ML19317G771
| ML19317G771 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/11/1976 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| TAC-6710, NUDOCS 8004010599 | |
| Download: ML19317G771 (4) | |
Text
... _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L 3
I
=
I O
DISTRIBUTION:
/
ACRS (16)
Docket fit v Dross Docket to.:
50-312 ORB #4 Rdg~
VStello KRColler TJCarter Sacraaento l'unicipal Utility Cistrict ATTH: iir. J. J. ':attinoe 0 ELD Assistant General Mana9er 01&E (5) and Chief Enoineer RReid 6201 S Street VRooney (2)
P. O. Box 15030 RIngram Sacranento, California 95813 EhhX Czech Gentlemen:
DEisenhut TBAbernathy RE: RAUCHO SECO i:UCLEAR GE!:ERATI!!G STATICH A nuiber of reported instances of reactor vessel overpressurization in Pressurized ila ter Reactor (PMP.) facilities have occurred in which the Technical Specifications inclenenting 10 Ci R Part 50 Appenaix G licitations have been exceeded. The najority of cases have occurred durino cold shutdown in which the prinary system has been in water solid conditions. These overcressurization events have been initiated by a variety of causes, inclecing the following:
(1)
Isolation of RHR syster/letdoyn systen while charginn to a water solio prinary sysic9,
(?) Therrial expansion following the starting of a nrinary coolant pump due to stored therral enerny in steaa cenerators, (3) In3dvertent actuaticn of safety injection accunnlators, and (4) Initiation of operatien of a reactor coolant pwo or a high pressure safety iniectic.n punp.
In essentially all of the events reporten, a single personnel error, couipnent malfunction or procedural deficiency has been sufficient to cause the event.
He belicve that aperepriate steps should oc taken prointly by all PW licensees to ciniaize the likelihood of additional occurrences of reactor vessel overpressorization. Tc that end we recently co,picted a series of nestings with several FJP licensees and USSS suppliers in which m dis-cussed the rencrted overpresscrization evants and assessed the reasures that are currently beina enloyed to either avoid or reduce the probability of sinilar occurrences, or to control the pressure transient to less than Espendix G licits. Examples of tnose neasures identified by the various l
a 1 1 ~.-.
7j. y -,-
(
800.4010Nj 7 p
THIS DOCUMENT CONTAINS POOR QUALITY PAGES
=m;.;
mm-Sacranento Municipal Utility m
~ 01 stric t (1)
Conplete avoidant'e of water solid conditions by either naintaining
~
a pressurizer steam, bubble or by providing a low pressure nitrogen
_gg blanket in the pressurizer when a stean bubble cannot be maintained, (2) Disabling High Pressure Injection and Safety Injection pumps by disconnecting electrical power supplies when at low prinary system
==
terpera tures, (3) Installation of dual setpoint pressurizer power relief valve (s) to provide protection against exceeding Appendix G linits while at low prinary system teaperatures, (4) flininization of time at water solid conditions and upgrading plant procedures to incluce appropriate warnings and cautions when such operations are necessary, and ng (5) Installation of relief valves in charging punp discharge lines with 7
a setpoint to provide protection against exceeding Appendix G limits.
~
lt was noted in our discussions with the PWR licensees that, for the saiority of those plants involved, not all potential overpressurization events would be prevented by the ueasures they had identified and that some of the remaining neasures may have undesirable effects on reactor sa fe ty.
riased on the inforoation gathered to date, we have concluded that all PWP. licensees should evaluate their syster designs to deternine the susceptibility to oys.rpressurization events. Specifically, you should provide tne following:
(1) An analysis of the Peactor Coolant Systen (RCS) response to pressure transients that can occur during startup and shutdown.
Any cesian rocifict.tions determined to be necessary to preclude exceeding Appendix C limits are to be incorporated in this analysis.
The analysis should include a plot of rressure es a function of tire until ternination of the event. The analysis should assune the nest liniting initial conditions (e.g., one RHR train operating or available for letdown, other co.iponents in normal operation when the systen is water solid such as pressurizer heaters and charging punas, and one or vore reactor coolant pinps in operation) with the worst single failure or operator error as the initiating event.
Justification should be provided for the ci:oice of liniting con-ditions and worst single failure or cperator errer assuned in the a n al"s i s,
.1 s
s l
l 1
t
====-
Sacranmito Danicipal Utility District (2) A description of those desien radifications detemined to be necessary, including equipeent eerfomance specifications and systen operational sequences.
The design basis used in the choice of equipnent should be included, and
=
(3) A scheoule for the prmpt inplenentation of the prcrosed design rodi fica tio ns.
The basic criteric to be applied in deternining the adequacy of over-pressurization protection are that no sinc!1e ec,uipnent failure er single operator error will result in Appendix G linitations being exceeded.
For those situations in which the necessary desion chances identified
=
cannot oc inplenented within the next few nonths, you snnuld identify short-tem rcasures to reduce the 1ihelihood tha t overnressuriza tion events will eccur in the intorin pericJ until the pernEcont design changes can be nade. Short tem measures should ce icentified separately for ic:mdicte implementation within the turns and conditions of your licence.
Short tern reasures nir;ht include some cccbination of, out vould not ce lioited to, the f oliceting sugestions:
(1) Procedural cn3nges to nininire the time in which the prinary systen is in a water solid condition, (2) Ungrading r<icting plant procedures and ad.1inistrativa controls to assure tht arropriate earninas and cautions are inclu:!cd to alert tPa operator '>henever the potar'.ial fer orinary systat overpressurizatic 1 exists, (3) ^rovice alaras and/or indications to alert the enerator therqver prinarv syete' pressure increases tomre M,encix
,lirits, (c ) Introducinc m.;crecy.71 ant.;o11fic::tions for pres,nre relict, 3rd in (b )
I".sion'Ft Of oGdiIlotCl perSenCOl to T:nD1 tor plW GTratiov, 10 ;$ UOIMr sali'.l.
.5 L
a
..l
~
1 E ]....f.
..j
=
Sacranento Punicipal Utility District
]
J:odifications to preclude or nininize the probability of reactor vessel everpressurization events are plant dependent and the examples given
.g..
nay or may not be adaptable to your specific systea design. Consideration nust also be given to the potential effects of both the short tem and es long tern neasures you consider to assure that other aspects of nuclear
==
safety are not cc, promised.
To verify compliance with Appendix G pressure-tenperature linits during startup and shutdown, you should assure that the appropriate instru.en-tation is installed to provide a continuous permanent record over the full range of both pressure and temperature. This instrumentation shculd be in service durinc long periods of cold shutdown as well as during startup and shutdown acerations. Reliance upon the plant conputer to reconstruct a pressure transient is not considered sufficient beceuse 9
of the likelihood of co:puter doventiae especially during plant shutdown conditions.
!!O renuest that you notify us within 20 days after receipt of this letter that you will provide all tne ~information requestea within 60 days or exclain why you cannot neet this schedule end prcvide the schedule that you will meet.
This request for gencric infornation was approved by GA0 under a blanket clearance nunaar D-180225 (R0072); this clearance expires July 31, 1977.
Sincerely,
, y.i T " M Robert U. Reid, Chief Operating Reactors branch f4 Division of Operatinc Reactors cc: Devid S. Kaplan, Secretary and General Counsel 6201 S Street Post Office Fox 15030 Sacramento, Cclifornia 95813 Eusiness and Danicipal Department Sacrarento City-County Library
=
628 I Street Sacra.nento, California 95014 A
4
//
DOR:0RB.
'.t >... DOR..:. 0.R.. B...1 ti.d., j..
.m=..-
VRooney: '
GZech...x..[. WReid.._ _
8/d/76..
..8/.1\\/76_... Eu./16 ur.
- Tc t-- ALC. tit (Rev. 9 53) AICM C240 W u. s. novenhu.nr p. mTmo orrects ser4.exe.nes
.g am.i..
.w.,