Setpoint is within the calibration tolerance band the channel is considered 1
OPERABLE with no furtbor action required.
If the as-found Trip Setpoint is outside 'the calibration tolerance band but more conservatite than the Allowable.Value,-it is considered OPERABLE, but is recalibrated to within the calibration tolerance.
If the as-found Trip Setpoint is less conservative than the Allowable Value, the OPERABILITY in determined by satisfying the equation: Z + R+S $ TA or declaring the channel inoperable in accordance with current Technical Specification 3.3.2, Action b.
In the improved Technical Specifications, as approved by Amendment No. 123, if the as-found Trip Setpoint is greater than the Allowable Value during the performance of the CHANNEL OPERATION TEST, the channel is declared inoperable.
The relationship between the Z,
R, S and TA terms 3s given in Technical Specification 3.3.2, Equation 2.2-1 as Z + R + S $ TA.
Where:
Z=
The value from Column Z of Table 3.3-4 for the affected channel, j
R=
The "as measured" value (in percent sparu of rack (R) error for j
the affected channel, S=
Either the "as measured" value (in percent span) of the sensor l
error, or the value from Column S (Sensor Error) of Table 3.3-4 l
for the affected channel, and 1
TA = The value from Column TA (Total Allowance) of Table 3.3-4 for the affected channel.
)
Topical Report TR 89-001, "WCNOC Nuclear Safety Analysis Setpoint Methodology for-the Reactor Protection System" provides the detailed description of the methodologies used to calculate the nominal Trip Setpoints and Allowable Values. 'The Z value is further defined as the Square Root of the Sum of the
)
Squares (SRSS) of those terms for which there is no periodic surveillance (e.g.,
process measurement accuracy, primary element accuracy, etc.)
and which is then arithmetically summed with the Environmental Allowance term.
The Total Allowance value is the difference between Safety Analysis Limit and the nominal Trip Setpoint.
The Total Allowance value accounts for channel uncertainty -(Channel Statistical Allowance) and margin.
Margin is the difference between the Total Allowance and Channel Statistical A'.lowance and is used to change tbo Trlp Setpoint, account for any instrumentation hardware changes, or allow for instrumentation errors not presently identified.
The Allowable Value is that value which allows for deviation (rack drif t and/or calibration tolerances) from the nominal Trip Setpoint.
dttachment I to ET 99-0018 1
Page 4 of 5 Evaluation A's disc'ussed above, the current Technical Specification Trip Setpoint is 2 36%
of instrument span with an Allowable Value of 2 35.1% of instrument spin, and includes consideration of instrument uncertainty.
The four RWST level transmitters are calibrated with water at a reference temperature of 68"F.
This introduces two components of error. One is water density due to a change in temperature.
The other is a bias error in the transmitter span for the differences between the dennity of the boric acid concentration in the RWST and the density of the water used for calibration at the same temperature.
The RWST instrument loop uncertainty calculation, associated with the current Technical Specification values, did not consider the density variations due to temperature and boric acid concentration.
A revised calculation of the RWST level instrument uncertainty Lad Technical Specification values was performed in accordance with TR 89-001, "WCNOC Nuclear Safety Analysis Setpoint Methodology for the Reactor Protection l
System."
The Margin on the RWST level instrument loop was small in the original uncertainty calculation.
This revised calculation includes the temperature density correction of 0.088% of instrument span in the SRSS of those terms for which there is no periodic surveillance (e.g.,
process measurement accuracy) and includes the boric acid density correction of 0.437%
of instrument span as a separate bias term.
With the addition of the l
corrections in density for temperature and boric acid, the Z term value increased to 1.65% which resulted in the Margin being eliminated.
This will have the effect of decreasing the amount that the rack (R) and sensor error I
(S) terms can deviate from normal and still meet the requirements of Equation 2.2-1.
Therefore, other components (e.g.,
rack drift and rack and sensor measurement and test equipment) used in determining the Channel Statistical Allowance were reviewed to regain some of the Margin that was eliminated.
(
1 The original uncertainty calculation assumed a value of 1% for rack drift.
Based on previous plant data it was determined that the rack drift for the RWST level instrumentation was minimal.
The ACOT results for this instrument loop for the previous seven years indicate that the measured rack drift values are on the order of 0.25% of instrument span.
Based on this data, a reduced rack drift value of 0.5% of instrument span was assumed in the revised calculation.
Additionally, measurement and test equipment imprevements since initial plant startup have been made that allow for a reduction of the value for rack measurements.
The revised calculation accounts fer a total of 1.40%
of instrument span in rack errors.
The original calculation accounted for 1.95% of instrument span in rack errors.
This results in a decrease in the rack error (R) term values when determining the Channel Statistical Allowance.
The rack error (R) term value is not specified in the Technical Specifications.
l The sensor measurement and test equipment value was reduced to 0.323% from 0.36% of instrument span.
Reducing this value is acceptable based on the use of a precision pressure gauge which has an improved accuracy over the original l
type of equipment assumed in the original methodology.
This results in a small decrease in the sensor error (S) term which further assists in meeting the requirements of Equation 2.2-1.
The other sensor errors remained the same.
Based on the changes to the Channel Statistical Allowance describe above, the RWST level instrumentation Allowable Value was recalculated which resulted in an increase in the Allowable Value.
The Allowable Value increase is more restrictive than the current value which results in the Allowable Value being the same as the calicration tolerance band.
The increased Allowable Value to the calibration tolerance band is acceptable cince the measurement error (e.g.,
instrument drift) has been insignificant during the surveillance
~
p.
.$ttachment I to ET 99-0018 Paga 5 of 5.
interval and the quarterly ACOTs have demonstrated that the instrumentation has. remained well within the calibration tolerance band.
The results. of thic. calculation identified that the current Technical Specification value for.the Z term be revised from 1.21 to 1.65, the sensor error (S term) be revised from.1.86 to'1 82, and the Allowable Value from 2 35.1% of instrument span to 2 35.5% of instrument span.
The nominal Trip Setpoint remains.at 2 36% of instrument spcn.
An' ACOT is. performed quarterly in accordance with. current Technical Specificaticn Table 4.3-2, Functional Unit 7.b.
This quarterly surveillance verifles that the rack drift is maintained within 0.5% of the nominal Trip Setpoint. The ACOT includes adjustments as necessary, of the alarm, interlock and/or Trip Setpoints such that the Setpoints are within the required range and accuracy.
Administrative controls have been established to account for the increase in the Allowable Value as discussed in Administrative Letter 98-10, "Dispositioning of Technical Specifications That are Insufficient to Assure Plant Safety."
The changes to the Z and S terms and the Allowable Value do not impact the
-ECCS injection volume.
The Safety Analysis Limit and nominal Trip Setpoints are not affected when accounting for the density variations due to temperature and boric acid concentrations.
Consequently, adequate water remains in the RWST following receipt of the RWST Level Low-Low 1 signal to complete switchover of the ECCS pumps for recirculation.
Additionally, the changes to the Z and S terms and the Allowable Value have no impact on Containment Spray System operation.
Other RWST level setpoints exist to ensure a timely switchover of the containment spray pumps to the containment sumps as a suction sourco.
Amendment No. 123, dated March 23, 1999, converts the current WCGS Technical Specifications to the improved Technical Specifications.
Attachment V to this letter provides proposed changes to the improved Technical Specifications (which are scheduled to be implemented by December 31, 1999).
Conclusion The proposed changes impose.a more restrictive Allowable Value than currently exists in the WCGS Technical Specifications.
These changes are censistent with the revised uncertainty calculation and irclude corrections for temperature and boric acid density.and ensures OPERABILITY of the instrumentation critical to ECCS switchover from injection to cold leg
. recirculation.
j r
I" ~
j dttachmint II to ET 99-0018 Paga 1 of 3 t
e ATTACHMENT II NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION
'Ettachmsnt-II to ET 99-0018
~
Pags,2 of'3 No Significant Hazards Consideration Determination Propoeed Changes This license amendment request proposes to revise the Z, S and Allowable Value
. terms for the Wolf Creek Generating Station (WCGS) current Technical Specifications Table 3.3-4, Functional Unit 7 b.,
Automatic Switchover to Containment Sump (RWST Level - Low-Low).
The associated changes to the improved Technical Specifications, as approved by ' Amendment No.
123, are provided in Attachment V.
The proposed revision incorporates new values based on calculations that consider the density variations due to temperature and
. boric acid concentrations.
'Specifically, 'the amendment request proposes the following changes to Technical Specification Table 3.3-4, Functional Unit 7.b.:
RWST Level - Low-Low SENSOR ALLOWABLE Z
ERROR (S)
VALUE 1.65 1.82 35.5%
-Application of Standards The following Standards identified in 10 CFR 50.92 have been used to determine whether the proposed changes involve a Significant Hazards Consideration.
Each of the identified proposed changes is evaluated against the three Standards.
Standard I - Involve a Significant Increase in the Probability or Consequences of an Accident Previously Evaluated The protection system performance will remain within the bounds of the previously performed accident analysis.
The protection systems will continue to function in a manner consistent with the plant design basis.
The proposed changes will not affect any of the analysis assumptions for any of the acciden'ts previously evaluated, since the changes are consistent with the setpoint methodology and ensure adequate margin to the Safety Analysis Limit.
The proposed changes will not affect any event initiators nor will the proposed changes affect the ability of any safety related equipment to perform its intended function. There will be no degradation in the performance of nor an increase in the number of challenges imposed on safety related equipment assumed to function during an accident situation.
There will be no change to l -
normal plant operating parameters or accident mitigation capabilities.
Therefore these changes do not involve a significant increase in the l
probability or consequences of an accident previously evaluated.
Standard II - Create the Possibility of a New or Different Kind of Accident from any Previously Evaluated There are no changes in the method by which any safety related plant system performs-its safety function.
The normal manner of plant operation remains j
unchanged, and no new equipment is being introduced.
The increase in the RWST Level Low-Low Al]owable Value still provides acceptable margin between the nominal Trip Setpoint and Allowable Value while taking into account a i
temperature and boric acid density correction.
The change in '.:!owable Value I
-does not - impact the systems capability to perform an ECCS switchover from l
injection to cold leg recirculation since the nominal Trip Setpoint remains i
the same.
The change in Allowable Value also will not affect injection or recirculation of the Containment Spray System.
p e
dttachmsnt II-to~ET 99-0018
'Pege 3 of 3 s
No' new accident scenarios, transient precursors, failure mechanisms, or limitingLsingle failures are introduced as a result of the proposed changue.
' ' Therefore, - the. proposed ' change-does not create the possibility of a new or different kind of accident-from any previously evaluated.
Standard III -. Involve a Significant Reduction in the Margin of Safety The1 ' proposed 1 changes do not affect the acceptance criteria for any analyzed event nor is'there a change in any Safety Analysis Limit.
There will be no
'effect on the ' manner in - which safety limits or Engineered Safety Features Actuation System settings.are determined nor will there be any affect on-those plant systems necessary to assure the accomplishment.of protection functions.
Therefore,'there will be no impact on any margin of safety.
4
~
Conclusions Based on the 'above ' discussions,. it has been determined that the requested technical specification revisions do not involve a significant increase in the probability of. consequences of an accident or other adverse conditions over
. previous evaluations; or create the possibility of a new or different kind of accident or condition over ' previous evaluations;.or involve 'a significant
]
reduction in a margin of safety.
Therefore, the requested license amendment does not involve a'significant hazards consideration.
1
)
q a
)
i I
4ttachm:nt III to ET 99-0018 Paga 1 of 2
)
9 ATTACHMENT III I
ENVIRONMENTAL IMPACT DETERMINATION l
l I
I l
[
i 1
i
I' dttachmsnt-III to ET 99-0018 Paga 2 of 2 l
l Environmental Impact Determination
.This li' cense amendment request proposes to revise the Z, S and Allowable Value terms for the Wolf Creek Generating Station (WCGS) current Technical Specifications Table 3.3-4, Functional Unit 7.b.,
Automatic Switchover to i
Containment Sump (RWST Level - Low-Low).
The associated changes to the improved Technical Specifications, as approved by Amendment No.
123, are provided in Attachment V.
The proposed revision incorporates new values based on calculations that consider the density variations due to temperature and boric acid concentrations.
Specifically, the amendment request proposes the following changes to Technical Specification Table 3.3-4, Functional Unit 7.b.:
RWST Level - Low-Low SENSOR ALLOWABLE i
Z ERROR (S)
VALUE 1.65 1.82 35.5%
10 CFR 51.22(b) specifies the criteria for categorical exclusions from the 1
requirement for a-specific environmental assessment per 10 CFR 51.21.
This amendment rsquest meets the criteria specified in 10 CFR 51. 22 (c) ( 9) as specified below-(i) the amendment involves no significant hazards consideration As demonstrated in Attachment II, the proposed changes do not involve any significant. hazards consideration.
1 (ii) there is no significant change in the types or significant increase in the amounts of any effluents that may be released offsite None of the proposed changes involves a change to the facility or operating procedures that would cause an increase in the amounts of effluents or create new types of effluents, since accident analysis assumptions remain unchanged and Safety Analysis Limit margins are adequately protected.
(iii) there is no significant increase in individual or cumulative occupational radiation exposure The proposed change is administrative in nature and does require any changes to Trip Setpoints.
These changes have no relation to occupational radiation exposure, either individual or cumulative.
Based on the above, it is concluded that there will be no impact on the environment resulting from this change and the change meets the criteria
~
specified in 10 CFR 51.22 for a categorical exclusion from the requirements of 10 CFR 51.21 relative to requiring a specific environmental assessment by the Commission.
1
3-Ittachmsnt IV to ET 99-0018 Pags 1 of 2 l
ATTACHMENT IV
)
PROPOSED TECHNICAL SPECIriC,' TION CHANGES CURRENT TECHNICAL SPECIFICATIONS I
I l