ML17266A377
| ML17266A377 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/22/1980 |
| From: | Bernero R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17209A468 | List: |
| References | |
| ALAB-603, NUDOCS 8012230090 | |
| Download: ML17266A377 (7) | |
Text
e~p,% Itic;~
e aate4 0
UNITEDSTATES NUCLEAR REGULATORY COMMISSION lYASHlkGTON,D. C 20555 AUG 2> >BO ENCLOSURE i
~
r 0
~
~
rI HEHORANDUM FOR:
Harold R. Denton, Director Office of Nuclear Reactor Regulatfon THRU:
Thomas E. Fhrleg, Acting Director Office of Nuclear Regulatory Research FROM:
SUBJECT:
Robert M. Bernero, Director Division of Systans and Relfabf.lfty Research Office of Nuclear Regulatory Research ALAB DECISiON 603 DATED JULY 30, 1980 ON STATION BLACKOUT AT ST.
LUCIE UNIT 2 The pilose of this menerandIrII fs to offer corrnents on the recent ruling.
by the App al Board on St. Lucie 2 (ALAB-603).
Me do not agree Ath conclusion 4, 'that a complete loss of AC ~~erstation blackout-riust be, considered a desfgn basis event for St. Lucfe Unit 2.'laws are apparent in ALQ&603. fn a.number of areas:
The cpantftatfve crfterfon Rr actfan.
2.
The fbreclosure of,. alternatfves
.to deal fifth blackout.
3.
Assumption tha~t. Lucfe,g fs.exceptionally prone M blackout.
.'hese problmmreas are discussed further.below Ouantitatfve Criterion for Action It fs clear the criterion of-ac~eptabfllty,-.chosen'LABgp
.31..of, the decision) was-reve-intended by-the-staff to be applied fn such:
- e nay.
Section 3.$.3.of the Standard Review Plan explicitlyllm<te the use of the-10:- crfterfon-(areas of.rev5ex).to 'accidents fnvalvfng nearby fndustrfal, mflftary, and transportation facilities and potential accidents -fnvolv4eg:.hazardous~terfa1s~r acifvfties~-
the vicinity of the plant'.=-that ds,toexternal hazards such as.
nearby transportation of toxic-gases or-explosives.This fs not to...:~
say that a probability. goal fs not appropriate for station black-:.=:.--
out.
Station blackout lends ftself mare readily to a probabflfstfc goaT than do some other event sequences.
fhwgve~ believe-a.....:..
probabilfstfc goal fn the nefghferhood of 10 per plant-year
$s rare reasonable f'or a potentfal core damage accident resulting from station blackout.
As an interim ~al, for say 5.years, a range of 10
. to 10
.auld entaf1 a rIfnfmal risk at operating reactors
gaeol d. R. Denton
&2M pUG S2 SBO....
~
'hile a mre permanent probabflfstic staff ob)ectfve is developed.
- Indeed, improvements over the last 7 or 8 years in our knowledge of the severity of core damage accidents raise the question of whether. '.';,-
the 10 criterion mfght be.unnecessarfly restrfctfve even for external hazards.
Me recognize that there exfsts'o'riterion fn the record, so one can hardly blame the Appeal Board for somewhat arbftrarfly selecting Section 2.2.3 as thefr basis.
Clarification of the staff objective fs sorely needed, and we believe this should be a top prioritynot only for station blackout but for other important transients such a,s loss of feedwzter.
2.
oreclosure of Alternatfves The ALAS-603 conclusions do not provide foor what wo think fs an
~ acceptable alternative to making station blackout a design basfs event.
Dne alternative is to reduce the probzbflfty of a station blackout.
This could be done by improving the reliability of the
.'mergency onsite AC power supply system.
F'o r example, an additfona1 diesel generator (wfth diversity fn manufacturer, size, testing, etc.), or a gas turbine could make significant frprovment.
Another alternatfve auld be an NRC-approved plan and procedures for the restoration of offsfte ~wer and emergency onsfte power.
Ate that ALAB assumed the probability of restoring offsfte ~wer was zero and also that the probability of getting one of the diesel generators started {after initially failing to start) was zero.
Yet, the conclusion was drawn on page.69 that 'there fs a high likelihood.
~that Allowing station blackout, a source ef AC power can be restored before events resulting f'rom=fts loss produce reactor..core damage..'~
If the Board had.fncluded a probabf13ty for. AC. power restoration, we think (and their above-stated conclusion supports us) ft could d
tt 1*1 td ~.
g
-:1 I tdddgd&: 'll dll 1 1=-
by as much as a factor'of 10.
Approved'AC power resuratfon procedures could'also sfgnfffcantly limit the.'ime interval for'wh1chNtNs necessary to. assure.that%he decay%eat-rival systensmre independent of AC power.
~
0 Assumotfon that St. Lucfe fs Exceotionall Prone to Blackout There are at 1east two potentfal major fmpacts of ALAB-603 on the *'.'-
1fcensing process and on opeJ atfng-.,reactors~-.Ff rst -ff. the-conclusion ~
t t tl tt 1 t-t 1'-
d lg 1
\\*t-t t.dt. I *'I fs accepted, then-ft surely must be applied to other operating reactop since nast are fn the same probability range, f.e., 10 to 10 pei plant-year for experiencing a station blackout.
Current estfmates. of station-blackout probabf1f ty, Qsed-on-operatfng experfence, do not confirm the premfse that Florfda-based plant@ ---
are exceptionally prone to ihat event Compared to other plants fn
~
et
~
~
Harold R. Denton
&3M AUt: 2.2 580
~ the U.S, for example, the loss of offsfte power'at Florfda plants fs only a little care frequent (perhaps a'actor of 2) than the national average.
A crude survey of operatfng experience fndfcates to us that there are at least 8 plant sites with uare frequent 10ss of offsite ~wer than ~an of the Florida plants..
Thfs,enay be because different failure mechanfsms such as tornadoes, fce storms, lightning, electrical demand surges, grid relfabflfty, etc. are operating fn different geographical regfons.
Rr example, two of the higher frequency plants are fn the midwest (tornadoes?), ~
are on Mrthern great lakes (wfnds, fce, lightning?), three are nn the northeast seaboard (weather, grid ties, demand surges?)
and one fs near the Gulf of Fhxfco (weather, grid connection?).
- Thus, whfle grid relfabflf+ aay be somewhat lour for Florfda plants, a
number of other causes of power loss are rut present in Florida.
.Furthermore, the loss of, onsfte emergency AC ~wer does mt appear to be a strong function of geographical 1ocation.
Thus, Florga.
plants (including St. Lucfe Unit 2) auld not app ar to have inherent faflure mechanfms of their emergency AC ~wer that are p cu1far to
. the peninsular geography.
w7 A second ~ssfble impact could occur ff the application of the 3D'-
- criterion to a ~tentfa1 accident sequence (such as a station blackout transient) Ns accepted; ft might-then become"a precedent by whfch to 5udge other transients and LOCAs. It fs likely that no current or planned cattraercfa1 operating reactor could moet such a
.severe criterion.; The probability of core damage accidents due fn other trans Iant.and I.OC Ameqv ennes has.-tragventIy+en-estimatevI hy NRC over the last 8-years'to.. bo-fn-the.40= ta. 10
.range',at-.eperatfng
'eacto rs.
. In scary, whfle-we agree with much of-ALAB-603 and=feel-ftAs;a.weH-'ritten lucid presentatfon of the station blackout concerns, m do agree that staf:fon b1ackout must b considered a design basis event at Robert M. Bernero','>re tor.
-Ofvfsion of Systens-. and.-ReUahfl ftg.
Research Office of Nuclear Regulaury Researdf CC M. Payun, KD M. Olms ead, ELD'-
R. Bfrke1, NRR K. Knfel, NRR G. Edison, RES P. Baranows+,
RES F. Fbsa, NRR R. Fftzpatrfck, KRR P
ENCLOSURE 2 TO:
ALL LICENSEES OF OPERATING NUCLEAR POKER REACTORS AND APPLICANTS.FOR OPERATING LICENSES
~ l
SUBJECT:
EMERGENCY PROCEDURES AND TRAINING FOR STATION BLACKOUT EVENTS A recent decision by the Atomic Safety Licensing and Appeal Board (ALAB-603) concluded that station blackout (i;e., loss of all AC power) should be considered a design basis event for St. Lucie Unit 2.
An amendment to the Construction Permit for St. Lucie Unit 2 was subsequently issued'on September'8, 1980.
The HRC staff is currently assessing station blackout events on a generic basis (Generic Task A-44).
The results of this study, which is sched-uled to be coaqleted in 1982, will identify the extent to which design pro-visions should be included to reduce the potential for or consequences of a station blackout event.
However, the Board has recoamended that mre imam diate measures be taken to ensure that station blackout events can be accormedated while Task A-44 is
'being conducted-Although we believe that, qualitatively, there appears to be sufficient time available following a station blackout event to restore AC pmer, we concur that some. interim measures should be taken.
.Consequently, we require that you promptly inclement interim emergency pro-cedures and a tr~ining program for.the. existing systems in youp facility.for station blackout. events, if such procedures and training do not already exist-The emergency-procedures-should. consider; but are not -limited to:
a.
The actions and equipment necessary to maintain. the. reactor coolant inventory and heat repaval with only DC porter available,- including consideration of the unavailability of auxiliary systems such as ventilation and coaqonent-..coolQg
=--
- b. The estimated-limiting tim to restore&C power and its basis-c.'The actions for restoring offsite AC peer -in-the-event of-a-loss of the grid.
- d. The actions for restoring offsite AC=power when.its, loss is due to-postulated onsite equi pment fai3ures.-..
- e. The actions necessary to restore emergency onsite AC pater-The actions required to restart 'diesel generators should-include-consid-eration of the unavailability.of AC.power.
For exaoqle, unsuccessful-..
attenpts to start diesel generators may result in depletion of the.
conpressed air'tanks.
After repairs or adjustments, further.attests to start.the diesels may not be possible without recharging the air tanks.
In the absence of AC pmer, provisions may-be-necessary for-portable air tanks, manual air pumps, DC cooqressors, etc..
- f. Consideration wf.the availability of emergency lighting-and-any--
actions required to provide such lighting, in equipment areas-where- ---.
operator or maintenance actions may be necessary.
I g.
Precautions to prevent equipment damage during the return to normal operating conditions following restoration of AC power.
For example, the limi.ations and operating sequence requirements which must be followed to restart, the reactor coolant pumps following an extended loss of seal injection water should be considered in the recovery procedures.
The annual requalification training program should consider the emergency procedures and include simulator exercises involving the postulated loss of all AC power and decay heat removal accomplished by natural circulation and the steam-driven auxiliary feedwater system for PWR plants, and by the steafii-driven RCIC and/or HPCI and the safety-relief valves in BWR plants.
We require that the actions described above be completed by June 1, 1981 for the licensed nuclear power reactors and plants licensed before that date, or prior to licensing for plants licensed after that date.
The staff's review of these actions will be accomplished as part of the implementation of the
..recomnendations which evolve from Task A-44 and implementation of the long-term programs related to emergency procedures and training in the TMI-2 Action Plan
{HUREG-0660).
The interim procedures developed in response to this request.
will eventually be placed by the final procedures which evolve from Tasks I.C.1.{3) and I.C.9 of the TMI-2 Action Plan..
Accordingly, yursuantNo 1G. GFR.50.54{f) licensees. are requested-to furnish, - - --
within forty-fixe {45) days of this letter, confirmation that the implementation date of June 1,-1981-will be met.
For plants licensed. after this letter,.these actions and the implementation-schedule will be incorporated as license eon-
'itions.
In-the event:that-%he completion-.date. cannot be.met; furnish;a proposed-revised date,.justiVication-for the. delay, and any planned-compensatiiig safety actions during-the. interim...,After.-ourevaluation of your-response, the HRC staff
'lt k
B; y.t tl t-.
h-q i t
d are appropriately-enforceable;
-%his'may include; as needed, issuance of 'a Confirmatory or Show-Cause Order Darrell G. Eisenhut, Director Division of Licensing