Water chemistry of nuclear reactor systems 7 : proceedings of the conference organized by the British Nuclear Energy Society and held in Bournemouth on 13-17 October 1996

447 Pages·1966·13.745 MB·English

W a t er c h e m i s t ry of
nuclear r e a c t or s y s t e ms 7
Proceedings of the conference organized by the
British Nuclear Energy Society and held in
Bournemouth on 13-17 October 1996
British Nuclear Energy Society, London
ISBN: 978-0-7277-2565-3
Contents
Papers
Advances in water chemistry control for BWRs and PWRs. C. J. WOOD
Dose reduction measures at the Millstone Point - 2 PWR. M. J. B. HUDSON and
H. OCKEN
Influence of extended cycles on reactor coolant chemistry and collective dose at
Nuclear Power Plant Beznau. H. VENZ and U. WEIDMANN
Study on improvement in shutdown chemistry for radiation exposure reduction in
nuclear plants. A. ITO
Investigation of iron deposits on the fuel assemblies of the Loviisa 2 VVER-440
reactor. R. J. ROSENBERG, J. LIKONEN, R. ZILLIACUS, R. TERASVIRTA, M. HALIN
and S. SUKSI
The deposition of cobalt on in-core surfaces during boiling heat transfer.
N. ARBEAU, R. H. CAMPBELL, M. S. GODIN and D. H. LISTER
Characterization of colloids in primary coolant. M. BOLZ, W. HOFFMANN,
W. RUEHLE and F. BECKER
PWR in-pile loop studies and PWSCC susceptibility tests for improving the primary
water chemistry. N. OGAWA, T. NAKASHIBA, M. YAMADA, K. KASAHARA,
R. UMEHARA, Y. ARIMOTO, S. OKAMOTO and T. TSURUTA
Assessment of reactor primary coolant sampling data under steady full pow T
operation. J. BRUNNING, P. CAKE, A. HARPER and P. K. TAIT u/
Influence of the initial surface condition on the release of nickel alloys in the primary
circuit of PWRs. L. GUINARD, O. KERREC, D. NOEL, S. GARDEY and F. COULET
Development of Li meter for PWR plants. Y. TSUZUKI, Y. KONNO and F. FUKUDA
Reduced sulphur species in the PWR primary loop as consequence of cationic resins
ingress. Ma. S. GARCIA, D. GOMEZ-BRICENO, F. HERNANDEZ and A. LAGARES
CVCS resin management procedures: options for the Sizewell B design. J. C. BATES
and M. E. PICK
Poster Paper
Lithium and boron effects in the corrosion mechanism of zirconium alloys under
coolant chemistry conditions. N. RAMASUBRAMANIAN
Experiments with Couette autoclaves for the investigation of activity uptake in the
oxide layer of stainless steel under boiling water reactor conditions. A. HILTPOLD
and H. LONER
Water chemistry control in BWR reactor loop. J. KYSELA, J. SRANK and P. VSOLAK
On the corrosion mechanisms in an experimental PWR irradiation facility.
P. M. A. DE BAKKER, M. VERWERFT, M. WEBER and E. DE GRAVE
Corrosion product measurements at Ringhals 1. J. BRUNNING, P. CAKE,
B. BENGTSSON, G. GRANATH and J. KVINT
A survey of coolant pH versus radiation fields for Westinghouse PWRs.
M. V. POLLEY, K. GARBETT and M. E. PICK
Combined chemical degassing and oxygenation of reactor coolant at Koeberg Nuclear
Power Station. K. J. GALT, M. W. ADENDORFF, N. B. CARIS and A. WELSH
Investigation of the colloid characteristics in the water of boiling water reactors.
C. DEGUELDRE, E. SCHENKER and H. NOBBENHUIS-WEDDA
High temperature thermodynamics of metal ions and oxides-zinc ions and related
compounds. Y. HANZAWA, D. HIROISHI, C. MATSUURA, K. ISHIGURE, M. NAGAO
and M. HAGINUMA
Experimental study of cobalt up-take by trevorite and chromite with and without the
presence of zinc. L. PERMER and C. G. OSTERLUNDH
Corrosion and co-uptake behaviour on structural material in BWR primary coolants at
Zn and Ni addition. T. OSATO and Y. HEMMI
Effect of zinc addition on cobalt ion accumulation into the corroded surface of type
304 SS in high temperature water. M. HAGINUMA, S. ONO, K. TAKAMORI,
K. TAKEDA, K. TACHIBANA and K. ISHIGURE
Influence of zinc on properties and growth of oxide layers in simulated primary
coolant. J. PIIPPO, T. SAARIO, V. TEGEDER and B. STELLWAG
Prediction of N-16 steam transport in BWRs under hydrogen water chemistry
conditions. C. C. LIN
Experimental studies of radiolysis in an in-core loop in the Studsvik R2 reactor.
H. CHRISTENSEN, A. MOLANDER, A. LASSING and H. TOMANI
Kinetics in passivating oxide films. H.-P. HERMANSSON, M. STIGENBERG and
G. WIKMARK
Solubility of fuel crud in BWR. B. BEVERSKOG and I. PUIGDOMENECH
Formation of large monocrystals in BWR. B. BEVERSKOG, I. FALK and KAREN GOTT
Radiation chemistry of aqueous solutions of hydrazine and ammonia up to 200°C.
G. V. BUXTON, D. A. LYNCH and C. R. STUART
Water radiolysis: the influence of some relevant parameters in PWR nuclear reactors.
B. PASTINA, J. ISABEY and B. HICKEL
Papers
The KEMOX-2000 Project: minimizing radiation doses by optimizing oxide conditions.
T. KELEN and H.-P. HERMANSSON
Optimal water chemistry control of BWR cooling systems. K. OTOHA and
S. UCHIDA
Development of water chemistry optimization technologies in recent Japanese BWRs.
N. UETAKE, H. HOSOKAWA, S. UCHIDA, K. OHSUMI, T. TONE and N. SUZUKI
Corrosion product release during the shutdown of BWRs. E. SCHENKER, H. LONER,
H. p. ALDER, B. BLASER and W. BLASER
The history of water chemistry at Onagawa Unit-1 and Unit-2. K. KAWAMURA,
S. ABE, K. HONDA, K. GOTOH, T. YOTSUYANAGI, K. YAMAZAKI and
Y. MORIKAWA
The effects of water chemistry of cobalt deposition in BWRs. P. J. BENNETT,
P. GUNNERUD, J. K. PETTERSEN and A. HARPER
The mitigation of IGSCC of BWR internals with hydrogen water chemistry.
R. L. COWAN
Model calculation of water radiolysis and electrochemical potentials in BWR primary
coolant III. R. M. KRUGER, G. ROMEO, J. HENSHAW and W. G. BURNS
Model calculations of water radiolysis in the primary coolant circuit of the Barseback-
1 BWR. K. LUNDGREN and H. CHRISTENSEN
Effects of HWC water chemistry on activity transport in BWRs. C. B. ASHMORE,
D. J. BROWN, A. M. PRITCHARD, H. E. SIMS and C. C. LIN
Evaluation of hydrogen water chemistry effectiveness on materials in reactor
pressure vessel bottom of a BWR. N. ICHIKAWA, Y. HEMMI and J. TAKAGI
Evaluation of effects of water radiolysis on zircaloy corrosion in BWR simulation loop.
E. IBE, N. ICHIKAWA, S. SHIMADA, T. KOGAI, Y. ISHII, C. VITANZA, C. C. LIN,
B. CHENG and Y. NISHINO
Poster papers
Studies of oxide deposition in boiler flow control orifices. D. J. MORRIS and
I. S. WOOLSEY
An assessment of the blanket coolant chemistries in the SEAFP-M2 fusion device by
the CORA-NNC code to reduce operational radiation exposure. S. M. ALI
Prefilming for steam generators. N . ENGLER, P. COLIN, P. SAURIN, H. JOUBERT,
C. BRUN, B. SALA, I. BOBIN-VASTRA, P. COMBRADE and M. THIRY
Iodine behaviour in the primary circuit during cold shutdown in PWR. J. 6. GENIN,
C. LEUTHROT, A. HARRER, A. CARAMEL and J. P. BRETELLE
PWR secondary system chemistry modelling using the EPRI PWR secondary
chemistry simulator. T. M. GAUDRAU, G. D. BURNS, A. D. MILLER and
P. J. MILLETT
Development of a new evaporator using hydrophobic membrane for radioactive liquid
waste. T. IZUMIDA, K. MAKOTO, K. FUNABASHI, H. KUROKAWA and
M. MATSUDA
The effect of residual chemical decontamination reagent on SCC susceptibility of
type 304SS. S. TAKAYAMA, H. HIRABAYASHI, M. YAJIMA and S. TUJIKAWA
Application of KWU antimony removal process at Gentilly-2. Y. DONDAR, S. ODAR,
H. ALLSOP and D. GUZONAS
Crud removal performance and application of developed ion exchange resins.
T. TONE, N. SUZUKI, Y. YOSHIZAWA, K. IIDA, K. HARAGUCHI and K. MAEDA
Non-invasive monitoring of corrosion in the light water reactor by optical methods.
H. P. ALDER, C. DEGUELDRE and E. SCHENKER
Characterization of material behaviour by means of simultaneous monitoring of water
chemistry and of surface film electric resistance. U. EHRNSTEN, J. LAGERSTROM,
T. LAITINEN, J. PIIPPO and T. SAARIO
Modelling of transport and deposition of corrosion production in primary circuits.
P. BELOUSCHEK, K. HOF, M. MAAS and S. NOWICKI
Evaluation of zircaloy corrosion under various water chemistries in a BWR simulation
loop. M. AOMI, T. KOGAI, S. SHIMADA, N. ICHIKAWA, E. IBE, Y. ISHII, B. CHENG
and D. LUTZ
Papers
Overview of zinc addition in the Farley 2 reactor. C. A. BERGMANN, R. E. GOLD,
J. SEJVAR, J. D. PEROCK, M. DOVE and R.S. PATHANIA
The effects of zinc addition on cobalt deposition in PWRs. P. J. BENNETT,
P. GUNNERUD, H. LONER, J. K. PETTERSEN and A. HARPER
The effect of zinc addition on cobalt accumulation on steel surfaces and its
thermodynamics. Y. HANZAWA, K. ISHIGURE, C. MATSUURA and D. HIROISHI
Modelling the effect of zinc addition on the uptake of cobalt oxide films in PWRs.
J. H. HARDING
The CORD UV CONCEPT for decontamination and the application experience.
H. WILLE and H.-O. BERTHOLDT
Recent chemical decontamination experience in EDF nuclear power plants. D. NOEL,
M. DUPIN, B. LANTES, H. B. SPYCHALA, F. GOULAIN, J. GREGOIRE, and
S. JEANDROT
In situ gamma spectroscopy monitoring of the full system decontamination efficiency
at the Loviisa NPP. V. TANNER, R. KVARNSTROM
KWU high temperature chemical cleaning process control. S. ODAR
Corrosion of carbon steel support structures at their intersection with steam
generator tubes during crevice cleaning. D. S. MANCEY
Secondary side boiler chemical cleaning field experience and process optimization to
limit weldmeht corrosion. K.-R. BRENNENSTUHL, S. CASERA, C. M. DANIEL,
J. P. KRASZNAI and E. P. MCNEILL
Optimization of secondary water chemistry in US PWRs. P. J. MILLETT and
F. HUNDLEY
The effect of the new feedwater distributor design on the impurity concentrations in
one of the Loviisa 2 unit steam generators. K. MAKELA, T. LAITINEN and
T. BUDDAS
Hideout text in Gravelines 1 and Dampierre 3 units. A. STUTZMANN, J. M. FIQUET
and M. BLAIN
Prediction and control of crevice chemistry in PWR steam generators.
S. G. SAWOCHKA, S. S. CHOI, K. FRUZZETTI, J. BATES, G. WARD and
P. J. MILLETT
Flexible condensate polishing operation at Koeberg Nuclear Power Station.
K. J. GALT, M. W. ADENDORFF and A. WELSH
French experience on OD IGA/SCC. F. NORDMANN and A. STUTZMANN 393
Study of hydrazine alternatives under UK AGR plant operating conditions.
A. RUDGE, I. S. WOOLSEY, G. G. LEWIS and J. D. TYLDESLEY 399
Secondary side electrochemical potential monitoring and the redox state of corrosion
products in Ontario Hydro Nuclear. M. E. BRETT, A. P. QUINAN, J. E. PRICE and
J. A. SAWICKI 407
Electrochemical potential monitoring at Duke Power's Oconee Nuclear Station Unit
Two. D. P. ROCHESTER, J. D. WALD, G. L. WARD and B. H. CYRUS 415
Studies of titanium additions to PWR secondary systems. A. MOLANDER,
P. TARKPEA, P.-O. ANDERSSON and L. BJORNKVIST 422
Application of titanium compounds for caustic induced IGSCC mitigation in PWR
steam generators. S. G. SAWOCHKA, E. C. OLSON, G. P GARY, S. LAPPEGAARD,
R. P. PEARSON and A. MCILREE 428
Establishing threshold conditions for lead-induced cracking of steam generator tube
alloys. M. D. WRIGHT 435
Advances in Water Chemistry Control for BWRs and
PWRs
C. J. W o o d, Electric Power Research Institute, Palo Alto, California, U SA
INTRODUCTION
Ehis paper is an overview of the effects of water
Figure 2: BWR CAPACITY FACTOR LOSSES
chemistry developments on the current operation of
nuclear power plants in the United States, and the DUET0C0RR0SI0N
mitigation of corrosion-related degradation processes
and radiation field buildup processes through the use of
-ilvanced water chemistry. Recent modifications in 20
water chemistry to control corrosion and reduce
• adiation fields are outlined, including revisions to the
EPRI water chemistry guidelines for BWRs and PWR
primary and secondary systems. The change from a
single water chemistry specification for all plants to a
set of options, from which a plant-specific chemistry
! rogram can be defined, is described.
Plant operators have had considerable success in
minimizing the impact of corrosion on nuclear plant
productivity and U.S. plant capability factors reached
an all-time high of 82.6% in 1995, compared to 71.7%
79 80 81 82 83 84 85 86 87 88 89 90 91 92 93' 94 95
five years earlier. In fact, the loss of output resulting
from corrosion damage forms has decreased in recent YEAR
years, as shown in Figures 1 and 2.
Despite the good performance recently, degradation of
Figure 1: PWR CAPACITY FACTOR LOSSES components as a result of stress corrosion cracking and
other corrosion processes continues to be a significant
DUET0C0RR0SI0N
concern to the operators of BWRs and PWRs, and is
potentially life-limiting in many cases. There are
indications of increased degradation, particularly in
BWR vessel internals and at tube/tube support plate
intersections in PWR steam generators, as plants age.
Advances in water chemistry have played an important
role in controlling degradation processes, and primary
chemistry improvements, together with other radiation
control techniques, have succeeded in reducing
occupational radiation exposures. As indicated in
Figures 3, total collective exposures at US plants have
declined at the same time as electric generation has
increased, resulting in a factor of 5 reduction in the
exposure/generation ratio over the past 15 years.
Figure 4 shows the trend in plant average exposures for
the same period. Although the rate of improvement
has slowed recently, and the annual averages fluctuate
from year to year, it can be seen that total collective
Water Chemistry of Nuclear Reactor Systems 7. BNES, 1996 1
WATER CHEMISTRY OF NUCLEAR REACTOR SYSTEMS 7
exposures in 1995 were the lowest since the 1970s, lessons learned from the latest operational experience at
when only a few plants were operating.. nuclear power plants worldwide.
FIGURE 3: US NUCLEAR POWER PLANT Evolution of the EPRI Guidelines
RADIATION EXPOSURES AND ELECTRIC GENERATION In the early years of commercial nuclear plant
operation, the main issue was controlling chemistry
El Total Roms h 8 within a fairly broad specification (typically the first
E3 MW:V edition of the EPRI Guidelines) to avoid off-normal
rem/MWy n n .6n
>- conditions that could result in serious materials
(1.4 J
m 3 degradation. During the early-mid eighties, the
specifications were gradually tightened as data became
£52s rw.lrllli 1.0 «« available from plant operation and research work
ho.« (typically Revision 1 of the Guidelines).
0.6
The "purer is better" approach resulted in a significant
•0.4
improvement in plant operation, but it was also clear
•0.2
that there was a need for further reductions in
corrosion-related problems [1].
More recently, chemists have been modifying the water
chemistry to control specific problems, usually
involving chemical additions to the cooling water. For
example, Revision 2 of the PWR Secondary Guidelines
included the options of morpholine and boric acid to
FIGURE 4: U.S. PLANT AVERAGE RADIATION EXPOSURES
control pH in the secondary system and to reduce
| caustic attack. Another example is the BWR Hydrogen
Water Chemistry Guidelines, published in 1988.
111111000000000000000000 J
v i | r • MMiRl PF Vt R
1 The range of options has increased further in the past
J
1 six years. Revision 2 of the PWR Primary Guidelines,
—, 1U,—J V^ I1 covered several elevated lithium/pH regimes, with more
|
\. 1 detailed assessment of the options in the 1995 revision
I
s [2]. Zinc injection was included in the 1993 revision of
the BWR chemistry guidelines, for use with or without
;J ^ >" {
hydrogen injection [3]. Revision 3 of the PWR
f " Secondary Guidelines introduced molar ratio control to
f reduce intergranular attack (IGA) and IGSCC of steam
00 , . generator tubing [4]. Also, ethanolamine and other
1990 1B92
YEAR 1994 1996 advanced amines have been added to the list of options
for pH control. With the multiplicity of chemistry
options currently available, the plant chemist now
Several factors contribute to the reduction in radiation
requires selection criteria for determining the optimum
exposures - including enhancements in radiation
chemistry for his plant [5].
protection practices, shorter outages and reduced
requirements for special maintenance and repair - but
Water Chemistry Optimization
the reduction in out-of-core radiation fields has played a
Ideally, a water chemistry specification should be
major role in the continuing improvements in this area.
established that minimizes all adverse effects, but in
practice conflicting requirements demand an optimized
Nuclear Power Industry Chemistry Guidelines
strategy or approach. This means that water chemistry
The EPRI water chemistry guidelines provide nuclear
parameters must be selected to mitigate the most
plant chemists with the specifications for water
important problem area, without worsening less
chemistry control parameters, and the technical basis
significant problems. The optimum choice may be
for these specifications. The guidelines are produced
constrained by plant equipment limitations, for
by committees of utility, vendor and other industry
instance, the size of water treatment plant.
specialists. Various organizations, including EPRI, have
on-going research programs in the chemistry area, the
These advanced water chemistries have not been
results of which are incorporated in periodic revisions
without their difficulties: each of these chemistry
to the water chemistry guidelines, together with the
2
WOOD
modifications has some negative side-effects, which The number of plants using hydrogen injection has
need to be factored into the decision-making process. increased dramatically recently, with the majority using
the higher levels of hydrogen required to protect vessel
This often involves plant-specific considerations, as internals. The increase in the number of plants using
shown, for example, by the wide range of increases in zinc injection is also noteworthy, as is the transition
radiation fields found when BWRs switch to hydrogen from natural zinc oxide (NZO) to zinc depleted in zinc-
water chemistry [6]. Generally, the benefits of reduced 64 (DZO). It is remarkable that the most popular
IGSCC far outweigh the downside, but in isolated cases chemistry regime for US BWRs involves relatively
the increased exposures have caused HWC to be high concentrations of hydrogen and depleted zinc
temporally discontinued. Another example: morpholine injection.
increases cation conductivity, which was a key
motivation for testing ethanolamine in PWR secondary Although the prime need has been to control IGSCC in
systems. In fact, accommodating these changes presents the recirculation piping system, the requirements of fuel
a continuing challenge to the industry. integrity and radiation control must be considered, also.
Electrochemical potential is the most significant
The philosophy behind the guidelines is evolving as parameter, but control of impurities is also important
chemistry becomes more complicated. Instead of "one for minimizing crack growth rates. There is a growing
rule for all plants", the guidelines have to accomodate rate of implementation of hydrogen water chemistry,
several options. Taking PWR secondary chemistry as originally used to control stress corrosion cracking of
an example: in contrast to the near-universal "all- recirculation piping, and now being applied, with
volatile treatment" (AVT) of a few years ago, the plant higher hydrogen concentrations, to reduce cracking of
chemist now has choices of boric acid, high hydrazine, internal components in the reactor vessel. This is
morpholine, ethanolamine or other amines. Attention is discussed in greater detail in another paper at this
now focused on controlling chemistry in the crevices of conference [8]. There are options of different rates of
ihe steam generator. hydrogen injection, oxygen addition to control flow-
assisted corrosion in the feedwater system, zinc
The next sections review the issues covered in the injection (including depleted zinc-64) and iron/nickel
latest editions of the EPRI guidelines, including control to minimize radioactivity transients at
application of recent water chemistry improvements. shutdown, depending on specific plant design features.
BWR Water Chemistry The 1993 chemistry guidelines [4] combined the earlier
BWR plants are in a transition from normal normal water chemistry and hydrogen water chemistry
(oxygenated) water chemistry to hydrogen water guidelines, and provided a methodology for evaluating
chemistry to mitigate stress corrosion cracking, with the cost benefit of HWC for mitigating the stress
some plants using natural zinc to control radiation fields corrosion cracking of vessel internals. One of the key
and others depleted zinc to minimize radioactive zinc- objectives of the 1996 revision is to enhance guidance
65 formation [7]. Figure 5 shows the different on determining the level of hydrogen required to protect
chemistry combinations in use (or planned) for the crucial components. As the necessary amount of
second half of 1996. hydrogen is highly plant specific, and depends on the
location of components to be protected, a methodology
Figure 5: Number of BWR plants in USA using has been developed for estimating hydrogen
hydrogen water chemistry and zinc injection requirements and verifying that protection is indeed
obtained. A combination of benchmarking with in-core
measurements, modelling and monitoring is generally
used.
Other topics covered in the 1996 BWR Chemistry
Guidelines include improved guidance on controlling
feedwater iron ingress, and a revised section on zinc
injection. For both iron ingress and zinc injection, a
methodology for developing plant-specific programs
has been developed. Cost/benefit evaluations of
controlling iron depend on plant design and whether or
not HWC and/or depleted zinc are planned. There is
growing evidence that reactor water iron
concentrations below 0.5ppm increase cobalt-60
NWC Low HWC High HWC concentrations, which has resulted in several plants
with highly efficient cleanup systems, implementing
3
WATER CHEMISTRY OF NUCLEAR REACTOR SYSTEMS 7
iron injection, as has been practised in Japan for some Injection of natural zinc was partially succesful in
years [9]. reducing the rate of cobalt-60 buildup at Monticello,
but zinc-65 became the major source of radiation fields.
Plant experience with both natural and depleted zinc Depleted zinc has been used since the last chemical
injection has increased greatly in the past 3 years, and decontamination in 1993, with the result that radiation
there is now good data on radiation field benefits and fields on the recirculation piping have dropped to
costs. Depleted zinc is particularly beneficial in 200mR/h as the zinc-65 contribution declined. These
combating the increase in cobalt-60 levels observed results indicate the the transient increase in shutdown
vith moderate to high hydrogen injection rates, but the fields resulting from HWC can be controlled using
amount required depends on iron inventories. Figure 6 depleted zinc.
shows the effect of use of depleted zinc in LaSalle
BWR, a plant with forward pumped heater drains Main steam line radiation from N-16 activity is
operating under normal water chemistry conditions. increased under HWC conditions, because the nitrogen
With no zinc-65 activation, recontamination rates after species formed under reducing conditions are more
chemical decontamination have been greatly reduced. volatile than in oxidizing environments, with the
magnitude of the effect increasing at higher hydrogen
Figure 6: Effect of Injection of Depleted Zinc on concentrations. The operational impact of increasing
Radiation Fields of LaSalle 1 BWR steam line fields is usually considered during the
assessment of the level of hydrogen injection on a
Avg. Dose Rate (mR/hr) plant-specific basis. The increase in main steam line
600
operating dose rate has affected plants differently. In
Depleted some cases, only minor impacts are noted and they have
500
Zinc been dealt with by administrative actions. In other
Deccn Decon
plants, local shielding of turbine components has
400 j_ _ II
I reduced the impact to acceptable levels. The projected
impact of a 4-6 fold increase in main steam line
300
operating dose rates for protection of vessel internals
has curtailed plans for hydrogen injection at some
200
Decon I BWRs.
100
Recent studies have shown that the presence of noble
L..±. . i J I I I I I I I I I I I I I I I I I I I :l I I I I I metals on structural materials significantly reduce the
Jan Jan Jan Jan Jan Jan Jan Jan Jan
hydrogen concentration required to achieve the IGSCC
1982 1984 1986 1988 1990 1992 1994 1996 1998
protection potential of -230mV(.SHE). The noble
Another example of the effects of depleted zinc is metals could be applied as a constituent alloy, by
shown in Figure 7 for Monticello plant. This unit has plating or by thermal spray coating. Noble metal
experienced increasing hydrogen injection rates over chemical addition (NMCA) has significant advantages
the past eight years. for application to existing plants [10, 11], and is
currently being investigated as an in-situ method of
Figure 7: Effects of Hydrogen Water Chemistry and reducing the amount of hydrogen required to lower the
ECP on material surfaces, which would also mitigate
Zinc Injection on Radiation Fields at Monticello
the effects on operating radiation fields. A plant
Avg. Dose Rate (mR/hr) demonstration is planned to determine the effectiveness
1200 of the NMCA technique, the durability of the coatings
0.7 1.1 | 1.8 HWC and any effects on fuel performance and shutdown
1000 __PPnl__ ppm I ppm radiation fields.
Zinc
800 PWR Primary Chemistry
j :i Depleted
si Zinc
600 In the PWR primary system, the main interactions are
between the requirement to maintain radiation
400 exposures as low as reasonably achievable, which in
1
turn requires low radiation fields, the need to minimize
200 -- _______________ primary water stress corrosion cracking (PWSCC) of
New Pipe Decon s Decon?: Decon alloy 600 tubing and penetrations, and the need to avoid
: 1 1 L l i i •! i i i excessive oxidation of Zircaloy fuel cladding. In this
Jan Jan Jan Jan Jan Jan Jan case, pH and lithium and boron are the important
1985 1987 1989 1991 1993 1995 1997
parameters. Elevated lithium is required to maintain
4