ML20150C269
| ML20150C269 | |
| Person / Time | |
|---|---|
| Issue date: | 05/04/1988 |
| From: | Reed G Advisory Committee on Reactor Safeguards |
| To: | Wylie C Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1930, NUDOCS 8807120390 | |
| Download: ML20150C269 (2) | |
Text
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..... wMMITTEE 00 RECElVBD COR SAFEGU ARDS, U.S.N.R.C.
May 4,1988sDVISORY COMMITTEE 0N REACIOR SAFEGU ARDS, U.S.N.Rf.
5 1988.
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m 51% uauls, MENORANDUM FOR:
C. Wylie, Chainnan AM
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ACRS Subcommittee ongy @ @ l# 4(#3 FROM:
G. A. Reed, ACRS Coh(ultant
SUBJECT:
G. A. REED DEFERRED QUESTIONS FROM THE B&W SUBCOMMITTEE MEETING ON MAY 3, 1988 As per your request and desire to send B&W the questions (concerns) they elected not to answer on May 4,1988, the following are tabulated:
1.
The PORY Issue The documents disclose that only a single PORV train (including a single M0 block valve) are used. This PORY is now set to relieve at 2450 psig and the documents disclose that oftentimes the block valve is closed. Two safety valves (assumed to be Code type spring loaded) are set at about 2500 psig, and these three valves repre-sent the "bleed" capacity of "bleed and feed" decay heat removal.
Bleed and feed decay heat removal is therefore carried out on a maximum system pressure basis - something about 2500 psig. Since maximum pressures and therefore more severe pressure differentials across the SG tubes are then caused coinciding in certain tran-sients with higher temperatures and the stresses of injected spray on some of the steam generator tubes, one must explore the issue of SG tube leak and its aggravation, which leads one to question the method of reasonably rapid depressurization of the primary system, which appears to be the single train non-redundant PORY system.
In j
the light of this and continuing ACRS concerns about CE System 80 reactors without any PORVs, we would like information on the type and reliability of the B&W system PORV. Be advised that we believe that some or all of the B&W plants have internal pilot-operated relief valves, and that we are concerned about operability impacts of hydrogen gas and boron in the vapor phase of the pressurizer.
Now that B&W has increased the set point of the PORY to 2450 psig and presumably lessened its number of actuations (actuations which can be beneficial to offsetting hydrogen and boron impacts) our concern is heightened with respect to PORY malfunctions.
2.
Issue of a "Running" System vs. a "Standby" System 1 B&W' claimed an advantage of their "bleed & feed" decay heat removal l system,sincehighpressuresafetyinjection(normalcharging)
^
pumps and the system of valves and pipes are lined up and running.
They said this was superior to the compared to other PWRs where HPSI was on "standby". The industry has wrestled with this "run-ning" system vs. "standby" for a long time and a clearly accepted position on the best mode would be important.
However, in 8807120390 880504 DR16:iAID ORIGINAL
-19 PDR C atifjed rq _ _
C. Wylie, Chainnan 2
declaring a system "running" one must be careful that this is truly so, since in an accident such as loss of outside AC, it is probably the case that the B&W (HPSI) make-up or charging pumps must trans -
fertoanothersourceofpowerprobablywithastopandrestart;g g
programing.
From B&W we would like to know if this is the cas y and was this considered in their claimed "running" system superi '
1; ority.
(Note we are aware that Oconee has large capacity hydro *a i f units which can possibly make the power supply transfer problem s
less complicated - so Oconee design should not be the basis of the response.)
3.
The B&W Hi-Set (hi-loop) vs. Low-Set (lowered loop) Steam Cenerator Issue The earlier B&W reactor systems (0conee, TMI, Crystal River, SMUD) were of the low-set steam generator design. However, the German built B&W reactor was designed with hi-set SG's as was later B&W l
units, Davis-Besse, WPPSS, and Bellefonte. Since the hi-set SG design is a much more expensive design (order of millions of dollars for the much taller containment) what were the reasons B&W shifted to the hi-set SG design? Was it related to the natural circulation issue that has been raised. Was it related to customer insistence, (for instance, the Gennans) and what were the customer's reasons for justifying the more expensive design?
4.
The No Steam Stop Valve Issue and Vapor Containment Size Some B&W reactors (0conee, Rancho Seco, and TMI) either do not have Main Steam Line Stop Valves or have slow closing (locally operated) valves.
Perhaps these same plants either do or do not have steam line non-return valves, but this is imaterial to the issue of a steam line break inside containment since there would be no valve redundancy to assure the interruption of steam flow to the break.
The question that arises from this design situation is whether or not the containment designs factored in the primary and secondary side blowdown heat loads in this accident and the heat loads from the subsequent operational actions that would be necessary to bring the plants to safe shutdown? In answering this question it would be helpful if B&W could itemize sequentially the operational actions that would be taken to arrive at safe shutdown, or arovide us with a typical plant Emergency Operating Procedure for t11s accident.
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