ML20127B697
| ML20127B697 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/30/1992 |
| From: | DUQUESNE LIGHT CO. |
| To: | |
| Shared Package | |
| ML20127B666 | List: |
| References | |
| NUDOCS 9301130068 | |
| Download: ML20127B697 (21) | |
Text
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ATTACHMENT A Beaver Valley Power Station, Unit No. 2 l --
Proposed Technical-Specification Change No._16, Revision-1 PAGES MARKED TO SHOW CHANGES Revise the Technical Specification as follows:.
o Remove Pace Insert Pace i
3/4 3-74 3/4_ 3-74 l
'I 9301130068 921230
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PDR. ADOCK 05000412-i P
NPF-73 INSTRUMENTATION TURBINE OVERSPEED PROTECTION LIMITING 30NDIT10N FAR_0EERAHON 3.3.4 At least one Turbine Overspeed Protection System shall be OPERABLE.
APPLICABILITY:
MODES 1, 2*, and 3*.
ACTION:
a.
With onelstodvalve or one governor valve per high pressure turbine steam line inoperable and/or with one reheat stop valve or one reheat intercept valve per low pressure turbine steam line inoperable, restore the inoperable valve (s) to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or close at least one valve in the affected steam line(s) or isolate the turbine from the steam suppiy within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
b.
With the above required Turbine Overspeed Protection System otherwise inoperable, within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> isolate the turbine from the steam supply.
c.
The provisions of Specification 3.0.4 are not applicable.
EURYELLLAEE_ REQUIREMENTS 4.3.4.1 The provisions of Specification 4.0.4 are not applicable.
4.3.4.2 The above required Turbine Overspeed Protection System shall ha demonstrated OPERABLE:
Y lAt least once per 31 daysi,9y cycling each of the following valves a.
through at least one complete cycle from-the running position:
U 1)
Four h h pressure turbin sto v lve j
s/
af leQSY olice 2)
Four' tippressure turbine governor v u
3)
Four
- 6) pressure turbine reheat stop valve, anciz fer 18 rnonks (M
4)
Four ow pressure turbine reheat intercept va b.
Etleastonceper31daysQy direct observation of the movement of each of thelabovelvalves tarough one complete cycle from the running position, 9' Followincj c.
At least once per 18 months by performing a CHANNEL CALIBRATION on the Turbine Overspeed Protection Systems, and d.
At least once per 40 months by disassembling at least one of each of the above valves and performing a visual and surface inspection of valve seats, disks, and stems and verifying no unacceptable flaws or excessive corrosion.
If unacceptable flaws or excessive corrosion are found, all other valves of that type shall be inspected /unless fhe nahrc the rob m can be chrectl att rksked to a service concllkn
- Speci ficationYo$.la'pplica y
ewithaWm#k$teamNsNationNafvefa"nNasso-a ciated bypass valves in the c_losed position and all other steam flow paths to the turbine isolated.
(,ns >echan cycle mayled here is no kMc k be ir.crecisecl fo a madmum i
of bO months, frovic n of a
Proposecl oferaHonal distress, BEAVER VALLEY - UNIT 2 3/4 3-74
ATTACHMENT B Beaver Valley Power Station, Unit No. 2 Proposed Technical Specification Change No. 16, Revision 1 REVISION OF TURBINE REHEAT STOP AND INTERCEPT VALVE TEST INTERVAL A.
DESCRIPTION OF AMENDMENT REQUEST The proposed amendment replaces our previous submittal dated October 1,
1990, and would make the following changes:
Revise the frequency of reheat stop and intercept valve testing required by Specifications 4.3.4.2.a and 4.3.4.2.b from "at least once per 31 days" to "at least once per 18 months."
Change the words "stop valve," in Action statement "a" and Surveillance 4.3.4.2.a.1.,
to read " throttle valve."
Change the words "high pressure turbine reheat stop valves" in Surveillance Requirement 4.3.4.2.a.3 to read
" low pressure turbine reheat stop valves."
Change the last sentence of Surveillance Requirement 4.3.4.2.d to read as follows (words to be added are shown in brackets):
If unacceptable flaws or excessive corrosion are
- found, all other valves of that type shall be inspected
[unless the nature of the problem can be attributed to a
service condition specific to that-valve).
Add the-following sentence to the end of Surveillance
~
Requirement 4.3.4.2.d.
For reheat stop and intercept valves the inspection cycle may be increased to a
maximum of 60 months, provided there is no indication of operational distress.
B.
BACKGROUND A
calculation was performed to-determine the probability of turbine missile ejection resulting from an extension of the test interval for reheat stop and intercept valves.
It. was determined, based on the calculation, that the turbine missile-generation probability meets the appropriate turbine system reliability criteria (also see Reference 1).
Changing "stop valve" to read
" throttle valve" would.make the wording consistent with the terminology used in the manufacturer's literature and plant documents.
I i
_______________________________________________a
- - ~
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- AThACHMBNTB,' continued
, Proposed Technical Specification Change No. 16, Revision-1 Page 2 Changing the' words "high pressure turbine reheat stop valves" to read
" low pressure turbine reheat stop valves" is an editiorial correction.
The-change -makes the wording reflect the-plant-configuration and is consistent with the wording in Action a, and standard technical specifications.
The words added to the end of Surveillance Requirement 4.3.4.2.d-are intended to eliminate clearly unnecessary inspections, and are not intended to climinate inspections _necessary to achieve the objective of this surveillance requirement. 'The sentence to be added to. Surveillance Requirement
~4.3.~4.2.d-is based on a notification from Westinghouse Electric Corporation that the inspection interval may be increased to a maximum of 60 months
-provided there is_ no indication of operational distress.
A160 month inspection-interval was also assumed in the calculation'of turbine missile ejection probability mentioned above.
C.
JUSTIFICATION Based on the Westinghouse calculation of turbine missile ejection probability, submitted in our letter of May 2;, 1992 (Reference 8
1),
it has-been determined that with an eighteen (18). month-reheat stop-and= intercept valve test interval, the total turbine-m.4ssile generation probability for Beaver Valley Power Station-Unit 2 meets applicable acceptance criteria.
Operating experience and testing at Unit 1
and Unit 2 have disclosed no-significant problems relating to the-proper operation of the. overspeed protection system.
No_ incidents of.
valve stem. sticking have occurred while the' units were carrying-load.
Testing over a
period of time has been found to cause turbine component damage.
In particular, erosion of piping and damage to moisture separator reheater internals.at_ Unit'1.
D.
SAFETY ANALYSIS The_following. paragraphs discuss:
1.
the. Updated Final Safety Analysis _ Report evaluation -of postulated turbine missiles, 2.
evaluation acceptance criteria, 3.
the most recent ~ calculation of turbine missile ejection L
probability (previously submitted by Reference 1),
i
-4.
evaluation results and-conclusions, and S.
other changes.
~_
=
l ATTACHMENT B, continued Proposed Technical Specification Change No. 16, Revision 1 Page 3 Evaluation of Postulated Turbine Missiles The turbine overspeed protection specification is provided to ensure that the turbine is protected from destructive overspeed.
Protection from excessive overspeed is required since excessive overspeed of the turbine could generate potentially damaging missiles that could impact and damage safety related components, equipment, or structures.
Updated Final Safety Analysis Report (UFSAR) Sections 3.5.1.3 and 3.5.1.4 describe the evaluation of postulated turbine missiles <
Both the probability of missile generation and of impact to safety-related items were considered in the UFSAR as described below.
The probability (P4) of damage to plant structures, systems, and components important to safety is:
P4 = P1 x P2 x P3 where:
P1 = the probability of generation and ejection of a high energy
- missile, P2 = the probability that a
missile strikes a critical plant region, given its generation and ejection, and the probability that the missile strike damages its target P3
=
in a
manner leading to unacceptable consequences.
Unacceptable consequences are defined here as the loss of the capacity to maintain the integrity of the reactor coolant pressure boundary, to shut down the plant, maintain
~
it in a
safe shutdown condition, and/or limit offsite radiation exposures.
Evaluation Acceptance Criteria The NRC staff considers 1
x 10-7 per year an acceptable risk rate for the loss of an essential system from a single event (Reference Regulatory Guide 1.115).
Thus, the probability (P4) of damage to plant structures, systems, and components important saf9ty is an acceptable risk for values less than or equal to to per year.
' x 10 (P
is considered The combined probability of strike damage10~gxP3) per year.
This to be less than or equal to 1
x conservatively considers the unfavorable orientation of the turbine generator.
It follows that the probability of turbine missile generatiog (P1) is acceptable for values less than or equal to 1 x 10-per year.
m.s.
s
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t
~ATTACHMINT B, continued Proposed Technical Specification Change No..16, Revision 1 Page 4~
Descrintion of Most Recent Evaluation Three
_overspeed events were-considered in evaluating. the probability for missile ejection: design overspeed (120 percent of rated speed),
intermediate overspeed- (132' percent of rated speed),
and destructive overspeed (speeds greater than' 170 percent of rated speed).
The evaluation of. turbine missile ejection probability focuseo en the design and intermediate 1 overspeed events since. they would be affected by the test intervals of the reheat stop valves and intercept valves.
The destructive overspeed event does not' result from failuresJof reheat stop and intercept valves and therefore was-excluded from further consideration.
The evaluation presents the total probability of turbine missile ejection for the design and intermediate overspeed events given that system separation occurs.
The total probability is based on-conditional probabilities of missile ejection for Unit 1 given-that design or. intermediate overspeed occurs. : Unit 1 conditional probabilities were used since theyfare more conservative than the.
values calculated for Unit 2.
The total probabilities for a missile ejection must be-multiplied by the average annual frequency of system separati~on for the unit so that they can be measured against acceptance criteria.
Based.
on a
review of Unit 2 plant trips,.the average annual frequency.
of system separation was calculated to be.0.22-(one occurrence in four and one-half-years).
To provide additional' conservatism,.
the average annual frequency of system separation was assumed to-be one-half.(0,5).
This value is also conservative for Unit 1.
The evaluation did not
' consider destructive overspeed probability Therefore, the " general" acceptance. criteria of
~g 1
x 10 per -year for turbine ' missile-ejection from an unfavorably oriented-turbine. was-reduced.
. A ten '(10) percent ~
fraction of the " general" acceptance criteria was assumed as the acceptance-criteria for the design and intermediate,overspeed missile probabilities evaluated.
This leaves'an adequate reserve:
margin of 90 percent-of' the acceptance criteria-for'other significant overspeed. events such'as' destructive overspeed.
Evaluation Results and Conclusion The product of the average annual frequency 1of turbine separation-for Unit 2-(conservatively-assumed to be (6.79 x 10~7)he total 0.5) and t
-is less probability of turbine missile ejec thantheacceptancecriteria.of-1'X'10~gion-As stated in the BACKGROUND discussion.above, plant-operating experience-and-testing have disclosed no significant problems-relating to the proper-operation.of the turbine-overspeed protection system.
This taken together with the favorable turbine missile evaluation discussed above indicates-that the
AT'fACHMENT B, continued Proposed Technical Specification Change No. 16, Revision 1 Page 5 turbine system reliability is acceptable with an eighteen (18) month test interval for reheat stop and intercept valves.
Therefore, the test interval extension is considered to be safe and will not reduce the safety of the plant.
Other Changes Changing "stop valve" to read " throttle valve" and "high pressure turbine reheat stop valves" to read " low pressure turbine reheat stop valves" is editorial in
- nature, and does not change or otherwise reduce current requirements.
Therefore, the changes are considered to be safe and will not reduce the safety of the plant.
The words added to the end of Surveillance Requirement 4.3.4.2.d are intended to eliminate clearly unnecessary inspections, and are not intended to eliminate inspections necessary to achieve the objective of the surveillance requirement.
Therefore, the change is considered to be safe and will not reduce the safety of the plant.
The sentence to be added to Surveillance Requirement 4.3.4.2.d permitting a
reheat stop and intercept valve inspection interval extension is based on a notification from Westinghouse Electric Corporation that this inspection interval extension is acceptable.
A sixty month inspection interval was assumed in the calculation of turbine missile ejection probability mentioned above.
Based on this information, the inspection interval extension to 60 months is considered to be safe and will not reduce the safety of the plant.
E.
NO SIGNIFICANT HAZARDS EVALUATION The no significant hazards considerations involved with the proposed amendment have been evaluated, focusing on the three standards set forth in 10 CFR 50.92(c) as quoted below:
The commission may determine, pursuant to the procedures in paragraph 50.91, that a proposed amendment to an operating license for a facility licensed under paragraph 50.21(b) or paragraph 50.22 or for a
testing facility involves no significant hazards consideration, if operation of the facility according to the proposed amendment would not:
(1)
Involve a
significant increase in the probability or consequences of an accident previously evaluated; or (2)
Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of safety.
ATTACHMENT B, continued
. Proposed TechnicalfSpecification Change'No. 16, Revision 1-I Page 6 The following evaluation is provided for the'Eno significant hazards consideration standards.
1.
Does-the change involve a
significant increase in the probability or consequences of an accident previously_
1 evaluated?
I The previously evaluated accident of. interest-is a
destructive turbine overspeed_ event.
The probability of turbine missile ejection with.an extended-(18 month) test' interval for reheat stop and intercept valves-has been determined to be within applicable acceptance criteria.
Therefore, the proposed change does not involve-a significant increase in the-probability or consequences of an accident previously evaluated.
Changing "stop valve" to read
" throttle valve" and "high.
j pressure-turbine reheat stop valves" to read " low pressure i
turbine reheat stop valves" is editorial in nature,fdoes not change or otherwise reduce current requirements and has no-affect on the probability or consequences of an accident previously evaluated.
~
Surveillance Requirement 4.3.4.2.d has been modified' to eliminate clearly unnecessary-inspections, and -is.not intended to eliminate inspections necessary to achieve the-objective of this surveillance requirement.
_-This-clarification does_ not change the
- design, operation,'or failure modes of the valves and other components-in the turbine overspeed protection system. Therefore,_the change does not-involve a significant increase in the prcbability or consequences of_an accident previously evaluated.
q The reheat stop and_. intercept-valve inspection intervalL l
extension does not change the design, operation, or failure-modes of the valves and -other components in the turbine overspeed protection _ _ system.__
- Also, a
sixty _ month inspection interval was assumed in the.previously described calculation of turbine missile ejection-probability.
It was determined that the probability of turbine miasile ejection-is within the applicable acceptance criteria.
Therefore, the _ change' does not involve a significant increase inithe-probability or_
consequences. of; an accident 'previously_
evaluated.
2.
Does the change create the possibility of.a.new or different.
kind of-accident _from any accident previously evaluated?
The change affects the test interval for the reheat stop and l
intercept valves and does not change the design, operation, or failure modes-of'the valves and other components in the turbine overspeed protection system.
Therefore, the proposed change does not create the possibility of-a new or different -kind of accident from any-accident previously evaluated.
l l.
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_ ATh'hCHMENT B, continued Proposed Technical Specification Change No.-16, Revision 1 Page 7 Changing '"stop valvo" to read- - " throttle 1 valve" andx"high.
pressure. turbine reheat.stop valves" to read " low pressure q
turbine reheat stop valves" is editorial in' nature, and does not change the design,- operation, or. failure modes of the valves
.and-other components in_ the turbine overspeed-
-protection system.
-Therefore, the proposed changes-do not create the possibility of a
new or different kind ~ of accident from any accident previously evaluated.
Clarifying Surveillance Requirement 4.3.4.2.d eliminates f
clearly _ unnecessary inspections, and is not -intended to eliminate inspections necessary to achieve the objective of this surveillance requirement.
This clarification does not change the design, operation, or failure modes of the valves and other components in the turbine overspeed protection system.
Therefore, the proposed change does not create the possibility of a new or different kind of accident'from any.
accident _previously evaluated.
The reheat stop and intercept valve; inspection interval extension does not change the design,-operation, or failure modes of the. valves and other components in the turbine overspeed' protection system.
Therefore, the proposed change does not create the possibility of a.new or different kind of accident from any accident previously evaluated.
3.
Does the change involve a significant reduction in a' margin; of safety?
The _ accident of interest'is a destructive turbine overspeed event.
The probability of turbine overspeed with an-extended (18 month) test interval. for reheat stop-and intercept -valves has been determined to;be within applicable acceptance criteria.
The change.does not affect the' design, operation, or failure modes; of the ~ valves or-other compot;ents in the turbine overspeed protection ' system.-
Therefoce, this proposed change
_does -not-involve 1 a significant reduction in a-margin of safety.
Changing "stop valve" to read
" throttle valve" and-"high pressure turbine reheat stop valves" to read " low pressure.
turbine reheat stop valves" is editorial in-nature, and does not change the design,- operation, or._' failure _ modes ofuthe valves
'or other components in the turbine overspeed
. protection system.
.Therefore, the proposed _ changes.do1not involve a significant reduction in a margin of safety.
clarifying surveillance Requirement 4.3.4.2.d is intendedito eliminate _
clearly unnecessary inspections,. and.-is not intended to-eliminate inspections necessary to achieve.the-objective of this surveillance requirement.
This clarification does not change the
- design, operating parameters, or failure modes of the valves' and other components in the turbine overspeed protection system.
Therefore, this proposed change-does not involve.
a-significant reduction in a margin-of safety.
4 ATTACHMtNT B,_ continued
-ProposedLTechnical. Specification ChangeLNo. 16, Revision 1 Page 8 The reheat stop and intercept valve inspection interval extension does~ 'not change the design, operating parameters,-
or failure modes of the valves and other components lin.the turbine overspeed protection system.
This inspection-interval extension was also considered in the calculation of turbine missile ejection probability mentioned-previously._
It was determined that the probability of turbine missile ejection is-within applicable acceptance criteria.
Therefore, the proposed change does not involve-a significant reduction in a margin of safety.
F.
NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Based on the considerations expressed above, it is concluded that the activities associated with this license amendment request satisfies the no significant hazards consideration standards of 10 CFR 50.92(c).
Accordingly, a
no significant hazards consideration finding is justified.
G.
UPDATFD FINAL SAFETY ANALYSIS REPORT CHANGES Changes to the Unit 2 UFSAR are provided in Attachment D.
UFSAR' Sections 3.5 and 10.2 will be revised after the technical specification changes discussed in this submittal are approved.
Backcround Information Two electronic turbine overspeed trips were_ originally provided.
The first-trip circuit includes a speed pickup at the turbine stub shaft and provides a signal to the emergency. trip cabinet at 111.5 percent turbine overspeed.
This' trip circuit does not have
. provisions for on-line-testing without tripping the. turbine.
The second trip circuit-includes a speed pickup at the turning
_ gear and provides a' signal to the overspeed trip chassisJwithin the emergency, trip cabinet.
This trip. circuit would initiate a turbine trip at 111 percent turbine overspeed and.provides for on-line testing without tripping the turbine. -However,.the trip:
circuit was found'to beiunreliable due to an undeterminedLsource:
of
" noise" that interferes-with the signal going t-o the'overspeed L
trip chassis,. This trip was initially disabled-and later_ removed-by DCP 1152 (Reference 2).
UFSAR Chance Description Page 3.5-9 will be revised by. adding a description.of the tursine i
missile ejection probability-calculation results.
Page 3.5-23 will be revi 41 by = adding references to lthe calculation of turbine i s 3
ejection probability, and the i
letter. from 'Duquesne LigCL Company to the Nuclear Regulatory Commission that forwarded tne calculation.
Page 10.2-5
'will be revised to. delete reference to complete on-linez testability since the 111 percent trip has been removed.
y
i
_AT'fACHMENT B,' continued Proposed Technical Specification Change No. 16, Revision 1 Page 9 Page 10.2-8 will be revised to indicate that high pressure turbine valves are exercised according-to _ technical specifications.
The sentence that describes testing ofL mechanical and backup turbine overspeed trips also will be-revised.
Reference to the removed backup turbine overspeed. trip-will be de'leted.
This sentence also will be--revised to indicate that a
mechanical overspeed trip test is performed during start-up.
Page-10.2-13 will be revised to indicate that functional testing-of the turbine steam inlet valves will be performed according to technical specifications.
I.
REFERENCES 1.
Letter from J.
D.
Sieber (Duquesne Light Company) to.the NRC dated May 28, 1992.
Subject-Turbine Valve Surveillance Testing (TAC M77640).
2.
Design Change Package (DCP)
- 1152,
" Turbine-Trip. System-Modification."
A summary of the safety evaluation for this DCP was submitted _to-the NRC in accordance with 10 CFR 50.59 as part of the 1989 Report of Facility Changes, Tests and Experiments, pages 75 and 76, (May 23, 1990).
?
3 ATTACHMENT C
-l Beaver Valley Power Station, Unit No. 2 Proposed Technical Specification Change No. 16, Revision 1 REPLACEMENT PAGES Typed Pages:
3/4 3-74 3/4 3-75 f
l:
4
-NPF-732
-INSTRUMENTATIOH-iTJQBRIJE OVERSPEED PROTECTION-LIMITING CONDITION FOR OPERATION e
3.3.4 At least one Turbine Overspeed-Protection System shall be
~
APPLICABILITX:
MODES 1, 2*,
and 3*.
ACTIQH:
a.
With one throttle-valve or one governor valve'per high'l pressure turbine steam line inoperable and/or-iwith'one:
reheat stop valve or one reheat intercept valve'per low-pressure turbine steam line inoperable, restore the-inoperable valve (s) to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />,--.or close at least one valve in the affected steam-line(s) or_
isolate the turbine from the steam supply within the next'6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
b.
With the above required Turbine Overspeed Protection _ System:
otherwise inoperable, within 6' hours isolate'the turbine from the steam' supply, The provisions of Specification 3.0.4 are not' applicable.
c.
SURVEILLANCE REQUIREMEl:TS 4.3.4.1 The provisions of Specification 4.0.4 are not' applicable.
4'.3.4.2 The.above required Turbine-Overspeed ' Protection. System-
-shall be demonstrated OPERABLE:
a.
By. cycling.each of the following ' valves 'through~ at least1l
~
_one complete cycle from the running position:
1)
Four high pressure turbine throttle valves at-least once per_31_ days, l
-2 )
Four high. pressure turbine-governor valves at least-once per 31 days,
.3).
Four low. presst.re turbine reheat - stop valves at least-once per 18 months, 4)
Four low ~ pressure turbine-reheat. intercept valves at least once per 18 months, Specification not applicable with'all main steam isolation valves.
and associated-bypass valves in the closed position and all other:
steamLflow paths to'the turbine isolated.
BEAVER VALLEY - UNIT 2 3/4 3-74 Amendment No.
Proposed
-NPF-73 i
- INSTRUMENTATIOH; SURVEILLANCEFREQUIREMENTS (Continued) b.
By direct 1--observationE'of "the. movement of each of the following
' valves through-one-. complete cycle from the running position:
1)
Four high pressure turbine throttle valves at least once per 31-days, 2)
Four high pressure turbine. governor valves at least
~
once per 31 days, 3)
Four low pressure turbine reheat.stop 'alvesfat--least v
once per 18 months, 4)
Four_ low pressure turbine reheat. intercept valves-at least once per 18' months,
- c. At least once per 18 months by -performing a
CHANNEL CALIBRATION on the turbine-overspeed protection' systems, and
- d. At -least-_once sper 40 months by disassembling at-least one-of each-of-the: above valves-and performing.a_ visual andy surface inspection-of valve seats, disks,-
and-stems _and.
verifying no unacceptable flaws or excessive: corrosion., If unacceptable flaws or excessive corrosion are-found, all:
other valves: aaf that type-shall-be inspected unless the
-nature of the problem can: be _directly_lattributedito:a:
-service condition:-_ specific-to that valve. JFor-_ reheat =stop and -intercept valves _the-inspection-cycle may beLincreased to a maximum of 60 months, provided therefis no indication _
of operational distress.
r l
l i
BEAVER VALLEY - UNIT 2 3/4 3-75 Amendment No.
Proposed t
l=
t ATTACHMENT D:
~ Beaver Valley Power Station,. Unit'No. 2
')
Prop'., sed'Tochnical Specification Change No. 16, Revision ^l' APPLICABLE UFSAR CHANGES-d Section 3.5 Pages 3.5-9, and -23 Section 10.2 Pages 10.2-5,
-8, and -13 L
1 4
h 4
A
- - ~. - - - - - - -. - -. - - - - - - - - -
BVPS-2 LTSAR 3.5.1.3.4 Probability Evaluation The probability of unacceptable damage to safety-related structures, systems and components by turbine disk fragments is less than the plant safety objective of 10' per year.
This is accomplished by a sufficient'ly frequent turbine testing and inspection schedule which provides that the probability of turbine missile generation (P1) is maintained at 10' per year or less.
The combined probability of strike and damage (P2 P3) is considered
-2 to be 10 per year or less.
This conservatively considers the unfavorable orientation of the turbine generator.
Table 3.5-11 provides a correlation between P1 and years of operation since the last disk inspection.
The P1 values are for the total plant considering all rotors and both design and overspeed conditiens.
The turbine testing and inspection program is provided in Section 10.2.
INSERT 1 ----->
3.5.1.3.5 Turbine Overspeed Protection The turbine speed control system has adequate redundancy to ensure that the turbine does not attain destructive overspeed.
The standard Vestinghouse analog electro-hydraulic control (EHC) system and electromechanical trip system includes three separate speed sensors mounted on the turbine stub shaft-located in the turbine front pedestal. These sensors are:
1.
Mechanical overspeed trip weight (spring-loaded bolt),
2.
Electromagnetic pickup for main speed governing channel, and-3.
Electromagnetic pickup for the overspeed protection control channel. This pickup uses the same toothed wheel-as item 2.
An overspeed protection controller is provided and is activated in the event turbine speed exceeds 103 percent of rated speed (1,800 rpm), or the measured electrical output of the generator as compared to the low pressure turbine inlet pressure indicates a power mismatch (load impulse pressure feedback).
The low pressure turbine inlet pressure represents the energy input to the turbine generator.
If a mismatch occurs, one of the following actions is initiated:
1.
During a partial load drop the interceptor valves are closed and then reopened after a set time delay, or 2.
During a full load drop, both the governor and the interceptor valves close. The governor valves remain closed until the speed is decreased to rated speed (1,800 rpm).
The interceptor valves are modulated and reopen when speed decreases to below 103 percent of rated speed to remove 3.5-9
1 4
INSERT l' The following paragraph is to be inserted at the end of-Section 3.5.1.3.4 on Page 3.5-9.
A calculation was performed to determine the. turbine missile ejection probability -resulting from an1 extension-of reheat stop-and intercept valve test intervals.
A' reheat stop andLintercept
~
valve inspection interval of 60- months -was assumed in-the i
calculation.
Based on the calculation,.it was determined.that' the total turbine missile generation.
probability meets-applicable. acceptance criteria with an-18 month reheat-stop and.
- intercept valve test. interval.
y.
4 BVPS-2 UFSAR' Transportation S'fety Board 1972.
Railroad-Accident Report National a
for East St. Louis,,Ill.
No. NTSB RAR-73-1~.
National Transportation Safety Board 1974 Railroad' Accident Report for Houston, Tex. No. NTSB-RAR-75-7.
National. Transportation Safety Board 1979.
Railroad Accident Report.
~,
for Muldraugh,-Ky. No.-NTSB.-RAR-81-1.
l National Transportation Safety Board 1980.- Railroad Accident Report for.Crestview, Fla. No. NTSB-RAR-79-11.
- Rhoads, R.E.
1978.
An Assessment of the. Risk of Transporting Gasoline by Truck.
PNL-2133, Pacific Northwest Laboratory, Battellei Memorial Institute, Richland, Wash.
- Siewert, R.D.
1972.
Evacuation Areas.for Transportation Accidents Involving Propellant Tank Pressure Bursts.
NASA' Technical Memorandum a
Y68277.
- Sihweil,
-I.
'1976.
.SEB Interim Position on-Ductility' Ratios:of
~
Reinforced Concrete -_ Structural Elements.
Memorandum,= -USNRC, (SEB:808).
Stone. & Webster Engineering Corporation - (SWEC) 1977.
Barrier Interaction,' Topical Report SWECO-7703.-
. Missile _-
U.S.
-Nuclear = Regulatory Commission. (USNRC) 1981.
Standard Review-Plan for the Review of Safety Analysis Report for. Nuclear Power Plants. - Barrier Design Procedures'. Revision'1,- NUREG-0800.
.U.S. Department of. Transportation (USDOT) 1981a'(Research and_Special Programs: Administration)',
. < Incidents. Involving. Deaths. Inj uries ', ;-
Damages Greater than' $50,000 or' Evacuations.. Computer printout,:
-i periods covering-12/22/70 to 9/5/80,- Washington,: D.C.
U.S.
Department.~ofl Transportation' (USDOT)- 1981ti.
Research ~and' I
Special Programs: Administration).
. Incidents. Involving Fire. and -
Explosions _ by'. Rail.
Computer printout,-periods. covering,6/6/73 to-
- 11/1/80,1--Washington, D.C.
Westinghousa-' Electric Corporation November 1986.. Power-Generation -
Operating' Division. Turbine Missile Report,. CT-25266, Revis' ion :0, Results:- ofL Probability Analysis of:: Disc Rupture -and. Missile 1 Generation for the~ Beaver. Valley Partially Integral Rotors.
Westinghouse Electric Corporation April 1992. Calculation of Turbine Missile Ejection Probability Resulting From Extending The Test Intervals OfInterceptor -
o And Reheat Stop Valves At Beaver Valley Units 1 and 2.'
Sicher J. D., May 28,1992.: Turbine Valve Surveillance Testing. Letter, Duquesne Light Company to the Nuclear Regulatory Commission (ND2NSM:5568).
3.5-23
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4 BVPS-2 UFSAR The control of the reactor-and TG is accomplished from the main control room, which contains all instrumentation and control equipment required. The control system allows BVPS-2 to accept step load increases of 10 percent and ramp load increases of 5 percent / min over a load range of 15 to 100 percent power.
Below 70 percent full power, the unit can accept a turbine trip without initiating a reactor t r i'p.
Turbine bypass and atmospheric steam dump capacity permits 85 to 100 percent external load rejection without a turbine or reactor trip. The control of the reactor with turbine is covered more fully in Section 7.7.
The turbine bypass system's capability is covered more fully in Section 10.4.4.
The Westinghouse analog EHC system and electro-mechanical trip system on the turbine stub include three separate speed sensors, mounted shaft located in the turbine front pedestal as follows:
1.
Mechanical overspeed trip weight (spring-loaded),
- 2..
F.lectro-magnetic pickup for main speed governing channel, and 3.
Electro-magnetic pickup for overspeed protection control channel.
(This pickup uses the s ame toothed wheel as item 2.)
10.2.2.1.2 Turbine Trip System The electro-hydraulic emergency trip system consists of an emergency trip block, two test blocks mounted on the governor pedestal, a cabinet containing all the electrical and electronic hardware, a remote trip test p anel, and main control board-mounted. trip pushbuttons for manual tripping. The emergency trip system offers a redundant overspeed protection (Section 10.2.2.1.3) via electro-hydraulic and mechanically-actuated systems, an auto stop trip (AST) system which monitors various TG parameters, an overspeed
-?
5 protection controller (OPC) which monitors turbine speed and load, and a mechanical overspeed trip weight.
The system also offers
-pa rt ici ::rline t::tchility, provisions for detection and diagnosis l
of failed devices, and provisions for inservice maintenance and inspection.
Under normal conditions, the AST solenoid valves and the interface diaphram valve are closed, blocking the path to drain off the auto-stop emergency trip header fluid. The pressure in the trip header line keeps the dump valves associated with each steam valve closed.
Upon collapse of this pressure, the dump valve will unseat, causing the. throttle valves, governor valves, intercept valves, and reheat stop valves to close in approximately 150 milliseconds.
The AST solenoid valves are separated into two channels,.with two valves per channel, which are kept energized from separate relay trains in the emergency trip system cabinet.
If a trip contingency 10.2-5
4
.BVPS-2 UFSAR The steam to the high pressure-glands is maintained-at 5 psig.
Steam to the low pressure glands:Is maintained at 1 psig.
Any excess steam is bypassed-to the' condenser through a spillover valve. The turbine gland sealing system is described more fully in Section 10.4.3.
10.2.2.3 Inspection and Testing Requirements -
The main turbine stop and control valves and the combined interceptL and intermediate stop valves-are exercised renthly in accordance with-
'-*' ens to detect possible valve stem sticking.
e__.,_t..--
/3The valves are-closed and_ then reopened during this procedure.
Mechanical :nd 52:hu; overspeed trip tests are performed pericdi;;11y... K
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2.....
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....s.
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Technical Specifications 10.2.2.4 Generator during startup The generator is sized. to accept the output of the turbine. The generator is equipped with an excitation system.
hydrogen control system (HCS),
and a seal oil. system. -The generator terminals are connected to the main step up-transformer and unit ' station - service transformers through the isolated phase generator leads.
The air-cooled generator excitation system controls ' the voltage of the generator.
The HCS includes pressure regulators, _ condition monitor for detection' of thermally produced particulate, purity monitor for recording changes in gas density, temperature. pressure transmitters, liquid detector, and water-cooled gas coolers.
A circuit to supply and control the CO:
is used during filling and purging. operations to avoid explosive gas mixtures. :A hydrogen seal oil system (Figure 10.2-9) prevents hydrogen leakage or air inleakage-through the generator shaft seals.. This system includes pumps,
~
controls, and a storage -tank, and degasifies the oil before it is returned to - the shaft seals.
10.2.2.5 Generator Hydrogen The HCS is used to cool both the rotor and stator. The rating ofLthe generator is a-function of-the hydrogen pressure - which is normally 75 psig.
The system includes' pressure regulators for control of the hydrogen gas, and a circuit for supplying and controlling the carbon:
dioxide _ used ini purging the ' generator du, ring filling and. degassing :
operations. To prevent-hydrogen leakage through the generator shaft-seals, a hydrogen. seal; oil system is provided. This system, which--
' includes pumps,? controls, and-a storage tank, 'deaerates; the' oil-before it is sent to-the shaft seals.1The hydrogen control system appears on Figure:10.2-10.
Hydrogen is_, manually fed ?to the generator to maintain design-pressure..A normally. closed automatic shutoff valve, provided at the bulk storage
.f acility,- is operable from the local hydrogen contro11 panel. The bulk storage facility also supplies hydrogen to the:
10.2-8
-vt
BVPS-2 UFSAR The ISI program for throttle, governor, reheat stop and interceptor valves is in accordance with vendor recommendation of 15, 27, and 39 months after initial start-up of a turbine.
In this program, some valves are inspected 12 to 15 months after start up, others 24 to 27 months, and the remainder 36 to 39 months so that all valves are inspected at least once in the 39 months of operation following initial start-up.
Throttle and reheat stop valves are inspected twice in this period.
After this initial inspection program is completed, valves will be inspected periodically in accordance with Westinghouse recommendations in accordance with Technical Specifications.
g Ae 4unctional e turbine steam inlet valves will be performed renthly.k'Thi; t::t :
b ::de while the unit is carrying load.
The purpose of the testSis to ensure proper operation of the
- throttle, governor, reheat stop, and interceptor valves.
The operation of these valves will be observed during the test 5by an l
operator stationed at the valves.
Movements of the valves should be smooth and free.
Jerky or_interm tent motion may indicate a buildup of deposits 'n shafts.-
These tests can be performed 10.2.3.6 High Temperature Properties The operating temperatures of the high pressure r. tors in turbines operating with-light-water-reactors are below the creep rupture range.
Creep rupture is, therefore, not considered to be a factor in assuring rotor integrity over the lifetime of the turbines.
10.2.4 Safety Evaluation Beaver Valley Power Station - Unit 2 is a pressurized water reactor.
As such, during normal operation the concentration of radioactive contaminants is minimal and no shielding is required for the TG, thus permitting unlimited access.
There is no QA Category I equipment in the turbine building,
- thus, rupturing of the connection-joints
~
i.
between the low pressure casing and the condenser will not adversely affect any QA Category I equipment.
The turbine stop and control valves and reheat stop and intercepe valves are arranged such that failure of any one valve will not.cause an overspeed event.
10.2.3 References for Section 10.2 Westinghouse Electric Corporation 1971.
Scientific Paper.
71 - 1E 7 -MS LRF-Pl.
MSTG-1P.
10.2-13
_