ML19207C084
| ML19207C084 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/10/1979 |
| From: | Wilson R GENERAL PUBLIC UTILITIES CORP. |
| To: | Arnold R GENERAL PUBLIC UTILITIES CORP. |
| References | |
| NUDOCS 7909060423 | |
| Download: ML19207C084 (3) | |
Text
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i Inter-Office Memorandum g-i Date May 10, 1979
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Sub,ect Long Term Reactor Coolant System Pressure Control To R. C. Arnold Locanon Three Mile Island The current plan is to take the reactor primary system down t..
pressure of approximately 300 psi for long term (2 -
4.+ months) natural circulation.
This pressure is preferred since it does not cause addition l_ gas to be re - -- -
drawn from the co_ntrol rod drives and provides ample margin on ircore thermo-
~
couple T In all probability, the reactor coolant system temperature will alsobe$#Idatitsapproximatelycurrentvaluebyperiodicthrot'lingofthe condenser bypass valve.
During the 2 - 4 or more months that the reactor is expected to be on natural circulation cooling, there are five potential options for pressure control.
These include:
1.
Use of the pressurizer with a normal vapor bubble.
2.
Taking the plant solid and controlling through makeup and letdown.
3.
The new pressure volume centrol system.
4.
Floating the plant cn core flood tanks.
5.
Floating the plant on the low pressure injer.tien pump discharge.
The sixth option, letting the system pressure drop to atmospheric, is not viable in the near term.
The attached table summarizes some of the pros and cons of the various alternatives.
It is recommended that pressure control be maintained through normal pressurizer heating with a vapor bubble. This recommendation assumes that current efforts to retain / restore heaters will be successful, that solid operation will not show a marked change in system leak rate and that system makeup and letdoun can be secured after periodically taking the pressurizer solid and letting the system drif t down on leakage. On going solid, Pzr level can be obviously benchmarked.
In the event that unforeseen problems or other restrictions prohibit operating the pressurizer in the normal mode, it is recommended that the first fallback position be to take the plant solid and maintain pressure through normal makeup and letdown (assuming valves, pumps, etc. permit). The second fallback position
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e 00 9060 GPU Service Corporat:cn :s a subsid.ary of General Pub 5c Utit.es Corporabon
Long Term Reactor Coolant System Pressure Page Two should be use of the new pressure volume control system.
Floating of the core flood tanks or the low pressure injection pumps should be considered as further fallback positions, although neither of these systems appear to be technically unacceptable.
R. F. Wilson RFW/a1 ATT cc:
J. C. Herbein L. Pler.ke - B&W E. G. Wallace D. Vollmer - SRC J. P. Moore M. P. Morrell B. D. Elam G. Kulynych - B&W 4
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LONG TERM REACTOR COOLANT SYSTUI PRESSURE C0 Z DOL USE CF THE PRESSURIZER TAKING Tile PLANT SOLID AND NEW PRESSURE VOLUME CON ~IkOL FLOATING THE PLANT ON FLOATING THE PIANT ON Tli,F.
WITH A NORMAL VAPOR BUBBLE CONT ROLI.I t THP,0 UGH MAKEUP SYSTEM CORE FLOOD TANKS 14W PRESSURE INJECTION i
AND lETIK?,
Pl'HP LISCHARCE END I
a l
ADVANTAGES.
Normal plant operating System has been demonstrated System completely redundant System basically passive Uses instal ed plant j
mode - maximum operator I
except for makeup of flood equipment i
familiarity Electrical heaters not System accessible for tank war.
i required maintenance System is redundant System ' '.th vapor bubble System is redundant - no j
is forgiving and has a Uses normal plant modifications required low time response equipment Permits adequate boron Leakage rate is probably no Protects against up and down
. control worse than any other pressure transients No l Par chemistry problem systen Has capability of ta :Ing a
pressure upsurge as well as downsurge j
Low pressurizer level heater alarm circuit and ability i
l to track level lends i
confidence l
i Chemistry control in j
pressut'zer adequate DISADVANTAGES:
Requires some heater Constant operator attention New system, probably a lot Reactor system must be Kiximum pressure is I
capability - probably required of bugs, and will require solid saproximately 175 psi 200-250 kw extensive operator Response time require.1 short familiarity Flood tanks do not provide System is active and Requires active HP! pumps
'l thrust pressure high pressure over-protec-requires continuous and valves on a periodic transients accentuated System provides protection tion, must still rely on operation of pumps basis against pressure loss, but code safeties.
Large pressure breakdown Requires almost cont inuous over-pressure protectiun Decay heat removal across -alve may cause operation or cycling of still by primary and code Adjustment of system train is unavailable wear-out unless makeup makeup pumps and letdown safeties.
pressure possible but and letdown periodically l
awkward High recirculation secured.
Active components contaminated, flow required on the maintenance may be impractical pumps.
I Secures seal injection flow ifpsets cause water surging Chemical addition other than 1oron must be done through to reactor coolant pumps from pressurizer to main coolant loop, may cause makeup pump natural circulation upsets.
Finite possibility of Same concern with long nitrogen injection into Q
time reliability due to the primary coolant system; h.
high pressure breakdown however, possibility is across valve and wear out small in absence of IDCA O
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