ML20030D916
| ML20030D916 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/01/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20030D910 | List: |
| References | |
| REF-10CFR9.7, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-2.B.3, TASK-2.F.1, TASK-2.F.2, TASK-TM NUDOCS 8109170149 | |
| Download: ML20030D916 (19) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOG A. TENNESSEE 374o1 400 Chestnut Street Tower II September 1, 1981 Director of Nuclear Reactor Regulation
- - Attention:
Ms. E. Adensa=, Chier Licensing Branch No. 4 Division of Licensing U.S. Nuclear Regulatory.Com=ission Wa.shington, DO 20555
Dear Ms. Adensa=:
In'the Matter of
)
Docket No. 50-328 Tennesser. Valley Authority
)
As a result of our meeting with the NEC staff on August 25, 1981, T7A was
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requested to provide additional information on TVA's proposed i=plementa-tion changes for the following NRC requirements relatec to Sequoyah Nuclear Plant unit 2.
j (1) Permanent Hydrogen Mitigation System (2) Reactor Coolant System Vent System (3) incere Thermocouples (4) ? Technical Support Center (5) Post' Accident Sa6pling (6) Accident' Monitoring Instrumentation
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Enclosed is the requested infoE=ation.
We have provided detailed design and procurement schedular information,
_.. justifications for interi= operation, and reasons for schedule revisions.
In all cases, we believe' ' alternate neasures are provided to ensure safe plant, operation until these codifications can be !=plemented.
If you ha've any questions, please get in touch with D. L. Lambert at FTS 8.57-2581.
Very truly yours','
TrhTESSEE VALLEY AU HORITY
.. Mills, ag r u.
l Nuclear Regulation and' Safety Sworn p and subscr bed before me this. / M day of &.fk 1981 7
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Netary. uclic 2
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Enclosu-8109170149 810908 PDR 10CFR r
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i ENCLOSURE SE000!AE NUCLEAR PLANT SCHEDULE REVISIONS FOR (1)
PERMANE!U ETDROGEN MITIGATION SY, STEM (2)
REACTOR' COOLANT SYSTEM VENT SYSTEM 1
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(3)
INCORE THERMOCOUPLES (4)
TECENIb1 SUPPORT CENTER (5)
POS7 ACCIDENT SA!9 LING (6)
ACCIDENT MONITORING INSTRU.UICATION O
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PERMANENT hTDROGEN MITIGATION SYSTEM (FEMS)
Descriction of Chahre Recuested TVA is proceeding to i=plement a Permanent Hydrogen Mitigation Syste:
(PEMS) at Sequcyah Nuclear Plant units 1 and 2 to satinfy license condition 22.D(2) for unit 1 and 22.g(1) for unit'2. These conditions require that "for operation of the facility beyond January 31, 1982, the Cc==ission =ust ecnfir: that an adequate hydrogen control syste: for the plant is installed and will perfor= its intended function in a =anner that provides adequate safety'=argins." The PEMS is designed to ensure centro 11ed co=bustion of lean =ixtures of hydrogen using ther=al igniters distributed throughout centainment and is intended to ce=pletely replace the installed Interi:
Distributed Ignition Syste: (IDIS), which was designed to cperate en the sa=e principle. While replacing the IDIS with the PEMS, TVA intends to upgrade the system by i= proving the quality of co=ponents, adding redundancy, and enhancing the control capability.
However, because of the
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lead ti=e required.to procure the system co=ponents and the adequacy of the si=ilar IDIS that is already operational, TVA requests that i=plementation of the PEMS be deferred until the first refueling outage for each unit; The current schedules fer those outages are Septe=be1982 for unit 1 and January 1983 fer unit 2.
This request'has been made pre':iously to the NRC sta'r (reference letters from L.
M'. Mills to A. Schwencer dated March 10, j
1981, and L. M. Mills to I. 'Adensa= dated July 1, 1981).
It should be noted that TVA's request for extension is for hardware i=plementation onfy' and'is not related to the research progra= which should be concluded and substantially documented,by January 31, 1982.
Design and Procurement Infer =ation
' The' design of the PEMS-is. essentally ce=plete, and procurement of the new This includes environmentally and seis=ically equip ent has begun.
qualified electrical transfer =ers, distribution panels, cables, and control.
The lead times, even under emergency purchase, are such that switches.
1982.
delivery of all the co=penents cannot be prc=ised before June 1, Specifically, the igniteps are scheduled for delivery by January 1,1982, l
the transformers by March 1, 1982, and the distribution panels and switches 1982.
TVA has decided to specify the highest practical syste=
by June.1, and.cc=ponent standards for the PEMS rather than to relax the standards in l
crder to erpedite delivery.
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I Justi.ficatien for'Lencth of Outace The installation of the PEMS inside containment will require extended periods of occupancy in both upper and lower ec=partments during a New cable and conduit =ust be routed for each of the 60 new shutdown.
Current igniter locations and new igniter asse=blies must be =ounted.
caterial esti=ates for this syste= include 20,000 feet of cable, 3500 feet cf conduit,.350 supports, 60 junction boxes, and 120 cable tsr=inations.
By the nature of the igniter locations being distributed throughout the centainnent area and generally at the. top of each volu=e, physical access for installation of the system is difficult.
As a result, te=pora:y scaffolding will be required for most of the work..In addition, the f
ecstain:ent acc22: restrictions applicable during shutdown of a unit that has been in operation conplicate the work schedule.
TVA esticates that 37,000 =an-hours will be required to install the entire syste:. Much of this werk will be inside containment.
Even assuming that the work is done during the first refueling outage and. progresses 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> a day for 10-12 weeks, it is still the critical path item fer.a plant cutage of 110 uays.
Therefere, the shutdown necessary to install the centainment pertion of the
?EP3 cust be deferred until the first refueling outage for each unit to avoid a separate and lengthy forced outage.
interi: Measures TVA believes 'that the extensien to the first refueling outage is acceptable and reascnable fer a nu=ber of reasons, of which two are s"--=*ized here.
First, there would be no real 1:provement over the IDIS if syste=
installation was rudhed before qualified replacement ec=ponents could be obtained.
Second, the i= pact of the extension en overall risk to the public is negligible because the event to be citigated is unlikely, the duration of the extension is only a s=all fraction of the plant operating life, and t.be IDIS should be almost as reliable a citigation systen as the PEMS.
The IDIS operates en the same concept as the PEMS, has the same functienal capability, has equivalent coverage by locatien, has si=ilar
=anual initiatien logic, and has diesel backup power. TVA believes that
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the IDIS will continue to serve as an " adequate hydrogen control syste=?
until the PEMS can be installed.
St==arv TVA is proceeding to replace the present Interi= Distributed Ignition System with the Permanent Hydrogen Mitigation System in both Sequoyah units.
However, since all of the qualified equipment cannot be procured and delivered until tid-1982 ahd a separate forced plant outage for system installation would be quite lengthy, TVA requests that the license concitien be modified to allow installation to be cc=pleted during the first refueling outage for 'each unit.
In the meantime, TVA believes that the Interi= Distributed Igniti-en System that is installed and operational in both units provides fully adequate safety cargins to citigate the effects of hydrogen released during.a degraded core event.
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REACTOR C00LANI SYSTEM VENIING NUREG-0737, ITEM II.B.1
Background
In response te NUREG-0578 and a reco=mendation frc= a TVA internal study group en the TMI accident, TVA signed a contract with Westinghouse in December 1979 for, the ' addition of a reactor pressure vessel (RPV) head, vent.
The syste: for Sequoyah unit 2 was to be delivered by Septe=ber 1,1981.
TVA furnished NRC details of the conceptual designs for the RFV and pressurizer vents en July 1, 1981 (as required by NUREG-0737).
TVA's January 1980.. sponse to the NRC on NUREG-0578 cc:=:itted to the addition of the RPV vent and stated that pressurizer venting is already included in the Sequoyah design.
Since the Sequoych design contained two pcwer-operated relief valves (PORV), either of which could accomplish venting, the pressurizer vent design was considered to be adequate.
In October 1980, NUREG-0737 gave additional details on, the vent system.
Although The RPV vent syste= wc.s deter =ined to meet the NUREG-0737 requirements, the PORV's for the pressurizer vent appeared to be deficient j
in the areas of environments.1 qualification and operability following an earthquake.
Subsequently, a M contacted Westinghouse in Nove:ber 1980 regarding a pressurizer vent-system which meets the requirements of NUREG-0737. Westinghouse has furnished TVA in May 1981 with a conceptual design, but a centract has not been signed for delivery of the syste=. TV1 is pursuing this issue with 'the intent of'having all design and procurement functions ce=pleted by July 1, 1982.
However, due to the preliminary.
status of this design, the work inside conta$r:cnt required to install this system cannot be co=pleted before full power operation of unit 2.
Ecui: ent Procure:ent With the exceptien of tdo valves, all the Westinghouse equip =ent for the RPV vent has been delivered.
In approxi=ately two more conths equipme,nt There is delivery,.fiping supports, and other drawings should be co=plete.
a ' hand indicator controller for the cain control room which is to be procured by TVA.
At.te= pts by TVA to obtain this ssitch has resulted in no resp'ense.from the venders.
This lack of response is due to the require-sents that the switch has to be qualified id accordance Uith IEEE Standard l
325, 1974 versien.
However, based on recent NRO staff infor=ation on the i
NU?.EG-05BB require ents for equip =ent in "=ild" environments, TVA intends to obtain a seis=ically qualified suitch and to deter =ine that it has proper environmental qualification.
TVA's plan has been to have the RPY vent syste= ready for installation before July 1982. We still believe that this schedule can be =et.
Interim Measures The schedule for the pressurizer vent installation is also July 1982.
However, as discussed above, this schedule is not as firm as for the RPV vent because of the lack of.a contract at this time.. As noted in our response to NUREG-0578, there already exists a capability for venting of l
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design provides sufficTent interi:
capability for venting t.e presst, ze, Su =a v 3asically, TVA's need for an extension on the schedule ' < p1enentatien date of reactor coolant syste~ vea*4 outage tsquired to implement this modification.-.ng.4s to.he purpose
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, seeks in cold shutdown, not including time for shutdown and sta*'upThree +o fo,u be required to cc:;1ete the installation of the vent syste=.
v4' have to be depressurined and cooled *down to allow for insta
~VA reco=nends that the Sequoyah unit 2 full power operating license be 4 ollowing the first refueling.conde.icned.o requi: e installation of the RC g
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If; CORE THEFy.0000PLES The following is WA's response to NUREG-0737, ite: II.F.2, attachment 1,
" Design and Qualification Criteria for Pressurized - Water Reacter Incore Ther=occuples," and NUREG-0578, ite: 2.1 3(b), sane subject.
Points are addressed in the sa=e order as given in attach =ent 1 to ite: II.F.2.
,,, Firse,.7TA's incere ther=occuple syste= us upgraded since the TMI-2 event will be described.-
1.
The 'Sequoyah incere thermocouples are located at the core exit for each quadrant, and in conjunction with core inlet RTD data, are sufficient to provide indication of rar.a1 distribution of the coolant enthalpy rise across representative sections of the core.
Sixteen (four per quadrant) of the core-exit thermocouples will be designated as PAM sensors.
2.
The pri=ary operator display is a co=puter-driven printer. This system has the following capabilities:
A spatially oriented core =ap is available on de=and which a.
indicates the te=perature at each core exit ther=occuple location.
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b.
An exa=ple of the Seciuoyah selective readings is an on-de=and tabular listing of all instantaneous incere ther=occuple *alues.
A printout of average, instantaneous and =axi=u values is 'provided c.
Tror all T/C te...peratures.
The. range vill =eet the suggested range in the RG.(200 F to 2300 F).
d.
Trend capability. showing te=perature ti=e histories is designed into the syste=.
Strip chart recorder pof nts are available to assign to 27y incere ther=occuple en de=and.
In addition, a point value trend printout is available on the control roo= printer.
Alar =capabilithisprovidedinconjunctionwiththesubcooling e.
=enitor which uses the average of all the T/C readings in the.
calculations.
f.
The control-roo= displays are designed for rapid operator access and ea'se of viewing data.
Also, the incere progra= has a
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validity-check co=parison whien reduces the probability of access-ing false readings.
3 A backup analog readout is provided with the capability of selee;ive The range cf the syste= is 0-700'F.
reading of any T/C in the syste=.
Another =eans of obtaining this data is by reading the raw signals (T/C and reference ";nction output) with portable test equip =ent.
This data is available in the control' building and would be accessible under all conditions should the pri=ary and backup display devices fail.
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Prasant isolation between th2 primary and backup channels is t.
i=plemented in the for= of electrical switches. The pri=ary and bacsup display _* channels are powered by a reliable battery-backed oower source.
The existing incore T/C system is a very si=ple set of hardware which 5.
should, by virtue of its si=plicity, be,a highly reliable and accessible system.
Although IVA has been required through the licensing proc sss to co==it to the environ = ental qualification and the physical sepa-s'acn of these 16 incere ther=occuples, we believe further enhancement of the inecas ther:occuple syste= will not add ta overall plant safety.
In addition to the incere thermocouples, TVA utilizes a satura tion =eter to detect / follow the approach to inadequate core cooling and expects to utilize the reactor vessel level instrument to deter =ine the degree of inadequate core cooling.
'The Reactor Vessel Level instrument is designed to provide' direct readings This Reactor Vessel of vessel level which can be used by the operator.
Level Instrumentation System does not replace existing syste=s and is not coupled to safety syste=s, but acts on1.y to provide additional infor=ation to the operator.
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Th,e Upper Range Reactor Vessel Level Instrumentation has differential The pressure measurement across the upper region of the reactor vessel.
system utilizes two diffe'rential pressure cells measuring the pressure drop The fro =,the reactor coolant.hotleg piping to,the reactor vessel head.
system provides an indication of reactor vessel water level above the'.
hotleg pipe when the pu=p.in the loop with the hotics connection is not The nu=ber of pu=ps operating in the other loops has an effect operating.
of less than 10 pere'ent of this indication. When the pu=p is operating in the loop with the hotleg connection, the instrument reading will be offscale.
The narrow range reactor vessel level instrumentation =easures vessel leveS
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fro = the top to the bottom of the reactor vessel when only one or no The instrument will also measure the reactor coolant pu=ps are running.
reactor core and internals pressure drop, and therefore an indication of l-
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the relative void content er density of the circulating fluid wh pump is operatin's.
be offscale.
l The wide range reactor vessel level instrument =easures the reactor core internals and outlet pressure drop for any co=bination of pu=ps running.
Cc=parison of any =easures pressure drop with the measured pressure drc during ner=al operation will provide an approxi= ate indication of the relative void content or densi.ty of the circulating fluid..
t te=perature Ao provide the re-uired accuracy for water level =easure=en,
measurements of the reference legs are provided.
Their measuraments together with the reactor coolant te=perature j
measurements are used to co=pensate the differential pressure particularly during the environment inside the contain=ent structure following an accidenu.
03e Reneter Voss*1 Lcrea Instrumentation Systa= utilinas differential pressure cell instru=entation in two of the hotleg pipes. The instru=ented hotleg piping will nof be adjacent, but with respect to the plant layout, will be en opposite sides of the reactor vessel.
The differential pressure cells are to be located outside of containment so that calibration cell replacement, reference les checks and fillingr and operation are made more easily and the overall system accuracy is improved.
- - Instrumentatien for the operator for the Reactor Vessel Level Instrumentation' System is intended to be unambiguous and reliable so that operator error or =isinterpretation is avoided.
Upper range, narrow range, and wide range leve? r.ignals are available froc each train for display on standard VX-252 type vertical scale voltage meters. Thus, the indication is compatible with existing control board layouts.
The indication signals are electrically isolated from.the pr' tection set and are suitable to serve as eitbSr a standard control grade o
or postaccident monitoring output.
The' control board displays provide the following infor=ation:
1 1.
An indication of retctor vessel. level (narrow range) for each instrumented set displaying ves.sel level in percent from 0 to 60
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percent after co=pensation for the effects of the reactor -coolant and capillary line temperature and density, when reactor coolant pumps are
. net operating.
2.
An indication of reactier differential prissure (d/p) (wide range) from eae.i instrumented set, displaying d/p in percent from 0 to 100 percent, aftor co=pensation for the effects of th* reactor coolant and capillary line te=perature and density effects, when reactor coolant pu=ps n' e r
operating.
3 An indication of upper range vessel level on each of the' two i'nstrumented sets displaying vessel level in percent from 60 to 100 percent after ce=pedsation for any reactor coolant and capillary line i
density effects, when the reactor coolant pu=p in the loop with the he'.,eg connection is not operating.
A status light will indicate *the operation of the reactor coolant pump with the.hotleg connection.
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- Eedundant displays are provided for the two sets.
Level 'information based on all three d/p measurements is presented.
Ocrrection for reference leg densities is automatic.
Any error cond,itions such as
' out-of-range sensors or hydraulic isolators are autecatically displayed on the affected ceasurements.
The Reactor Vessel Level Instrumentation is to be used in conjunction with a coolant subcooling readout to deter =ine the state and transient behavior of the reactor coolant syste=.
The reactor vessel wide range i
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level indication will read onscale with all four reactor coolant pu=ps-running during nor=al operation from 0 to 100 percent full power. With l
all pumps shut down, t,he indicator
- will provide, a direct indication of I
water level in the reactor vessel.
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TVA believes that the combination of saturation ~aete*
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oco.:ples w,h extended range provides more than adequate info :.a** o-o detec. and determine the degree of inadequate core cooling.
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. _posee requ rements such as incere thermocouple qualification ssary based on the other infor=ation that will be available to ne Su==a v TVE believes that further upgrade of incore thermocouples at Sequoyny unas 2 shou d not be required.
If NRC continues to require further upgradd g
-. cre hermoccuples at Sequoyan unit 2, the full powe epe 3-<n
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be conditioned to require upgradin$ of the incore thermocouples ero startup following the first refueling outage.
Allowing TVA to implemen' the.hermocouple upgrade at the first refuelirs cutage should provide adequate time to prevent significant i= pact on more i=portant work.
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TECHNICAL SUPPOr CEhTER
Background
TVA's letter to NRC dated July 2,1981 (L. M. 4 tills to E. R. Denton) provided the conceptual design for the Sequoyah Technical Suppoht Center I.
(TSC) and other E:ergency Response Facilities (ERF). The letter identified
~ ~ the TSC as the only EEF.that.could not be co=pleted before the October 1, 1982 deadline.
Desien and Procurement The design work for the TSC began with the issuance of NRC Generic Letter 81-10 in February of 1981. At this time, the ec=pletion of the design drawings and the delivery of all ec=ponents to the site is scheduled for Ap'sil 1932.
Outage Time To i=plement the TSC, TVA esti=ates that 60 days of nqnoutage time and weeks of outage time (n;t including.tice for shutdown and startup) will be required.
However, to accommodate plant operating requirements, most of
,I the nonoutage work will extend over a period of about one year.
The outage
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ti=e is required.to allow installation of equipment in the main centrol TVA considers it uns-fe to perfore work of this nature in the = tin.
room.
control room while a unit.is in power operation.
Interin' Heas'ures
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TVA has i=plemented an interi=.TSC as rev'iewed and approved by NRC in Sequoyah SER Supplement'2. The Local Recovery Center and access to ceterological and radiclogical data vill be provided to appropriate respense centers by June 1, 1982. ~TVA's centralized emergency centers have been 'irplemented as ' described in the June 2,1981 letter.
Su==ary TVA reco~== ends that the Sequoyah unit 2 full power cperating license be cenditioned to require ec=pletion of the TSC by July 1, 1983 This will aliew TVA to schedule the necessary outa5e work during a refueling outage.
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POSTACCIDENT S4MPLING NU?sEG-0737, ITEM II.B.3 Introduction i
The overall design and i=plementation of pestaccident sa=pling (PAS) at TVA has gone through =any unforeseen and/or unplanned changes, rany of which 1
- - are due to plant-unique. features.
TVA as a whole has =ade an all-out effort to =eet' cur Janua'ry 1, 1982, i=pl:=entation cate for PAS at Sequoyah kuclear ?lant unit 2.
NUP2G-0737 was issued approxi=ately 1.7 years after the accident at TK! and 1 3 years after the issuance of NU?2G-0576. To =eet the very early date of January lo81 for an operatienal PAS capability set by NU?IG-0575, several normal design activities including a detailed radiation ' dose analysis (both,
airborne radioactivity and ga==a radiation from process equip =ent) were
, bypass ed.
Conservative assu=ptions were =ade and then were used as a basis for the first issues of the PAS design criteria for both Erowns Ferry and Sequoyah Nuclear Plants.
After the schedule relaxation given in NU'2G-0737 occurred, the radiatica calculatiens bypassed earlier,were initiated.
Since the radioche=ical laboratory.and =uch of the auxiliary building at '
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Sequoyah were not originally. designed for postaccident access, the radiation doses that the sampling technicians would encounter enroute to,
the PAS station, to the radioche=ical laboratory, and back to the operational support center were unknown.
Further specifics on how to get' an aliggot of. each sa=pleJfluid into the radioche=ical laboratory instru=entation/ laboratory equipment to get the needed analytical results' were unknown. These are'now believed to be settled.
Once this is done, the radiation doses can be calculated and the needed scope of radiation protecticn clothing and face = asks, etc., are deter =ined, the scope of the
.WAC ceeds can be established.
This work is now in process.
No EVAC needs
. can be finalized until =ission doses are established.
Table I depicts =any other i=portant =ilestones 'for PAS and i=portant date to TVA.
- The following discussions provide specific details on the current status of design and construction, design prob.le=s encountered, and interi= =easures
- available until the PAS is fully operational.
Status of Design and ~ x. m umo..
Although pro'ble=s were encountered with the heating, ven ilation, air-ccnditiening, and air cleanup (HVAC) in the radiochemical"labcratory and sa=ple station, work continued in areas that had a =ini=al chance of being affected by possible design changes. These areas include t'he essential interface services listed below which are required for the operation of the sa=ple statien:
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Co=ponent cooling 2.
Cent. dol air 3
De=iner'alized water li.
Nitrogen 5
Waste dispesal drains l
6.
Shielding 1
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j The design of the above servic2s and their-corresponding piping and valves is essentially ce=plete.
The basic sa=pling ryste: has been purchased fro =
Sentry Equip =ent Corporation and is onsite :.11able for installation.
t Construction has p"ocT ded on the sa=ple station with its presen; status i
listed below:
1.
Cc=pletion is esti=ated between 45 and 50 percent.
2.
All the required shielding (steel and concrete) is in plac'e.
3 The necessary penetratiens for PAS have not been made through the shield walls for the samples.
4.
Additional'pehetrations for -component cooling water through the auxiliary building walls are not. co=plete.
5, The.ork (mostly installation of piping) inside containment has not 4
ec==enced.
It is possible that the sa=ple station could be in the range of 90 percent cc=plete by January 1982.
The items that would not be co=plete_are the
.WAC modifications and the work needed to be performed inside containment.
The proble=s encountered with the EVAC are discussed in the next section.
The design for the modification of the radioche=ical laboratory had been
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placed en hold for a period; therefore, no constructign work has been initiated.
The proble=s faced with.this phase of work are outlined in the next section.
t Design Problems Encountered,
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in an effort to expedite PAS implementation and meet NUREG-0737 requirements for an ensite radiological and che=ical laborato.7, TVA decided to use the existing radioche=ical laboratory as opposed to locating and constructing a new facility.
Although this facility was not originally designed to serve this, function and =ight require some redesign to ens'ure its habitability after a loss-of-coolant accident (LOCA), this appeared to
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be the best possible alternative for meeting NRC requirenents. However,
=cre detailed evaluations regarding the use of this facility have identified the following problems:
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1.
The initial dese and shielding calculations deter =ined that additional l
' shielding is required in the ceiling or reof of the radioche=ical l'ab~ oratory fer personnel protection.
If shielding is added, the l
radiochemical laboratory would likely be shut down during the l
. necessary construction work.
This in t.rn would require a two-unit
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l plant shutdown.
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2.'
Difficulties were encountered in the location and sining of the HVAC and associated ducting for the radioche=ical laboratory.
The proble=s with the sa=ple station HVAC were as fol.iows:
1.
The existing plant auxiliary building gas treatment system which was planned for use in the treatment of the sa=ple station exhaust air could not treat the ' additional flow and, ccncurrently, acco:plish f ta other r3 quired syste= safety functions during,a postulated accident.
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As a recult of ite:
1, a reavaluation of the plant design basis for this syste: 'a.1 r.equired to deter =ine an alternate means of treating the exhaust air.
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These proble=s did not surface all at once. They occurred in a " rippling effect" fro: May th ough July 1981.
The proble=s encountered caused further reevaluation and changes in the syste= design basis.
Readjust =ents
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in the design basis were cc=pleted during August 1981.
T7A is confident
)
~ ~ ~ hat these readjust =ehts. Will essentially resolve the open issues and.at t
the same time meet ind fulfill all NRC require =ents. for PAS.
I!owever, the appropriate dose and shielding calculations remain to be co=pleted in order te confir: the proposed readjustments to this syste=.
Due to design =odificatiens discussed above, changes were required to the IWAC specifications.which added a =ini=u= cf three =enths to our procure =ent schedule.
Currzntly our schedules for procure =ent identify contract award in.Nember 1981 and equip =ent delivery in Septe=ber.1982.
This schedule is based en maxi =um use of e=ergency purchase procedures.
Interi= Solutiens fer PAS Until the PAS syste= beco=es fully operational TVA has written interi I
procedures for obtaining a sa=ple(s'). These procedures are c'escribed in the plant's technical ir.structions (TI-56). These procedures would allow TVA to collect sa=ples from existing sa ple points which are not entirely' qualified for severe accident scenarios.
Su ::arv p '
Fcr the reasons cutlined above, TVA reco== ends that the Sequbyah unit 2 full power license be conditioned to require i=ple=entation of the
. p6staccident sa pling requirements bercre startup following the first refuel'ing outage.
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TABLE I FOSTACCIDENT SAMPLINC
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Date Sackcound March 28, 1979 TMI Accident July 1979 frJREG-0578 issued
~
- January 24, 1980
. Justification for emergency purchase approved January 25, 1980 Postaccident equipment procurement specification for Browns Ferry, Sequoyah, and *n'atts Bar issued February 1, 1980 Co =on design criteria issued for all plants Ap,ril 10, 1980 Revised cor=on design criteria for all plants April 30, 1980 Sentry Equipment contract signed July 3. 1980 It'A entered into Subagreement No.
with the.
Department cf Energy (DOE) sp,ecifically Oak Ridge '
National Laboratory (OPR.) to gain technical-expertise *related to PAS 4
- /
4!'
Septe=ber 1980 Advance notice of NUREG-0737 received from NRC Nove=ber 1980 ITJbG-0737issuedbyNRC l
Dece=ber 1980
- Regulatory Guide 1 97, revision 2, was issued by
.NRC (see note below)
February 24, 1981 DetaiieddesigncriteriaissuedforSequoyah
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May 1951 Problems with the use of the existing radio-
, chemical laboratory at Sequoyah were identified July 22, 1981 TVA determined that the HVAC for the Sequoyah
~
sample station will have to be revised August 27, 1981 Readjustment; in the design basis for the l
radioche=ical laboratory and sa ple station at Srquoyah were co:pleted UO'TE :
Replatory Guide 1.97 deals with the " type" and " category" requiresents of instruments that are % f ecction during and following an accident.
. staccident sa:pling instrumentati:n fills into type "D measuring
".ariables that provide information to.Lndicate the cperation of individual safety systems and other systems important to safety."
The system whose variables,are being m'easure) then. determine what the
" category" of the instruments should be.
Regulatory Gud.de 1 97 goes into detail concerning " types" and " categories."
Eegulatory Guide 1.97 i=pacted the design schedule, but it aided.TVA in caking a decision to lower the classification of so=e of the piping and l
valves which resulted in some cost savings.
wi.
O ADDITIONAL ACCIDENT MONITORING INSTRUMENTATION NUREG-0737 ITEM II.T.1 Item II.T.1 of NUREG-0737 requires utilities with operating plants or plants under construction to add and/or upgrade instrumentation associated with accident monitoring by January 1, 1982 (or initial fuel loading, I
whichever is later).
TVA is proceeding to purchase and install this equipment on an expedited basis.
However, in some areas, proble=s have
' ~
develeped in our design and procurement work for Sequeyah which will make the January 1, 1982, i=plementation date for this instrumentatien difficult to meet. The following is a technic *al su==ary on the current status of these efforts:
Wide Range Noble Gas. Iodine and Particulate Effluent Monitors i
I.
General Co=ments
~
Wide range noble gas monitors which meet regulatory requirements 1.
are available from a number of vendors (such as General Atomic, Eberline, etc.).
~
2.
RG 1 97 and NUREG-0737 c.11 for particulate and iodine sampling j
as well as noble ga's.
A monitor which. accomplishes particulate, iodine and noble gas monitoring and meets regulatory requirements is not presently available.
3.t Nobl'e gas monito'rs presently available (as mentioned in 1 Wove) require a sampling asse=bly for the vents.
The monitor ssse=bly often is as large a's 6' x 3' x 4' and weighs as madh as 5000 lbs.
Some presently.available models make provisions for taking particulate and iodine grab sa=ples.
1 4.
Installation of a noble gas asse=bly now'and adding a particulate and iodine capability as it becomes available will require an additional space and'likely an additional isokinetic sa=pling
~
' asse=bly for each vent sampled.
II.
TVi's Intent 1.
Provide a noble gas =enitoring capability which covers the ranges required by RG 1.97 and NUREG-0737 and which a"e IEEE Class 1E, seis=ic Category I, and qualified to the enviro : ment in which they are located.
2.
Procure an integrated monitoring asse=bly which will acco=plish particulate, iodine and noble gas monitoring per regulatory requirements.
The isokinetic sa=pling task can be acco:plished with one probe assembly and one control panel assetbly.
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